Hot-dip galvanized steel strip

Transcription

Technical Terms of Delivery
voestalpine Stahl GmbH
www.voestalpine.com/stahl
Hot-dip galvanized steel strip with zinc coating
6
Steel grades
6
Mild steels for cold forming
Structural steels
High-strength steels for cold forming
6
12
16
Micro-alloyed steels
17
Bake-hardening steels
22
High-strength IF steels
24
Dual-phase steels
28
Complex-phase steels
33
TRIP steels
35
Zinc coating groups
38
Surface39
Surface of the zinc coating
39
Surface quality
39
Surface type
40
Subsequent surface treatment
41
Available dimensions
42
Inspection and Testing
43
Test unit
43
Sample-taking
43
Performance of tests
43
Repeat tests
44
T echnic a l T e rm s o f D e l i v e ry • H o t-di p g a l v a ni z e d s te e l s tri p • 0 2 /2 0 1 2
Introduction5
2
Contents
45
Forming
45
Joining
45
Thermal rating
46
Suitability for the application of coatings
46
General notes
47
47
Fretting corrosion
Darkening
47
47
Formation of white rust
Flatness
49
3
Hot-dip galvanized steel strip with
zinc/iron-coating (Galvannealed)
48
Processing information
Steel grades
ZF coating groups
49
50
Surface51
Surface quality
51
Surface type
51
52
53
54
55
Joining
55
Forming
55
55
56
Fretting corrosion
56
56
zinc magnesium coating57
Steel grades
57
58
Terms of delivery
59
4
ZM coating groups
General notes
Surface72
Application and processing instructions
72
73
Appendix74
Pertinent standards
74
Hot-dip galvanized steel strip is a hot-dip refined product with Zn, ZnMg or ZnFe coating on both
sides. The corresponding short forms are Z, ZM and ZF.
Hot-dip refining is based on a modified Sendzimir process. This is a high-integration manufacturing
process that consists of the following main process steps: Cleaning the full-hard strip (dry cleaning
and/or cleaning with easy reducing furnace atmosphere), recrystallizing annealing, coating by dipping into a fusion-liquid bath and adjustment of the thickness with air or nitrogen blow-off, finishing
and/or straightening by stretching for the adjustment of mechanical properties, surface and flatness,
post-treatment, inspection and marking. All these processes run in continuous operation mode with
a continuous steel strip.
These Technical Terms of Delivery apply to hot-dip galvanized strip made of
p Mild steels for cold forming,
p Structural steels and
5
p High-strength steels suitable for cold forming.
Introduction
These terms of delivery are to provide information to the customer on the production program of our
hot-dip galvanizing lines at the Linz site and serve as a guideline for ordering and processing. In accordance with these Technical Terms of Delivery, hot-dip coated and galvanized steel strip complies with
generally applicable guidelines as described in the pertinent standards. You will find a comparison of
the standards in the Appendix.
Market requirements have reached a degree of complexity with regard to applications that would far
exceed the limitations of these Terms of Delivery if every detail were taken into account. For this reason we ask that you address any questions to your respective commercial or technical contact partner.
They will ensure that you receive an adequate answer.
The following contains a general description of the available steel grades and their respective areas
of application.The chemical constitution depends on the selected steel grade and is available upon
request. The mechanical properties, the available coatings and surfaces can be found in the respective tables.
DX51D (machine crimping quality)
is suitable for the production of simple shapes such as trapezoid shapes and corrugated iron sheets as
well as for simple manual forming procedures.
DX52D (drawing quality)
can be considered for complex sections, embossing and drawn components.
DX53D (deep-drawing quality)
is used for medium requirements on formability such as deep drawing.
DX54D (special deep-drawing quality)
is designed for the special requirements of formability and deep drawability.
DX56D (special deep-drawing quality)
is designed for the most demanding forming requirements.
DX57D (extra special deep-drawing quality)
was developed for extremely high forming behavior requirements, in particular for extreme deepdrawing strain and for the manufacturing of complicated press parts in rapid processing and highly
automated press lines.
The DX51D, DX52D, DX53D, DX54D, DX56D and DX57D steel grades are delivered according to
their mechanical properties. The values for the mechanical properties apply for a period of
p One month for steel grades DX51D and DX52D from the time they are made ready for dispatch
p Six months for steel grades DX53D, DX54D, DX56D and DX57D from the time they are made ready
for dispatch
Alternatively, agreement can be made on specific material properties for the manufacture of a particular component.
Steel grades
6
with zinc coating
Steel grade
DX51D
0.2% Yield
point 2)
Rp 0.2
[MPa]
Tensile strength Fracture elongation 4)
A80
Rm
[%]
[MPa]
min.
-
DX52D
140 – 300
DX53D
140 – 260
3)
Vertical
anisotropy 5) 6)
r
min.
Work hardening
exponent 5)
n10 – 20 (UE)
min.
Zinc coating
group
270 – 500
22
-
-
Z 70 – Z 600 7)
270 – 420
26
-
-
Z 70 – Z 600 7)
270 – 380
30
-
-
Z 70 – Z 600 7)
DX54D
120 – 220
260 – 350
36
1.6
0.18
Z 70 – Z 275
DX56D
120 – 180
260 – 350
39
1.9 5)
0.21
Z 70 – Z 275
DX57D
120 – 170
260 – 350
41
2.1
0.22
Z 70 – Z 275
5)
Values transverse to rolling direction.
2)
If the yield point is pronounced, the lower yield point ReL applies.
3)
This value applies only to re-rolled products (MB and MC surfaces).
4)
Minimum fracture elongation values are minimized by 2 units for product thicknesses of ≤ 0.7 mm.
5)
Warranty values for r are minimized by 0.2 for product thicknesses of > 1.5 mm and for product thicknesses of > 2.0 mm by 0.4.
6)
Values for r are minimized by 0.2 for product thicknesses of > 0.7 mm and n by 0.01.
7)
Coating profiles above Z 275 available upon request.
