GB/T 37778-2019 PDF English
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Recommended process for laser beam welding on stainless steels
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GB/T 37778-2019: Recommended process for laser beam welding on stainless steels---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT37778-2019
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 25.160.10
J 33
Recommended process for laser beam welding on
stainless steels
Issued on. AUGUST 30, 2019
Implemented on. MARCH 01, 2020
Issued by. State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword... 3
1 Scope... 4
2 Normative references... 4
3 Terms and definitions... 5
4 Symbols... 6
5 General requirements... 7
6 Design requirements... 8
7 Quality requirements... 10
8 Welding procedure... 19
9 Inspection and test methods... 25
10 Repair of weld defects... 28
Appendix A (Informative) Typical joint design and recommended process
parameters of stainless steel welding... 30
Appendix B (Informative) Inspection test method... 31
Appendix C (Informative) Common defects in laser beam welding on stainless
steel and countermeasures... 36
Appendix D (Informative) Simplified work test piece... 37
Foreword
This standard was drafted in accordance with the rules established by GB/T
1.1-2009.
This standard was proposed by and shall be under the jurisdiction of the
National Welding Standardization Technical Committee (SAC/TC 55).
The main drafting organizations of this standard. CRRC Qingdao Sifang
Locomotive and Rolling Stock Co., Ltd., Baoji Petroleum Steel Pipe Co., Ltd.
(National Petroleum and Natural Gas Pipe Engineering Technology Research
Center), Guangzhou Special Pressure Equipment Testing and Research
Institute, Harbin Welding Research Institute Co., Ltd., Fujian Provincial
Industrial Equipment Installation Co., Ltd.
The main drafters of this standard. Han Xiaohui, Yang Zhongwen, Li Maodong,
Zhang Zhiyi, Lu Ansong, Ma Yin, Xu Shidong, Su Jinhua, Lei Zhen, Zhu
Shaohua, Jiang Yuan.
Recommended process for laser beam welding on
stainless steels
1 Scope
This standard specifies the recommended process specifications, including
general requirements, design requirements, quality requirements, welding
procedure, inspection and test methods, weld defect reassembly, for laser
beam welding on stainless steels.
This standard applies to laser beam welding on stainless steel which has a
thickness of 0.6 mm ~ 5 mm.
2 Normative references
The following documents are essential to the application of this document. For
the dated documents, only the versions with the dates indicated are applicable
to this document; for the undated documents, only the latest version (including
all the amendments) are applicable to this standard.
GB/T 2651 Tensile test method on welded joints
GB/T 2653 Bend test methods on welded joints
GB/T 3323 Radiographic examination of fusion welded joints in metallic
materials
GB/T 3375 Welding terminology
GB 7247.1 Safety of laser products - Part 1.Equipment classification and
requirements
GB/T 9445 Non-destructive testing - Qualification and certification of NDT
personnel
GB/T 18490.1 Safety of machinery - Laser processing machines - Part 1.
General safety requirement
GB/T 18851.1 Non-destructive testing - Penetrant testing - Part 1.General
principles
3 Terms and definitions
The terms and definitions as defined in GB/T 3375, GB/T 19866, GB/T 19867.4
as well as the following terms and definitions apply to this document.
3.1
Appearance quality
The appearance effects of the face of weld and root surface, such as the
quality requirements for spatter, penetrated fusion, smoothness, point
imperfections and scratches and other minor defects.
3.2
Smoothness
An indicator for evaluating the degree of unevenness on the back of welds
of incomplete penetration lap joints.
3.3
Point imperfection
Non-penetrated point-like protrusions or depressions formed by local
excessive heat of welding area.
3.4
Scratch
Marks on a smooth material surface due to mechanical effects.
4 Symbols
The following symbols apply to this document.
t - Thickness of base metal;
ΔL - The distance between two imperfections (pores, shrinkage);
s - Depth of fusion;
5 General requirements
5.1 General
For laser beam welding on stainless steel, in addition to meeting the
requirements of this standard, the welding operation shall also comply with the
requirements of relevant product standards (such as GB/T 25343.1). Laser
beam safety shall comply with the requirements of GB 7247.1 and GB/T
18490.1 and related technical documents.
5.2 Personnel qualifications
5.2.1 Product assembler
Product assemblers shall understand the laser beam welding technology and
pass pre-work process training before starting operations.
5.3 Process equipment
5.3.1 Laser beam welding equipment
Laser beam welding equipment shall be regularly inspected to be in normal
working condition.
5.3.2 Tooling and fixture
The tooling and fixture shall use the materials, which have good heat dissipation
conditions and can form a good protection for stainless steel, such as aluminum
alloy or copper alloy.
5.4 Workpiece
5.4.1 Materials
Stainless steel raw materials shall meet the design requirements; their
performance indicators shall meet the requirements of GB/T 33239; it can meet
the high-precision forming requirements of laser beam welded parts.
