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WORLDWIDE
ENGINEERING
STANDARDS
Material Specification
Metals
GMW
Hot Dip Zinc Coatings for Sheet Steel
© Copyright 2008 General Motors Corporation All Rights Reserved
February 2008 Originating Department: North American Engineering Standards^ Page 1 of 9
1 Scope
This standard covers the requirements for hot dip coatings, both galvanized and galvannealed, applied to a sheet steel substrate utilizing a continuous hot dip process. The substrate may be cold or hot rolled sheet steel. Additional requirements or agreements shall be specified by regional GM Automotive Operations (GM) business units [e.g., North America (GMNA), Europe (GME), Latin America (GMLAAM), and Asia Pacific (GMAP)]. 1.1 Material Description. The type of coating and its mass and finish are specified by suffixes added to the basic specification number. The first two letters HD will designate a continuous hot dip coating. The coating mass for each side is designated by a minimum value in g/m^2. Only coating masses shown in Table 1 shall be used unless Materials Engineering is consulted. Other coating masses shall follow the same designation method. The letter G designates a pure zinc coating (galvanized) and the letter A designates a zinc-iron alloy (galvannealed) coating. The first set of digits along with the letter designation specifies the coating parameters of the unexposed side. The remaining designation specifies E (exposed), Z (semi-exposed), U (unexposed), or T (temper- rolled). 1.2 Symbols. Not applicable. 1.3 Typical Applications. Sheet metal parts consisting of steel grades as described in GMW2M, GMW3032M or GMW3399M. 1.4 Remarks. Not applicable. 1.5 Finish Suffixes. 1.5.1 Exposed (E). A finish produced by eliminating all visual spangle pattern and surface defects per paragraph 3.1.3.3, to be used for critical appearance applications. 1.5.2 Semi-exposed (Z). A spangle free finish produced by minimizing surface defects per paragraph 3.1.3.3 is used for secondary visible surfaces that do not require an exposed quality finish.
1.5.3 Unexposed (U). A minimum spangle finish used for non-critical appearance applications. See paragraph 3.1.3.3. 1.5.4 Temper Rolled (T). This surface shall have sufficient temper rolling such that luders lines or stretcher strain will not show when formed and painted. All other requirements are the same as U surface described above.
2 References
Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. ASTM D1876 ISO 7438 EN 10049 ISO/TS 16949 ISO 1460 SAE J ISO 4587 2.2 GM Standards/Specifications. 9984001 GMW B 440 0648 GMW B 040 1270 GMW B 440 1271 GMW GM3624M GMW GM6180M GMW GME 60410 GMW GMW2 GMW GMW11 GMW GMW3001 GMW GMW3011 L 000 0058 GMW3032 L 000 0726 GMW3059 L 000 0728 GMW3399 L 000 0780 GMW4795 LTP.ME. 2.3 Additional References. Auto/Steel Partnership Weld Quality Test Method Manual (AZ-017-02295 1.0C RI).
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GMW8 GM WORLDWIDE ENGINEERING STANDARDS
© Copyright 2008 General Motors Corporation All Rights Reserved
Page 2 of 9 February 2008
3 Requirements
The following paragraph defines specific requirements for material on delivery, processing, performance, and other stages during life cycle. 3.1 Requirements on Delivery. 3.1.1 Chemical Requirements. 3.1.1.1 Free Zinc Coatings. The coating produced shall consist of pure zinc and only minimum alloy layer. Pure zinc coatings may contain 75 ppm maximum cadmium and 100 ppm maximum lead, and must meet the requirements of GMW3059. The coatings shall not contain trace elements that are detrimental to adhesive bondability, phosphateability or paintability. 3.1.1.2 Zinc-Iron Alloy Coatings. The coating is produced on a continuous hot dipped galvanizing line followed by a thermal treatment. The zinc-iron alloy shall be a completely alloyed coating. This product is not spangled and has the tendency to powder when severely formed. For this reason, the bulk iron content of the coating shall be 8 to 12% by mass, when tested per GMW4795 or other regionally accepted specification, in order to eliminate flaking problems. Zinc-iron coatings may contain 75 ppm maximum cadmium and 100 ppm maximum lead, and must meet the requirements of GMW3059. 3.1.1.3 Base Metal. The sheet steel base metal chemical composition shall conform to the requirements specified in GMW2, GMW3032, or GMW3399.