7
1)
Mechanical properties 1)
DX51D, DX52D
Available dimensions mild steels for cold forming
Ordered strip thickness (mm)
4.00
3.50
MC surface for automotive
industry not possible.
8
3.00
2.50
2.00
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
Ordered strip width (mm)
The graphics refer to thickness values with symmetrical thickness tolerances.
The maximum width is reduced by 20 mm if the width tolerance is limited or if the edge is cut.
Please contact our sales departments for widths below 900 mm (production scheduling for
center slitting and longitudinal slitting lines).
DX53D
4.00
3.50
9
3.00
2.50
2.00
1.50
MC surface up to a maximum of 1.2 mm in
thickness not possible for automotive industry.
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
DX54D, DX56D, DX57D
4.00
3.50
10
3.00
2.50
2.00
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
rolling. The tendency toward the formation of flow lines can occur once again after some time, for
which reason it is in the interest of the user to process the products as soon as possible. Freedom of
flowing figures on MB and MC surfaces is maintained for the following duration after the material
has been made ready for dispatch:
p One month for steel grades DX51D and DX52D
p Six months for steel grades DX53D, DX54D, DX56D and DX57D
Coil break freedom
Rerolling or straightening through product stretching may be necessary for specific coil break freedom
requirements. The order must specify any coil break freedom requirement.
It may be necessary to reroll the products in order to avoid the formation of flow lines during cold
11
Freedom of flow lines
through S350GD. These steel grades are suitable for all easy forming procedures such as crimping,
edging and profiling. They are not, however, intended for stresses such as those caused by deep
drawing. Depending on the strength class, the increased tendency toward elastic recovery during
the adjustment of machinery must be taken into consideration. Formability may be diminished
when these grades are stored for a longer period of time. Prompt processing after the material has
been made ready for dispatch is in the interest of the customer. The order must specify any coil
break freedom requirement.
Structural steels
Steel grade
0.2% Yield point 2)
Rp 0.2
[MPa]
Tensile strength 3)
Rm
[MPa]
min.
Fracture elongation 4)
A80
[%]
min.
Zinc coating
group
S220GD
≥ 220
300
20
Z 70 – Z 600 5)
S250GD
≥ 250
330
19
Z 70 – Z 600 5)
S280GD
≥ 280
360
18
Z 70 – Z 600 5)
S320GD
≥ 320
390
17
Z 70 – Z 600 5)
S350GD
≥ 350
420
16
Z 70 – Z 600 5)
1)
Values longitudinal to rolling direction.
2)
The upper yield point ReH applies when the yield point is pronounced.
3)
A maximum range of 140 MPa can be calculated for the upper limit of tensile strength.
4)
Minimum fracture elongation values are minimized by 2 units for product thicknesses of ≤ 0.7 mm.
5)
Structural steels are supplied with guaranteed minimum yield strengths in steel grades S220GD
12
Structural steels
S220GD, S250GD, S280GD
Available dimensions structural steels
4.00
3.50
13
3.00
2.50
2.00
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
S320GD
4.00
3.50
14
3.00
2.50
2.00
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
S350GD
4.00
3.50
15
3.00
2.50
2.00
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
In addition to the mild steels, high-strength steel grades with yield strengths ranging from 160 to 500
MPa are available and are suitable for cold forming with less forming stress as well as for very difficult
forming procedures. Based on specifically coordinated steel analyses and production conditions, various series of steel grades are available that lend themselves, depending on the steel grade, to specific
applications, particularly in the automotive industry. The higher yield point and the excellent forming
properties provide a significant potential for weight reduction.
The chemical composition of the substrate is adapted to the welding properties and is available
upon request. The maximum concentrations of base material elements correspond to the limit
values determined in EN 10346 for the respective grades (tables available in the Appendix).
The guaranteed mechanical parameters listed in the following sections are applicable to tests in
transverse direction to rolling. The mechanical parameters apply for a time period of three months
for all steels with guaranteed bake-hardening effect and six months for all other high-strength steel
grades from the time they are made ready for dispatch. Freedom of flow lines is guaranteed for this
16
period of time for Surface Type C orders. This does not apply to micro-alloyed steels.
High-strength steels for cold forming
The yield strength increased by the heat effect (so-called bake-hardening effect) is determined in
accordance with DIN EN 10325.
It can generally be assumed that increasing yield stress and decreasing sheet thickness lead to a
tendency towards necking, wrinkling and tears as a consequence of forming, which also leads to
form inaccuracy as a result of elastic recovery. In contrast with mild steels, the forming conditions
must be adjusted to the respective steel grade.
If the steel grades listed in the following sections do not fulfill customer requirements, please send a
material inquiry. Many high-strength steel grades are still being developed. More innovative developments will make additional steel grades available that have not yet been included in these Technical
Terms of Delivery.
Some of these steel grades have already been included in these Technical Terms of Delivery for information purposes only. Such products are delivered following technical review upon request.
the upper range of the conventional high-strength steel grade series and are suitable for moderate to
medium forming stress.
Steel grades HX260LAD through HX500LAD are generally based on the stability-increasing effect
of micro-alloyed additions (niobium or niobium with titanium). Grain refinement, age hardening and
the alloying of further strength-increasing elements, essentially manganese, are implemented in order to achieve the desired strength.
The main areas of application for micro-alloyed steels are structural components in the automotive
industry such as safety-related elements in the passenger compartment, side members or bumpers.
Micro-alloyed steels are also excellently suited for the manufacturing of high-strength special
sections. Upon special request, micro-alloyed hot-dip galvanized steel grades can be used as an
alternative in guaranteeing the mechanical parameters in longitudinal direction. In this case the
guaranteed range of yield strength correspondingly shifts to a lower range by around 20 MPa. The
tensile strength values also change to lower values for longitudinal samples by around 10 MPa. The
guaranteed value for fracture elongation is correspondingly raised by 1%.
