1、WORLDWIDEENGINEERINGSTANDARDSMaterial Specification GMW2Low Carbon Sheet Steel Copyright 2012 General Motors Company All Rights ReservedOctober 2012 Originating Department: North American Engineering Standards Page 1 of 141 ScopeThis specification covers the requirements for low carbon continuous ca
2、st steel for exposed and unexposedapplications and is applicable to all low carbon steel sheet products and coated substrates. Continuously hot orcold rolled flat products shall be supplied as coils or sheet. Hot rolled flat products are usually supplied inthicknesses 1.75 mm. These flat products ar
3、e used for cold forming and for manufacturing of welded tubes.Cold rolled flat products with the appropriate surface type and surface finish are suitable for the application ofsurface coatings (metallic plating by melt dipping or thermal spray painting, electrolytic plating, organic coatingand/or ot
4、her coatings). This specification does not apply to steel for case hardening or strip applications.Additional requirements or agreements shall be specified by regional GM Automotive Operations (GM)business units, e.g., North America (GMNA), Europe (GME), Latin America, Africa, Middle East (GMLAAM),a
5、nd Asia Pacific (GMAP).1.1 Material Description. The material designation is defined by the General Motors Worldwide (GMW) basemetal specification number, steel product type and steel grade. The steel product type is designated by “CR“for cold rolled products, or “HR“ for hot rolled products. A nume
6、ral (1, 2, 3, etc.) will designate the steel gradeformability level. The steel grade will correspond to the chemical and mechanical requirements as shown inTable 1, Table 2, and Table 3. A third suffix (C) may be added after the steel grade to designate a low carbonsteelmaking practice. The finish t
7、ype, an alpha character, will designate the finish as E (exposed), or U(unexposed). In addition, products which are not coated shall have the word uncoated added to the call-outafter the steel type, but before the finish designation. The above descriptive items are used together to formthe coding sy
8、stem. Examples of the coding system for engineering part drawings and manufacturingengineering documents are shown in Section 8.1.2 Symbols. Not applicable.1.3 Typical Applications. Sheet metal parts consisting of low carbon steel products and coated low carbonsteel substrates.1.4 Remarks. Not appli
9、cable.2 ReferencesNote: Only the latest approved standards are applicable unless otherwise specified.2.1 External Standards/Specifications.ASTM A751 ASTM E112 EN 10002-1 EN 10247ASTM E45 DIN 1614-2 EN 10049 JIS Z 22012.2 GM Standards/Specifications.GM6180M GMW3224 GMW14704 GMW16066GMW8 GMW3335 GMW14
10、829 GMW16086GMW11 GMW14019 GMW14872 GMW16170GMW3011 GMW14699 GMW15200 GMW16549GMW3059 GMW14700 GMW15282 L 000 07262.3 Additional References.TMC003 Material Safety Data Sheet guidance documents (available at ).2.4 Cross-Reference of Replaced GM Regional Specifications. See Appendix A.Copyright Genera
11、l Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW2 Copyright 2012 General Motors Company All Rights ReservedOctober 2012 Page 2 of 143 RequirementsThe fol
12、lowing section defines specific requirements for material on delivery, processing, performance and otherstages during life cycle. Deviations required for individual GM business units are listed in the Deviation sectionat the end of this specification.For GME, the corresponding European Standards and
13、 EURONORMs shall apply in cases of dispute.3.1 Requirements on Delivery.3.1.1 Chemical Requirements.3.1.1.1 Base Metal. Base metal composition based on product (coil, or sheet/blank) analysis determined perASTM A751 shall conform to the requirements of Table 1. When end-product (coil/blank) test res
14、ults are notavailable, ladle analysis may be used. Chemical composition on the end product is the referee method.Table 1: Chemical Composition Note 1(Percent by Mass)Designation GMW2M-ST-S Note 2Element CR1, HR0 CR2, CR3, HR1, HR2,HR3 CR4 CR5Note 3Carbon Note 4 0.13 maximum 0.10 maximum 0.08 maximum
15、 0.02 maximumManganese 0.60 maximum 0.50 maximum 0.40 maximum 0.25 maximumPhosphorus 0.035 maximum 0.025 maximum 0.025 maximum 0.020 maximumSulfur 0.035 maximum 0.020 maximum 0.020 maximum 0.020 maximumAluminum Note 3, Note 5 Not Applicable 0.015 minimum 0.015 minimum 0.015 minimumNitrogen 0.008 max
16、imum Not Applicable Not Applicable Not ApplicableNote 1: Chemical Composition based on product (coil, or sheet/blank) analysis.Note 2: The letter C shall be added when a minimum Carbon content of 0.015% or 0.0003% (3 ppm) Boron is required (i.e., CR3C).Note 3: Titanium, Niobium and other alloys (e.g
17、., Boron) can be used in combination for fully stabilized/killed products. Stabilization alloysshall be reported.Note 4: Hot rolled grades with C% 0.5 mm the value for maximum yield stress is increased by20 MPa. For thicknesses 0.5 mm the value is increased by 40 MPa. For aluminized coatings, this v