3.1.1.4 Surface Treatment. Products coated with a designated lubricant (e.g., mill oil or prelube) shall comply with GMW14019. 3.1.2 Mechanical Requirements. 3.1.2.1 Coating Bend Test. All bend tests shall be conducted in accordance with ISO 7438. For all steels supplied according to GMW2 and GMW3032 (with 0.2% offset yield strength < 500 MPa), a 0T (Zero T) bend test shall be performed. Test specimens of coated metal shall be capable of being bent through 180 degrees in any direction without flaking of the coating on the outside of the bend only. For steels supplied to GMW3032 with 0.2% offset yield strength
500 MPa and all GMW3399 grades, the steel must be capable of a 90 degree test in any direction with a maximum test radius (r) related to the steel thickness (t) without flaking on the outside of the bend. Refer to Appendix B for maximum bend test radii for each grade and a diagram of the test setup. For testing of all steels, flaking of the coating within 6 mm of the edge of the bend test shall not be cause for rejection. The specimens shall not be cut < 25 mm from the coil edges of the test sheet. 3.1.2.2 Coated Base Metal. The mechanical properties of the coated material in the as delivered condition shall conform to the requirements specified in the applicable GMW or industry substrate standards. 3.1.3 Physical Requirements. Coating mass and finish quality shall conform to the requirements prescribed in Table 1.
Table 1: Preferred Coatings and Coating Mass Requirements Note 1, Note 2
50G50G 60G60G 70G70G 90G90G 45A45A 52A52A
Exposed Coating Designation E E E N/A E E
Semi-exposed Coating Designation Note 3^ Z Z Z Z N/A N/A
Unexposed Coating Designation U U U U U U
Minimum Average Coating Mass Each Side by Triple Spot Test (g/m^2 )
50 60 70 90 45 52
Maximum Average Coating Mass Each Side by Triple Spot Test (g/m^2 )
70 90 100 120 60 74
Minimum Coating Mass for any Individual Spot (g/m^2 )
43 50 60 75 40 45
Coating Thickness Each Side Note 1 Min/max (microns):
7.9/9.9 8.5/12.7 9.9/14.1 12.7/16.9 6.3/8.5 7.3/10.
Note 1 : Coating thicknesses are shown for reference only, not for conformance to specification requirements. Note 2 : Other coating masses may be used by exception. Refer to Deviations section. Note 3 : Semi-exposed designation is not applicable for GME. Note 4 : N/A = Not applicable
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GMW8 GM WORLDWIDE ENGINEERING STANDARDS
© Copyright 2008 General Motors Corporation All Rights Reserved
Page 4 of 9 February 2008
3.2.1.2.2 Fusion Welding Applications. Precoated flat products furnished to this specification shall be suitable for fusion welding as agreed upon by the supplier and purchaser and/or GMW14058. If necessary, special measures shall be taken. 3.2.1.3 Adhesive Compatibility. For bonded applications, the surfaces of the hot-dip zinc coated flat products furnished to this specification shall be capable of being adhered with the respective adhesives specified for the particular application. For GMNA, GMLAAM, and GMAP, the adhesive compatibility must meet the requirements of GM3624M. For GME, the steel approved to this specification shall be tested according to the test matrix in Appendix C. The only acceptable separation mode of the adhesive to the steel shall be cohesive within the adhesive layer. Adhesive separation of the adhesive layer to a test substrate shall be deemed unacceptable. 3.2.1.4 Zinc-Iron Alloy Coating Powdering. Zinc- Iron Alloy (galvannealed) coated sheet steel shall be tested for excessive powdering during forming according to GMB LTP.ME.339. 3.3 Requirements on other Stages during Life Cycle. 3.3.1 Chemical Requirements. Provisions shall be made to prevent the addition of such elements (see paragraph 5.2) from scrap or other materials used in the manufacturing process which would impair the recyclability of the finished components.