Steel grade
0.2% Yield point 2)
Rp 0.2
[MPa]
HX260LAD
260 – 330
350 – 430
26
Z 70 – Z 600 4)
HX300LAD
300 – 380
380 – 480
23
Z 70 – Z 600 4)
HX340LAD
340 – 420
410 – 510
21
Z 70 – Z 600 4)
HX380LAD
380 – 480
440 – 560
19
Z 70 – Z 600 4)
HX420LAD
420 – 520
470 – 590
17
Z 70 – Z 600 4)
HX460LAD
460 – 560
500 – 640
15
Z 70 – Z 275
HX500LAD
500 – 620
530 – 690
13
Z 70 – Z 275
Tensile strength 3)
Rm
[MPa]
min.
Fracture elongation 4)
A80
[%]
min.
1)
2)
The lower yield point ReL applies when the yield point is pronounced.
3)
Lower minimum values by two percent are permissible for thicknesses of ≤ 0.7 mm
4)
Zinc coating
group
Refined micro-alloyed steels with a guaranteed yield strength of between 260 and 500 MPa cover
17
HX260LAD, HX300LAD, HX340LAD
Available dimensions micro-alloyed steels
4.00
3.50
18
3.00
2.50
2.00
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
HX380LAD, HX420LAD
4.00
3.50
19
3.00
2.50
2.00
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
HX460LAD
4.00
3.50
20
3.00
2.50
2.00
MC surface for automotive industry not possible.
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
Available dimensions upon request.
21
HX500LAD
coated bake-hardening steels that are characterized by their significant increase in yield strength
in the course of paint baking (bake-hardening effect). This increase in yield strength in the series of
steels from HX180BD to HX300BD is achieved by ensuring that a defined amount of carbon remains
dissolved in the steel.This carbon is released during heat treatment in the course of paint baking,
which leads to an increase in strength.
The hot-dip coated bake-hardening steels are also characterized by a very high degree of formability, which makes possible a wide range of applications in the manufacture of bodies in white.
Depending on the forming stress, the entire range of yield strengths can be used in interior components for bodies in white. The HX180BD and HX220BD steel grades are also especially suitable for
exterior bodies in white because the bake-hardening effect in these steels when compared to mild
steels yields significantly improved dent resistance.
Steel grade
0.2% Yield
point 2)
Rp 0.2
[MPa]
Tensile
strength
Rm
[MPa]
Fracture
elongation 3)
A80 min.
[%]
Vertical
anisotropy
r
min.
Work
hardening
exponent
n10 – 20 (UE)
min.
Bakehardening
value BH2
[MPa] min.
Zinc coating
group
HX180BD
180 – 240
290 – 360
34
1.5
0.16
35
Z 70 – Z 200
HX220BD
220 – 280
320 – 400
32
1.2
0.15
35
Z 70 – Z 200
HX260BD
260 – 320
360 – 440
28
-
-
35
Z 70 – Z 200
HX300BD
300 – 360
400 – 480
26
-
-
35
Z 70 – Z 200
1)
2)
3)
Lower minimum values by two percent are permissible for thicknesses of ≤ 0.7 mm.
By fine-tuning alloy compositions and adapting process parameters it is possible to produce hot-dip
22
HX180BD, HX220BD, HX260BD, HX300BD
Available dimensions bake-hardening steels
4.00
3.50
23
3.00
2.50
2.00
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
Hot-dip coated, higher-strength, interstitial-free steels are based on a vacuum-decarburized IF base
material stabilized with Ti and/or Nb, which leads to an ideal condition for extremely difficult forming
procedures with deep-drawing stresses. The adjustment of the required ranges of strength is carried
out by alloying P and Mn in the course of solid-solution strengthening. This basic IF analysis lends
this group of steel grades higher values of vertical anisotropy (r value) when compared to other steel
grades of similar strength. This vertical anisotropy value is an important parameter for deep-drawing
strain. The high r values in diagonal direction lead to a certain degree of isotropic behavior during the
forming of this series of steel grades.
The main area of application for high-strength interstitial-free steels is found in formed automotive
components, such as in the interior wheel arch, side members that are difficult to form, or in bottom
plates in the area of the tunnel. For this reason, profiling applications seem to be less sensible because
no deep-drawing stress occurs.
24
Steel grade
0.2% Yield point Tensile strength
Rp 0.2
Rm
[MPa]
[MPa]
Fracture
elongation 2)
A80
[%]
min.
Vertical
anisotropy 3)
r
min.
Work hardening
exponent
n10 – 20 (UE)
min.
Zinc coating
group
HX160YD
160 – 220
300 – 360
37
1.9
0.20
Z 70 – Z 200
HX180YD
180 – 240
330 – 390
34
1.7
0.18
Z 70 – Z 200
HX220YD
220 – 280
340 – 420
32
1.5
0.17
Z 70 – Z 200
HX260YD
260 – 320
380 – 440
30
1.4
0.16
Z 70 – Z 200
HX300YD
300 – 360
390 – 470
27
1.3
0.15
Z 70 – Z 200
1)
2)
3)
The guaranteed value is minimized by 0.2 units for product thicknesses > 1.5 mm.
HX160YD, HX180YD, HX220YD
Available dimensions higher-strength IF steels
4.00
3.50
25
3.00
2.50
2.00
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
HX260YD
4.00
3.50
26
3.00
2.50
2.00
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
27
HX300YD
Dual-phase steels consist of a multi-phase base material microstructure of which the main components are ferrite (80–90%) and martensite (10–20%). Other phases may be included in smaller
amounts.
The special characteristic of dual-phase steels is that particularly low yield ultimate ratios can be obtained with high ultimate tensile strengths. As related to the high level of tensile strength, high degrees of fracture elongation and hardening exponents can also be achieved. Because of pronounced
offset strain hardening, particularly at the beginning of forming, dual-phase steels are especially
predestined for forming stress in the stretch forming area. An additional positive characteristic is the
achievable bake-hardening effect, which leads to an additional increase in the yield strength after
forming during paint baking.