18、alue is increased by 30 MPa.Note 5: When the specified nominal thickness is 0.5 mm the minimum value for elongation is reduced by 2 units. Forthickness 0.5 mm the minimum value is reduced by 4 units.Note 6: The values stated apply to product thickness 0.8 mm. When the specified nominal thickness is
19、0.6 mm and 1.4 mm and/or aluminized and galvanneal coatedproducts.Note 8: The value of r90 only applies to products of thickness 0.5 mm. When thickness is 2 mm and/or ZnNi, aluminized, andgalvanneal coated, the value for r90 is reduced by 0.2.Note 9: The n-values can be 0.01 lower for ZnNi, aluminiz
20、ed, and galvanneal coatings.Note 10: ZnNi, aluminized and galvanneal coated steels: total elongation shall be reduced by 2%.Note 11: CR5 shall not be specified with uncoated or electrogalvanized (EG) coatings.Copyright General Motors Company Provided by IHS under license with General Motors CompanyN
21、ot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW2 Copyright 2012 General Motors Company All Rights ReservedOctober 2012 Page 4 of 14Table 3: Hot Rolled Sheet and Hot Rolled Substrate, Mechanical Properties Note 1, Note 2Property
22、 Unit Designation GMW2M-ST-SHR0 HR1 HR2 HR3 Note 7Yield Strength Note 3, Note 6 MPa 240 to 350 210 to 320 180 to 290 180 to 260Tensile Strength MPa 310 minimum 310 to 430 270 to 400 270 to 380Total Elongation in 50 mm Note 5 % 26 minimum 30 minimum 34 minimum 38 minimumTotal Elongation in 80 mm Note
23、 3, Note 5 % 22 minimum 26 minimum 30 minimum 34 minimumTotal Elongation in 50 mm(JIS Z 2201 #5) Note 4, Note 5 % Not Required 33 minimum 39 minimum 42 minimumn value 0.12minimum0.14minimum0.16minimum0.18minimumNote 1: Additional demands can be specified by local units.Note 2: Parameters valid in th
24、e longitudinal and transverse test directions only.Note 3: The yield stress values shall apply for the 0.2% proof stress, Rp 0.2, if the yield stress cannot be easily recognized, the values shallbe the lower yield stress, ReL.Note 4: The values stated apply to product thicknesses of 2 mm to 3.2 mm.N
25、ote 5: When the specified nominal thickness is 3.2 mm minimum value for elongation is increased by 1 unit. Forthicknesses 6.3 mm the value is increased by 2 units, 1.6 mm is reduced by 1 unit.Note 6: Maximum yield strength shall be increased by 30 MPa for product thickness 2.0 mm and below.Note 7: T
26、otal Elongation in 50 mm and 80 mm reduced by 1 unit in transverse direction for hot dip coatings.3.1.3 Physical Requirements.3.1.3.1 Material Thickness and Tolerance. The detailed engineering part drawing/electronic math file willspecify the material thickness and tolerance. The tolerance requireme
27、nts for various thicknesses and strengthlevels are listed in GMW3224.3.1.3.2 Surface Requirements.3.1.3.2.1 Surface Condition. Specific requirements for the condition for each region are detailed in Deviationsection at the end of this document.3.1.3.2.2 Quality. The steel shall be free from surface
28、defects as negotiated between purchaser and supplier.For unexposed (U) surface, defects such as pores, slight indentations, small marks, minor scratches, andslight coloring, which do not affect formability or the application of surface coatings, are allowed. Exposed (E)surfaces shall be free of defe
29、cts which might affect the uniform appearance of a quality paint or an electrolyticcoating (elpo, electrodeposited primer, cathodic e-coat). Certain applications require that both surfaces of thesteel be of exposed (E) surface quality. A special requirement for temper rolling may be required and sha
30、ll bespecified with a (T) designation. Other surfaces shall conform at least to surface quality U. Detailedrequirements will be issued by the responsible formability analysis organization (e.g., GMNA ManufacturingEngineering Metal Parts Specification (MPS) sheet, GM responsible manufacturing or meta
31、llurgicalengineering document, etc.)3.1.3.2.3 Pre-Treatment/Paint Adhesion of Heat Treated Parts (Qualification Testing). For paintedapplications the surface shall be capable of achieving a high quality zinc phosphate conversion coatingaccording to GMW3011 (for crystal size and coating weight) and a
32、lso capable of meeting coating thicknessand coating weight requirements in GMW16170 for nano-ceramic pretreatment.After application of production representative primers and paints, parts shall meet the following requirements:adhesion of the E-coat shall fulfill the test requirements of the crosshatc
33、h test according to GMW14829(requirement: Rating 0) and the delamination test according to GMW14704 (Rating 0 or 1 after 48 hours testduration) for paint adhesion. For fully painted applications on exposed (E) surfaces, the material shall alsomeet the requirements of the stone chip resistance test a