4 Manufacturing Process
Not applicable.
5 Rules and Regulations
5.1 All materials supplied to this standard must comply with the requirements of GMW3001, Rules and Regulations for Material Specifications. 5.1.1 Quality Requirements. The supplier shall have quality process control procedures compliant with ISO/TS 16949 or as required by GM Global Purchasing and Supply Chain (GPSC) demonstrating that the product will conform to all specification requirements. The data required to be submitted for this specification for each shipment will be determined by the regional manufacturing location. 5.2 All materials supplied to this standard must comply with the requirements of GMW3059, Restricted and Reportable Substances for Parts.
6 Approved Sources
Engineering qualifications of an approved source are required for this standard. Only sources listed in the GM Materials File (i.e., GM Supply Power) under this standard number have been qualified by engineering as meeting the requirements of this standard. For other GM locations, the responsible engineering group should be contacted to obtain the approved source in that individual country.
7 Notes
7.1 Glossary. Not applicable. 7.2 Acronyms, Abbreviations, and Symbols. ASTM ASTM, International CR Cold Rolled CTS Component Technical Specification EG Electrogalvanized EN European Norm GM General Motors GMAP General Motors Asia Pacific GMB GM Brazil GMDAT General Motors Daewoo Auto & Technology GME General Motors Europe GMLAAM General Motors Latin America, Africa, and Middle East GMNA General Motors North America GMW General Motors Worldwide GPSC Global Purchasing and Supply Chain HD Hot Dip (galvanized) HR Hot Rolled ISO International Organization of Standards JIS Japanese Industrial Standards MPa Mega Pascals MPS Manufacturing Engineering Metal Parts Specification SWE Secondary Work Embrittlement VDA German Association of the Automotive Industry (Verband der Automobilindrie)
8 Coding System
This standard shall be referenced in other documents, drawings, etc., as follows: Material per GMW The coding system for GMW sheet steel specifications on engineering part drawings shall use a nomenclature consisting of material, grade
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GM WORLDWIDE ENGINEERING STANDARDS GMW
© Copyright 2008 General Motors Corporation All Rights Reserved
February 2008 Page 5 of 9
and coating designation. The coding system for GMW sheet steel specifications on manufacturing engineering documents (i.e., GMNA Manufacturing Engineering Metal Parts Specification (MPS) Sheets) shall also consist of material, grade and coating designation, but with additional designations for type of sheet steel and formability grade for low carbon steel base metals, or type of sheet steel and minimum yield strength for high strength steel base metals. The designation for type of sheet metal used for base metal (i.e., CR for cold rolled, HR for hot rolled), formability grade for low carbon steel base metal or minimum yield strength for high strength steel base metal is contained in the applicable GMW or industry base metal material specification. The coating designation is defined in 1.1. 8.1 Example of Engineering Part Drawing Coding. GMWXM-ST-S-XXX-HD60G60G-U Where:
GMW = Validation Area (GM Worldwide
X = (^) Sequential Number
GMWX = Base Metal Specification
M =^ Material Type: Metals
ST =^ Category: Steel
S =^ SubCategory: Sheet
XXX =^ Steel Product Type, Grade
HD60G60G =^ Coating Designation
U Surface Quality
8.2 Example of Manufacturing Engineering Document Coding. GMWXM-ST-S-CRXXX-HD60G60G-U Where:
GMW = Validation Area (GM Worldwide X = (^) Sequential Number
GMWX = Base Metal Specification
M =^ Material Type: Metals
ST =^ Category: Steel
CRXXX =^ Steel Metal Type (CR) and Grade (XXX)
HD60G60G =^ Coating Designation
U =^ Surface Quality
9 Release and Revisions
9.1 Release. This specification was originated in June 1996 by the GM-NAO Sheet Metal Specialists Team and a team of GMIO Materials Engineering Experts. It was first approved by GM- NAO, Opel ITDC, GMB, Delta Motors, and Holden Ltd. in May 1998. It was first published in October