Based on the characteristic property profile of dual-phase steels, this series of steel grades is especially
suitable for crash-relevant structural parts such as side members, crossmembers, and stiffeners for A,
B or C columns. Dual-phase steels demonstrate special potential in significantly contributing to weight
reduction as well as increased passive safety in automotive structures.
28
Dual-phase steels
Dual-phase steels
Steel grade
0.2% Yield
point 2)
Rp 0.2
[MPa]
Tensile strength
Rm
[MPa]
min.
Fracture
elongation 3)
A80
[%]
min.
Work hardening
exponent
n10 – 20 (UE)
min.
Bake-hardening
value
BH2 [MPa]
min.
HCT450X
260 – 340
450
27
0.16
30
Zinc coating
group
Z 70 – Z 200
HCT500X
300 – 380
500
23
0.15
30
Z 70 – Z 200
HCT600X
340 – 420
600
20
0.14
30
Z 70 – Z 200
HCT780X
450 – 560
780
14
-
30
Z 70 – Z 200
HCT980X 4)
600 – 750
980
10
-
30
Z 70 – Z 200
1)
2)
3)
4)
HCT450X
Available dimensions dual-phase steels
4.00
3.50
29
3.00
2.50
2.00
MC surface for automotive industry available
upon request.
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
HCT500X
4.00
3.50
30
3.00
2.50
2.00
upon request.
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
HCT600X
4.00
3.50
31
3.00
2.50
2.00
upon request.
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
32
HCT780X, HCT980X
strength is a meaningful addition to the dual-phase range of steels. These steel grades are defined
with minimum yield strengths from 780 to 980 MPa. The microstructure of these advanced highstrength steels is characterized by the fact that the martensite particles are distributed in the soft
ferrite matrix, whereas bainite phases can also occur in addition to the martensite.
In comparison to the dual-phase steels, this series of steel grades is characterized by a higher yield
strength at the same tensile strength and thus a higher yield-strength ratio and a somewhat lower
possibility of guaranteeing certain levels of fracture elongation. The complex-phase steels are also
characterized by pronounced work-hardening behavior, even though this is not as noticeable as it is
with the dual-phase steels. The additional benefit that strength increases in the course of heat treatment during paint baking, remains as it does in dual phase steels.
Structural parts with lower forming stress show higher yield strengths with this series of steel grades
in comparison to the dual-phase grades. This can be compensated through a simpler component
design aimed at increasing strength resulting from stronger deformation. Partially martensitic steels
are predestined for high-strength special sections and safety-related structural components with lower forming stresses.
This grade also lends itself well to the manufacture of foldable parts and roll-formed components.
Steel grade
0.2% Yield point
Rp 0.2
[MPa]
Tensile strength
Rm
[MPa]
min.
Fracture elongation
A80
[%]
min.
Bake-hardening
value
BH2 [MPa]
min.
HCT780C 2)
600 – 750
780
10
30
Z 70 – Z 200
HCT980C
800 – 950
980
6
30
Z 70 – Z 200
2)
1)
2)
Zinc coating
group
The availability of complex-phase steel grades with increased yield point and minimum tensile
33
Available dimensions complex-phase steels
HCT780C, HCT980C
34
(approximately 10%) and metastable residual austenite (up to 15%). The hard phase (bainite) and stability of the austenite during forming influence the spectrum of mechanical properties.
Transformation-induced plasticity means that the metastable “soft” austenite is transformed into “hard”
martensite during plastic forming (deep drawing). This makes local constriction difficult and increases
the values for uniform elongation. This is the basis for the well-known excellent formability of TRIP
steels with high initial tensile strength of the respective basic strength. The increased bake-hardening
effect achieved by temperature treatment additionally increases the potential weight savings. This series of steel grades is available in two classes with minimum tensile strengths of 690 MPa and 780 MPa.
TRIP steels with 980 MPa are currently under development and can be delivered upon request. TRIP
steels are particularly suited to crash-relevant applications or safety parts with increased forming stress
in the manufacturing process.
TRIP steels
Steel grade
1)
0.2% Yield point
Rp 0.2
[MPa]
Tensile strength
Rm
[MPa]
min.
Fracture
elongation
A80 min.
[%]
Work hardening
exponent
n10 – 20 (UE) [MPa]
min.
Bake-hardening
value BH2
[MPa] min.
Zinc coating
group
HCT600T
400 – 520
600
25
-
40
Z 70 – Z 200
HCT690T
430 – 550
690
23
0.18
40
Z 70 – Z 200
HCT780T
470 – 600
780
21
0.16
40
Z 70 – Z 200
TRIP (transformation-induced plasticity) steels are comprised of a ferritic matrix (roughly 75%), bainite
35
TRIP steel
HCT600T, HCT690T
Available dimensions TRIP steels
4.00
3.50
36
3.00
2.50
2.00
MC surface for automotive industry
not possible.
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
Available dimensions TRIP steels
37
HCT780T
The desired zinc coating group (corresponds to the zinc coating in g/m 2 on both sides) is specified in
the order.
Coating groups
Zinc coating group
Zinc coating in g/m2 on both sides min.
Triple surface test
Single surface test
Zinc coating thickness in µm per side
Typical value
Area
Z 100
100
85
7
5 – 12
Z 140
140
120
10
7 – 15
Z 200
200
170
14
10 – 20
Z 225
225
195
16
11 – 22
Z 275
275
235
20
15 – 27
Z 350
350
300
25
19 – 33
Z 450
450
385
32
24 – 42
Z 600
600
510
42
32 – 55
A zinc coating of 100 g/m 2 (on both sides) corresponds to a zinc layer thickness of approximately
7 µm per side. The respective possibilities for delivery, depending on the steel grade, are shown in
the steel grade tables.
The Z350–Z600 zinc coating group can only be delivered with an NA surface.
Special coatings are available upon request in special cases only.