34、ccording to GMW14700, method A (or B) andmethod C, with a minimum stone impact resistance rating of 8.Creep back resistance shall be inspected on e-coated samples for both zinc phosphate and nano-ceramicpretreatments. The samples shall be scribed per GMW15282 and tested according to GMW14872, EXT, A
35、ll,Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW2 Copyright 2012 General Motors Company All Rights ReservedOctober 2012 Page 5 of 144
36、salt spray per cycle, method 1/2/3, exposure C. For comparison, reference samples with HD60G60G orEG60G60G coatings shall be tested in parallel. The creep back shall be evaluated per GMW15282. The creepback resistance shall be comparable or better in comparison to the reference samples.3.1.3.2.4 Adh
37、esive Compatibility (Qualification Testing). Surfaces of pre-coated and uncoated flat productsand/or finished parts furnished to this specification shall be capable of being bonded with GM approvedadhesives when tested according to GMW16549. Testing to this specification will evaluate bondingcharact
38、eristics to the base metal and the strength of the bond between the coating and the base metal.An initial lap shear test, cold test and corrosion test shall be performed in the “under baked“ and “over baked“conditions. Results for lap shear strength shall be 16 MPa after initial testing and 12 MPa a
39、fter cold testing.The ultimate strength and separation mode according to GMW15200 shall be reported.3.1.3.2.5 Coating Adhesion Test. Refer to coating requirements in GMW8 for hot dipped zinc-based coatings,GMW11 for electrogalvanized coatings, and GMW16066 for aluminized coatings. Coating requiremen
40、tsinclude, but are not limited to coating composition, coating mass, and coating adhesion.3.1.3.3 Microstructure Requirements.3.1.3.3.1 Grain Size. Grain size shall be Number (No.) 6 and finer when tested to ASTM E112 and shall beconsistent throughout the thickness of the sheet.3.1.3.3.2 Inclusions.
41、 Two (2) optional methods for analysis are available. There shall be an agreement withthe local organization regarding which of the two following methods shall be performed.Method A: ASTM E45 Method D, Plate I-r, by analysis at 100 , inclusion content shall not exceed a rating of2.0 for thin and 2.0
42、 for heavy.Method B: EN 10247, inclusions shall not exceed size index 2.3.1.4 Additional Requirements.3.1.4.1 Marking. Unless otherwise agreed at the time of ordering, marking shall be carried out on theunexposed surface of full finish coils for outer panels and on the outer side of the coils for in
43、ner panels. Themarking shall be agreed upon between the supplier and purchaser. The ink used for marking shall be releasedby the purchaser.3.1.4.2 Other Requirements. Requirements such as tolerances on product shape and dimensions,inspections units, number of tests, sampling, test conditions, re-tes
44、ts, inspection documents, packing, andhandling of disputes shall be agreed upon between supplier and the local business unit.3.2 Processing Requirements.3.2.1 Additional Requirements.3.2.1.1 Welding. The steel products supplied to this standard shall be suitable for welding by the usual weldingmetho
45、ds.3.2.1.2 Weld Seams in Coils. If weld seams in cold rolled material are allowed by Global ManufacturingEngineering Department, the following restrictions have to be considered:For cold reduced coils, pickling weld seams from the manufacturing process of hot rolled coils is permissiblewithout restr
46、iction. Punch holes may be used for cold reduced coils to detect weld seams, but must be avoidedin stamped parts. For cold reduced coils with exposed (E) or semi-exposed (Z) surfaces, weld seams arepermissible, but must be indicated by perforation. For cold reduced coils with unexposed (U) surfaces,
47、 weldseams are not permissible unless special exceptions are made by the local organization. For hot rolled coils,weld seams are not permissible.3.2.1.3 Stretcher Strains. All exposed and semi-exposed products shall be free from stretcher strains for six(6) months. All unexposed products shall be fr
48、ee of stretcher strains as agreed upon between purchaser andsupplier.3.2.1.4 Secondary Work Embrittlement. Secondary Work Embrittlement (SWE) may occur in some interstitialfree flat steel products under very specific conditions. Secondary work embrittlement testing will be required forany steels tha
49、t have less than 0.015% carbon by mass. All material supplied to this specification shall bedetermined to be free of secondary work embrittlement per GMW16086 or as agreed upon between thepurchaser and supplier. Conformance to this requirement shall be verified at the time of approval and at thetime of the initial production shipment, unless otherwise required by the purchaser.Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for