9.2 Revisions.
Rev Approval Date
Description (Organization)
C SEP 2007 Revisions to sections 1, 1.1, 1.2: cross-references, 2.1, 2.2, 2.3, 3.1.1.4, 3.1.2.1, 3.1.3 – Table 1, 3.1.3.3, 3.1.3.4, 3.1.4.1, 3.2.1.1, 3.2.1.2.2, 3.2.1.3, 5.3(added), 7 (added), Appendix A (deleted – phosphateability/paint appearance, added – Cross- Reference Table), Appendix B (added) Appendix C (added), Deviations - 3.1.2.1 (added), 3.1.3.1 Coating Mass, 3.2.1. (deleted).(Global Sheet Metal Specialists Team).
D FEB 2008 Publication Error, Appendix C updated. (Global Sheet Metal Specialists Team).
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GM WORLDWIDE ENGINEERING STANDARDS GMW
© Copyright 2008 General Motors Corporation All Rights Reserved
February 2008 Page 7 of 9
Appendix B
B1 Maximum Bend Test Radii for High Strength and Advanced High Strength Steels
Zinc Adhesion Testing shall be performed in accordance to ISO 7438.
Table B1: Grade (Coated to GMW8)
Grade (Coated to GMW8) Max. Test Radius, r
GMW3032M-ST-S HR550LA 2t
GMW3399M-ST-S CR450T/250Y DP 1t
GMW3399M-ST-S CR490T/290Y DP 1t
GMW3399M-ST-S CR590T/280Y DP 1t
GMW3399M-ST-S CR590T/340Y DP 1t
GMW3399M-ST-S CR590T/420Y DP 1t
GMW3399M-ST-S CR690T/550Y DP 2t
GMW3399M-ST-S CR780T/420Y DP 1t
GMW3399M-ST-S CR780T/500Y DP 2t
GMW3399M-ST-S CR980T/550Y DP 3t
GMW3399M-ST-S CR980T/650Y DP 4t
All other GMW3399 steels 1t
r
t
Figure B1: 90 Degree Bend Test Schematic
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Appendix C
C1: Adhesive Compatibility on New Substrates (GME)
X Minimal Test (to be tested generally)
V To be tested only on agreement
O To be tested only in case of need (adhesion requirements per GMW14706 not met)
Surface Quality
Adhesion Peel Test Shear Strength Test
(GMW14706) (ASTM D1876) (ISO 4587)
Adhesive
Temp [°C]
Time [minutes] Lubrication
before aging before aging before aging
170 20 X O X L 000 0726
190 60 X O X
170 20 X O X L 000 0728
190 60 X O X
170 20 X O - L 000 0780
190 60
Substrate shall be delivered with permitted lubricant (see Lubricants Table)
X O -
Surface Quality
GMW2 (Uncoated )*^ X
GMW11 EGN (ZnNi) X
GMW11 EGG (ELO) V
GMW8 HDG (HDG) X
GMW8 HDA (Galvannealed) X
GMW15056 (Precoated) X
GMW11 EGG (prephospated) X
Other not listed surfaces X
*To be tested with L 000 0058
Lubricants
B 440 0648 (3.0 g/m²)
Fuchs RP 4107 LV
B 040 1270
(3.0 g/m²)
Fuchs RP 4107
B 440 1271^ Fuchs^ PL 3802-39 S (3.0 g/m²) (^) Z&G PL 61
Spot Lubricant (3.0 g/m²)
Z&G KTL N 16
Hotmelt (1.7 g/m²)
Z&G Drylube E 1
Sealer & Adhesives
L 000 0726 Henkel/Teroson 3919 S X
L 000 0728 Dow Corning Betamate 1496 V X
L 000 0780 Henkel/Teroson Terostat 3233AA-25 X
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