Different zinc coating for each side (different degree of galvanization) can be delivered upon request. In the event of differential galvanizing, in consequence of production, the surface of the side with
the lesser amount of zinc coating may have a different appearance than the side with the greater
amount of zinc coating.
The zinc coating is monitored continuously by means of an x-ray fluorescent technique.
The available zinc coatings and their respective minimum values are shown in the following table.
38
Zinc coating groups
The surface of the zinc coating is determined by the design, type and surface treatment. Hot-dip
galvanized steel strip Zn with surface NA and chemically passivated is delivered in the event the
order does not contain any additional information on the desired surface. Possible dimension-related
limitations with respect to the surface can be found in the limit curves.
The zinc coating does not include intentionally added lead concentrations (lead-free hot-dip galvanized strip). Finally, with respect to the environmental compatibility of the product, this measure was
implemented by voestalpine Stahl GmbH and excludes the delivery of hot-dip galvanized strip with
distinctive spangle formation (large spangles).
Surface quality
Normal quality (N)
Zinc crystals occur in varying brightness and size, depending on prevalent galvanizing conditions.
The usability of the product is not influenced by these crystals. The grade is delivered even if no preferences regarding surface quality are specified. We reserve the right to ship rerolled material.
Small spangle (M)
The surface shows small to macroscopic non-visible spangles caused by targeted influence on solidification. The products may show a slightly different body structure on the surface from coil to coil
and as well as in one coil. Delivery of slightly rerolled strip in surface type MA (explicitly not desired
by the customer) must be specified in the order.
Zinc coating surface
39
Surface
Typical surface A
Small pits, different spangle sizes, dark spots, stripe-shaped marks, and small passivation defects are
acceptable on this type of surface. Straightening and bending fractures and zinc runoff waves may
be visible.
Improved surface B
This type of surface is attained by rerolling. A small number of fractures in stretch forming direction,
finishing imprints, scratches, impressions, spangle structures, zinc runoff waves and slight passivation errors may occur on the inspected side. The uninspected side of the material must at least meet
the requirements of Surface Type A.
Best surface C
This type of surface is also attained by rerolling. The inspected side does not negatively impact the
uniform appearance of a paint coat. The other side of the material must at least meet the requirements of Surface Type B. Surface Type C is available for delivery up to a maximum of 1.5 mm.
Roughness
As a standard, Surface Types B and C are delivered with a medium roughness value ranging between 0.6 and 1.9 µm. Determination of the mean Ra roughness value is subject to a wavelength limit
of 2.5 mm in accordance with EN 10049 (standard length of 12.5 mm).
Where specially required, the delivery of limited roughness values may be specified. Special qualities
include smooth, half mat or mat.
Roughness
Design
Median roughness value Ra (µm)
Standard
0.6 – 1.9
Special design: smooth
0.9 max.
Special design: half-mat
0.6 – 1.4
Special design: mat
1.0 – 1.9
The desired quality must be specified in the order. Discussion of requirements with regard to surface
appearance is recommended when a smooth surface has been selected. Smooth surface with glossy
appearance (especially smooth) is subject to specification in the order.
There are three different surface types.
40
Surface type
pensity toward white rust. The following surface treatment procedures are usual:
p Chromium-free passivated (C)
p Oiled (O)
p Chromium-free passivated and oiled (CO)
Chromium-free passivated (C)
To the extent not specifically agreed, hot-dip galvanized steel strip is delivered with normal surfaces (NA) with small spangles (MA) and chromium-free passivated. Local discoloration caused by
chromium-free passivation is permitted and does not negatively influence other quality properties.
Chromium-free passivation may influence further surface treatments carried out by the customer, for
example phosphating. Another surface treatment is recommended in such cases.
Oiled (O)
Surfaces MB and MC are usually delivered in oiled condition. The oil layer can be removed with
suitable zinc-sparing degreasing agents. Depending on the intended treatment stress, two different
standard coatings can be ordered: slightly oiled as a temporary form of corrosion protection and as
a forming aid for medium forming stress, oiled for very heavy forming stress. Although the oil is
distributed evenly, a certain degree of oil will invariably spread across the length and width of the
strip and some oil from heavily oiled strip will be shed from the surface during transportation and
storage. This is technically unavoidable.
Oil amounts
Slightly oiled
approx. 0.7 g/m2 per side
Oiled
Chromium-free passivated and oiled (CO)
This combination of surface treatment can be agreed upon where increased protection against white
rust or oiling as a means to aid in forming is required.
Hot-dip galvanized steel strip is delivered only with surface protection on account of the increased pro-
41
Thickness
[mm]
1)
Width
[mm]
≥ 0.45
≤ 3.5
≥ 600
≥ 0.45
≤ 3.5
> 800
≥ 0.45
≤ 3.5
≥ 900
≤ 800
1)
< 900
1)
≤ 1600 2)
Maximum outside diameter
[mm]
Inner diameter
roughly [mm] 3)
Coil weight
[t] max.
2000
600
-
2000
600
-
2000
600
32
Width range between > 800 and < 900 mm only upon request.
2)
With limited width tolerance of 1,580 mm max.
3)
Inner diameter of 500 mm upon request.
Hot-dip galvanized steel strip in coils
42
The products can be delivered with or without any test of compliance with the requirements of these
Technical Terms of Delivery and/or ordering standards.
Material test certificates
In the event a certificate is desired, one of the test certificates defined in EN 10204 is subject to agreement at the time of the order.
Test unit
Specific tests are restricted to a test unit of 20 tons or a portion of 20 tons of hot-dip galvanized steel
strip of the same rolling unit. In the case of strip, a coil of more than 20 tons is considered as a test unit.
Scope of testing:
43
For each test unit, a series of tests is conducted to determine the following:
p Mechanical properties
p Coating adhesion
p Coating weight
Sample taking
Rolls from which samples are taken remain a constituent of the order. The right to select samples from
sheets is reserved by the employee responsible for the delivery certificate.
Performance of tests
Substrate testing
The tensile test is conducted in accordance with EN 10002-1 with samples of Form 2 (sample width
w = 20 mm, initial measured length L0 = 80 mm). Samples of mild steels, high-strength steels suitable for cold forming and advanced high-strength steels are taken crosswise with respect to the direction of rolling at a distance of at least 50 mm from the product edges. Structural steel samples are
taken in the longitudinal direction of rolling.
The zinc coating is generally determined in the course of a continuous and non-destructive test.
The zinc coating is generally determined in the course of a continuous and non-destructive test.
The following procedure is followed for special tests and in cases of arbitration. The samples for the
gravimetric test of the zinc coating are taken across the width of the strip (see Figure 1). The samples
can be round or square and must have a surface of at least 50 cm 2. The gravimetric test is carried
out in accordance with the methods described in EN 10292, EN 10326, EN 10327 and EN 10336. The
weight of the zinc coating is determined during this test by chemical dissolution of three samples taken from an area of distribution across the width of the strip. The final value is the arithmetic mean
derived from the three surface samples. The lowest value from the three surface samples is the value
for the single surface sample.
50
44
Figure 1: Gravimetric test
Zinc coating test
50
b/
2
b/
2
50
Strip width B
Zinc adhesion test
Zinc coating adhesion is determined in a drop-ball impact test in accordance with SEP 1931/version
1991. Judgment is made based on a qualitative standard series, whereas the criterion of quality is
based on proper workability according to the respective application.
In cases of arbitration the zinc test is carried out by means of a bending test in accordance with
EURONORM 12. The diameter of the bending block or bending roll is applied in accordance with
Table 5. The bending angle is always 180°. The sample legs are pressed together in such a manner
that the coating is not damaged.
Repeat tests
EN 10021 applies. Repeat tests on coils are carried out at a distance of at least one coil turn, however
from 20 meters at the most from the end of the strip.
steel strip. Our technical staff members are at your disposal to answer any of your questions.
Forming
Depending on the particular grade of hot-dip galvanized strip, it can be used for conventional forming processes such as edging, bending, curling, flanging, stamping, crimping, roll-profiling, stretch
forming and deep drawing. The selection of materials depends on the demands on formability as well
as the final geometry and function of the work piece. The zinc coating and the surface are adapted to
the processing parameters. The properties of the zinc require that the drawing gap and the retraction
radius are enlarged in certain cases as compared to uncoated thin sheet. Altered flow behavior makes it necessary in some cases to adapt the hold-down force in forming processes.
Joining
Conventional thermal and mechanical joining and gluing processes are used as connecting techniques, some of which, however, require adaptation of the processing parameters in order to take
into account special physical and chemical properties of the coatings. Hot-dip galvanized steel strip
is suitable for welding with common welding techniques. Special adjustment of the welding parameters and electrodes is necessary for this material when resistance welding (spot, projection or
stitch welding) is used. Thin zinc coatings simplify the welding process. The fumes generated during
welding should be exhausted. Corrosion protection in the welding area is optimized by means of a
suitable post-treatment process (such as zinc dust paint coating). Hot-dip galvanized sheet can be
soft-soldered or brazed. A metallically clean surface is a precondition that can be achieved with suitable fluxing agents. Proper filling of the joint is achieved with respective brazing metals. Corrosive
fluxing agents are to be carefully washed off after soldering. Mechanical joining techniques such as
screwing, riveting, crimping, flanging and clinching are not problematic and have the advantage that
they preserve the surface and maintain the anticorrosive properties. It is necessary to consider possible problems of contact corrosion when different materials are combined.
The significance of metal gluing is increasing in combination with other methods of joining. Highstrength connections are achievable with modern adhesives, even between oiled sheets. An examination of the surface systems, possible treatment processes and the adhesives themselves is advisable.
The following brief instructions are intended to provide assistance in processing hot-dip galvanized
45
roughly 200–250 °C. Temperature stress that lasts longer than this can lead to negative effects in the
substrate and surface materials because of the diffusion reaction between the zinc coating and the
substrate.
Hot-dip galvanized steel strip in all of its surface grades lends itself well to the application of organic
coatings (such as paints or films). Surface MB or MC is the correct selection in the event of high or
higher demands on a uniform surface appearance after coating. Proper pretreatment is required in
order to achieve perfect adhesion. Surface phosphating pretreatment in the works provides an excellent base for the adhesion of conventional organic coatings as long as the surfaces are clean.
Structural parts made of hot-dip galvanized steel strip can undergo long-term heat treatment up to
46
Thermal rating
Mutual friction between strips of hot-dip galvanized steel during transportation can cause dark spots
on the zinc surface. These affect the appearance but do not adversely affect the quality of the corrosion
protection. The tendency toward fretting corrosion can be minimized by oiling the hot-dip-galvanized
steel strip.
Darkening
Hot-dip galvanized steel strip is generally intended for short-term processing. The degree of surface
darkening may vary when these grades are stored for a longer period of time. This affects the appearance of the surface but does not adversely affect corrosion protection.
When hot-dip galvanized steel strip is subjected to humidity for a longer period of time with reduced
ventilation, a loose, mat gray to reddish material called white rust forms on the surface. Wide areas of
the material are attacked particularly when condensation water forms and wetness occurs between the
sheets or the coil layers.
There is no danger of white rust forming as long as the coils are stored properly. Temperature changes
during transportation and storage are critical.
Fretting corrosion
47
General notes
Example 1: Strip temperature of 8 °C, room temperature of 21 °C, relative humidity of 55%
Example 2: Storage area of 19 °C, relative humidity of 50%
Temperature (°C)
Relative air humidity
40%
25
danger of white rust.
minimum strip temperature of 11 °C required.
50%
60%
70%
100%
1
20
2
15
Diagram used to determine danger of white rust caused by condensation
48
10
Area of condensation
5
0
-5
Flatness
The strip is placed under tension when it is coiled. This tension causes deviations in the flatness of the
strip when it is downcoiled. A suitable straightening machine must be used to achieve flat condition of
the strip when delivered in coils. In some cases it improves the flatness of the material when paper inserts are applied during coiling. These are marked by flags placed on the end face. If paper inserts are
not desired or permitted, please specify this in the order.
Hot-dip galvanized steel strip is a hot-dip refined product with Zn or ZnFe coating on both sides.
The strip is subjected to heat treatment immediately after being galvanized. The zinc coating reacts
with the substrate material and forms a ZnFe coating with approximately 8–12% Fe.
This manufacturing process was the forerunner of the generally known product name
GALVANNEALED (= GALVanized and ANNEALED).
Steel grades
All steel grades described in the section entitled Hot-dip galvanized steel strip are available with the
exception of complex-phase and TRIP steels.
49
The same guarantees apply to mechanical parameters, with the following exceptions:
zinc/iron-coating (Galvannealed)
p Statistical values lower by two units apply to the minimums for mild steels from grade DX54D and
high-strength steels.
p The guaranteed r values are decreased for all steel grades by 0.2.
p The guaranteed n90 value for steel grades DX56D and DX57D is decreased by 0.01.
The available dimensions are limited to a thickness range of 0.5 to 2.0 mm.
Zinc Coating in g/m2 on both sides min.
ZF coating group
Triple surface test
Zinc coating thickness in µm per side
Single surface test
Typical value
Area
ZF 80
80
70
5.5
4 – 10
ZF 100
100
85
7.0
5 – 12
ZF 120
120
100
8.0
6 – 13
A ZF coating of 100 g/m2 (on both sides) corresponds to a ZF layer thickness of approximately 7 µm
per side.
Coating groups
50
ZF coating groups
Surface quality
Surface quality R
Hot-dip galvanized steel strip with a zinc/iron coating is characterized by a mat gray surface that is
free of spangles.
Surface type
Typical surface A
Small pits, dark spots, stripe-shaped marks, and small passivation defects are acceptable on this type
of surface. Straightening and bending fractures and runoff waves may be visible.
Improved surface B
This type of surface is attained by rerolling. The inspected side may be characterized by a small
number of occurrences of fractures in stretch forming direction, finishing imprints, scratches, impressions and slight passivation errors. The uninspected side of the material must at least meet the
requirements of Surface Type A.
Best surface C
This type of surface is also attained by rerolling. The inspected side does not negatively impact the
uniform appearance of a paint coat. The other side of the material must at least meet the requirements
of Surface Type B. Surface Type C is available for delivery up to 1.5 mm.
Roughness
As a standard, Surface types B and C are delivered with a medium roughness value ranging between 1.0 and 1.9 µm. Determination of the mean Ra roughness value is subject to a wavelength limit
of 2.5 mm in accordance with EN 10049 (standard length of 12.5 mm).
Hot-dip galvanized steel strip with a zinc/iron coating is delivered in Surface RA, RB and RC.
51
Surface
iron coating. Galvannealed can be delivered upon request in chromium-free passivated (C) or chromium-free passivated and oiled (CO). Depending on the defined micro-topography, difficult forming
stresses may make it necessary to increase the oil coating.
Oil amounts
Oiled
Heavily oiled
Hot-dip galvanized steel strip with a zinc/iron coating is normally delivered with an oiled (O) zinc/
52
Thickness
[mm]
1
Width
[mm]
≥ 0.50 1)
≤ 2.0
≥ 600
≥ 0.50
1)
≤ 2.0
> 800
≥ 0.50 1)
≤ 2.0
≥ 900
≤ 800
2)
< 900
2)
≤ 1600 3)
Maximum outside diameter
[mm]
Inner diameter
roughly [mm]
Coil weight
[t] max.
2000
600
-
2000
600
-
2000
600
32
) Thicknesses below 0.5 mm only upon request.
2)
Width range between > 800 and < 900 mm only upon request.
3)
With limited width tolerance of 1,580 mm max.
Hot-dip galvanized ZF hot-rolled strip in coils
53
product-specific testing methods. It is advisable to agree on adhesion quality before materials are
ordered.
In general as with hot-dip galvanized steel strip. The adhesion test is conducted by means of special
54
In addition to the general information under hot-dip galvanized steel strip, the following applies to hotdip galvanized steel strip with a zinc/iron coating:
Joining
The information applies as for hot-dip galvanized steel strip. Welding behavior can be expected to generally improve. Particularly longer electrode tool life is achievable with resistance spot welding.
Forming
The zinc/iron coating has a strong tendency toward abrasion in powdered form based on the higher
strength during heavy forming, especially flattening stress. This tendency toward abrasion is primarily
55
dependent on the coating group. For this reason we generally recommend a low coating group.
Based on its specific surface structure, hot-dip galvanized steel strip with a zinc/iron coating after
proper cleaning is suitable for direct painting.
Mutual friction between strips of hot-dip galvanized steel during transportation can cause dark spots
on the zinc surface. These affect the appearance but do not adversely affect the quality of the corrosion
protection. The tendency toward fretting corrosion can be minimized by oiling the hot-dip-galvanized
steel strip.
When hot-dip galvanized steel strip is subjected to humidity for a longer period of time with reduced
ventilation, a loose, mat gray to reddish material called white rust forms on the surface. Wide areas of
the material are attacked particularly when condensation water forms and wetness occurs between the
sheets or the coil layers.
There is no danger of white rust forming as long as the coils are stored properly. Temperature changes
during transportation and storage are critical.
Fretting corrosion
56
General notes
the highest degree of corrosion resistance and excellent processing properties.
Hot-dip galvanized steel strip with zinc magnesium coating is manufactured in continuous hot-dip
coating lines. Aluminum and magnesium are alloyed in the zinc bath, thus creating a metallic
coating that dramatically increases cathodic corrosion protection in the salt-spray test.
Steel grades
All steel grades described in the section entitled Hot-dip galvanized steel strip are available upon
request with the exception of dual-phase, complex-phase and TRIP steels.
The same guarantees apply to mechanical parameters, with the following exceptions:
p Statistical values lower by two units apply to the minimums for mild steels from grade DX54D and
high-strength steels.
p The guaranteed r values are decreased for all steel grades by 0.2.
p The guaranteed n90 value for steel grades DX56D and DX57D is decreased by 0.01.
Hot-dip galvanized steel strips with the new coating made by voestalpine Stahl are characterized by
57
zinc magnesium coating
Coating groups
Zinc coating 1) in g/m2 on both sides min.
Layer thickness
1)
ZM 70 2)
ZM 90
ZM 120
ZM 150
ZM 200
ZM 275 2)
Coating profiles for the automotive industry available upon request.
Currently available minimum and maximum zinc magnesium layer thickness. Maximum and minimum coating thicknesses
vary depending on the steel grade and dimensions. Coating profiles above ZM 200 available upon request.
2)
Amongst others, these proven processing properties of hot-dip galvanized steel strip are also achieved
for hot-dip galvanized steel strip with zinc magnesium coating:
p Welding suitability
p Paintability and
58
p Formability
ZM coating group
There are no limitations with respect to processing properties.
zinc magnesium coating:
p Limit dimensions and forming tolerances in accordance with EN 10143
p Technical Terms of Delivery in accordance with EN 10346
p SEW 022
You will find a list of applicable standards in the Appendix.
The following standards generally apply to hot-dip galvanized steel strip with
59
Terms of delivery
DX51D, DX52D
4.00
3.50
60
3.00
2.50
2.00
ZM 70-150
1.50
1.00
ZM 70-200
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
Dimensions and coatings for the automotive industry available upon request.
DX53D, DX54D, DX56D, DX57D
4.00
3.50
61
3.00
2.50
2.00
ZM 70-150
1.50
1.00
ZM 70-200
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
S220GD, S250GD
4.00
3.50
62
3.00
2.50
2.00
ZM 70-150
1.50
1.00
ZM 70-200
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
S280GD
4.00
3.50
63
3.00
2.50
2.00
ZM 70-200
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
S320GD
4.00
3.50
64
3.00
2.50
2.00
1.50
ZM 70-200
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
S350GD
4.00
3.50
65
3.00
2.50
2.00
1.50
ZM 70-200
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
HX180YD, HX220YD
4.00
3.50
66
3.00
2.50
2.00
ZM 70-200
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
HX260YD
4.00
3.50
67
3.00
2.50
2.00
ZM 70-200
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
HX180BD, HX220BD, HX260BD, HX300BD
Available dimensions bake-hardening steels
4.00
3.50
68
3.00
2.50
2.00
ZM 70-200
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
HX260LAD, HX300LAD, HX340LAD
4.00
3.50
69
3.00
2.50
2.00
ZM 70-200
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
HX380LAD, HX420LAD
4.00
3.50
70
3.00
2.50
2.00
1.50
ZM 70-200
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
HT440CMD
Available dimensions carbon-manganese steel
4.00
3.50
71
3.00
2.50
2.00
ZM 70-200
1.50
1.00
0.50
0.00
700
800
900
1000
1100
1200
1300
1400
1500
1600
Oiled (O), chromate-free passivated (C) or chromate-free passivated and oiled (CO).
NA, MA and MB
72
Surface
processing and storage of hot-dip galvanized steel strip with zinc magnesium coating as one would for
hot-dip galvanized steel strip.
Especially when forming hot-dip galvanized steel strip, conventional emulsions must be used with
an alkalinity of not more than 9. Nor may the constituents of the emulsion have any negative effect
on corrosion resistance. Several emulsions have been tested by voestalpine and approved for forming purposes.
It is also recommended that strip is used and stored in a manner that allows water and moistness to
be shed and in which periods of dryness are guaranteed so that the material can dry and not be permanently exposed to water.
Contact corrosion is to be avoided by electrically insulating different types of metals (with different
electro-chemical potentials) from each other.
The product properties described herein are applicable to the extent that hot-dip galvanized steel strip
with zinc magnesium coating is used and processed in accordance with the pertinent standards, the
Technical Terms of Delivery published by voestalpine and the information contained herein.
Further useful information is available in Reference Sheet 121:2003 published by “Steel Information
Center – Corrosion protection systems for structural elements made of steel sheet”.
In order to achieve optimum results, it is important to follow the instructions for the application,
73
Application and processing instructions
DIN EN ISO 12944-2: Corrosion protection of steel structures by protective paint systems
DIN EN 10143: Continuous hot-dip coated steel sheet and strip – limit dimensions
and forming tolerances
DIN EN 10346: Continuous hot-dip coated steel flat products – Technical Terms of
Delivery
DIN 55634:Coating materials and coatings – Corrosion protection of supporting thinwalled steel building components
ÖNORM M 3126:Continuous zinc magnesium-hot-dip galvanized flat steel products
SEW 022:Continuous hot-dip coated steel flat products – Zinc magnesium coatings –
Technical Terms of Delivery
Reference Sheet 121:2003:
Corrosion protection systems for structural elements made of steel sheet
Pertinent standards
74
Appendix
Technically more advanced. Successful together.
voestalpine Steel Division – the partner you can trust.
High-quality materials are the basis for our products. We strive to be the best partner for our
customers and want to provide them with the best-possible solution. We focus our expertise
on two aspects:
The personal aspect, with dedicated and highly competent employees
The technical aspect, with high-quality methods, products and services.
The companies in the voestalpine Steel Division and their employees understand partnership
to be the following:
Understanding for their customers’ business
Expertise and reliability
Responsibility for satisfactory project completion
Partnerships based on trust
Many years of successful partnerships with our customers prove our point.
voestalpine Stahl GmbH
voestalpine-Straße 3
4020 Linz, Austria
T. +43/50304/15-8007
F. +43/50304/55-8007
marketing_stahl@voestalpine.com
www.voestalpine.com/stahl

Hot-dip galvanized steel strip

Transcription

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