5.4.2 Processing requirements
The parts can be processed by punching, laser cutting, stamping or other
suitable methods. The processed parts shall be removed of residual burrs at
the cutting part.
5.5 Environmental requirements
The welding site shall be kept clean and have necessary isolation measures.
6 Design requirements
6.1 General principles
For the design documents and drawings of the product, it shall be based on the
product usage to determine the design requirements, such as mechanical
properties, structural form, appearance quality, etc.
6.4 Quality level requirements for imperfections
According to the different mechanical properties and appearance quality
requirements of the weld, the imperfections are divided into six levels. level B,
level BF, level C, level CF, level D, level DF, based on severe, medium, ordinary.
See Table 1 for details.
6.5 Weld inspection level requirements
The inspection level of each joint is determined according to the weld quality
level of the joint, as detailed in Table 2.
6.6 Mechanical performance requirements of welded joints
6.6.1 Tensile strength of butt joints
The tensile strength of the butt joint shall not exceed the lower limit of the tensile
strength required by the standard of base metals of lower strength grade; if the
strength of the base metal is obtained through the cold rolling process, the
tensile strength of the joint shall not be lower than the lower limit of the tensile
strength of the base metal before cold rolling.
6.6.2 Tensile shear strength of lap joint
The tensile shear force when the weld length of the lap joint is 30 mm may, if
there is no special requirement, be carried out according to the requirements of
Table 3.
7 Quality requirements
7.1 Limit value of imperfection size
7.1.1 Butt joint
7.1.1.1 Undercut
7.1.1.4 Misalignment
The misalignment of the welded joint (Figure 4) shall meet the requirements of
Table 7.
7.1.3 T-joint
For different levels of T-joint weld offset, the specified joint axis limits (see
Figure 9) are controlled in accordance with Table 12.
7.2 Acceptance criteria for weld imperfection
7.2.1 Cracks
In all types of welded joints, all cracks except for microcracks (the length and
width of the crack are less than 1 mm) are not allowed to exist.
Crater cracks are not allowed, for levels B/BF, C/CF welded joints; local crater
cracks are allowed, for level D/DF welded joints (the crack length and width are
both less than 1 mm).
7.2.7 Other imperfections
7.2.7.1 Spatter
Whether the spatter (Figure 15) is allowed or not, for the levels B, C, and D, it
shall be implemented according to product technical conditions or through
negotiation between the two parties. For levels BF, CF, DF welds, the spatter is
not allowed on the face of weld, however, it is allowed on the root surface.
7.2.7.2 Melt through
The laser beam penetrates the opposite side of the welding surface to form a
perforation. Whether the welds of levels B, C, D are allowed or not depends on
the specific application conditions; it is not allowed for the welds of levels BF,
CF, DF.
7.2.7.3 Point imperfections
Whether point imperfections are allowed for welds of levels B, C, D depends on
the specific application conditions; welds of levels BF, CF, DF do not allow
protrusion, however, it allows dents;
7.2.7.4 Smoothness
The smoothness is the height difference H between the base metal of the back
of the weld and the center of the back of the weld at a distance of 15 mm from
the center of the weld (Figure 16).
8 Welding procedure
8.1 Welding procedure qualification
8.1.1 General requirements
When performing process qualification, the general butt weld test piece and T-
joint test piece shall be assessed according to the requirements of GB/T 29710;
the lap weld test piece shall be prepared according to the requirements of 8.1.2.
8.1.2 Test piece for lap weld
8.1.2.2 Shape and size of test piece for lap penetration weld
The lap penetration weld (double layer) is as shown in Figure 18.
Lap penetration welds include the following types.
8.1.3 Test and inspection
Various test pieces shall be tested and inspected according to Table 16.See
Chapter 9 for specific methods.
8.1.4 Conformity assessment
All test and inspection items shall be judged according to Chapter 9; they shall
be qualified if they meet the restrictive requirements. In case of unqualified
items, it is allowed to double the quantity of test pieces for retest. If the
additional test piece still does not meet the relevant requirements, the welding
procedure qualification is unqualified.
8.3 Welding
8.3.1 Assembly before welding
The grinding wheel blades, chisels, pressing devices, hammers and other craft
tools are all dedicated for stainless steel, to avoid direct contact between carbon
steel and stainless steel.
8.3.2 Welding control requirements
8.3.3.2 During welding
During the welding procedure, the welding sequence and welding procedure
parameters shall be continuously monitored or regularly checked.
8.3.3.3 After welding
After the welding is completed, it shall carry out the appearance quality
inspection of the welded joints and the conformity inspection of the product
drawings; meanwhile, retain the inspection records.
9 Inspection and test methods
9.1 Inspection method
9.1.1 Visual test (VT)
Visual test of appearance shall be carried out in accordance with GB/T 32259.
Check the weld surface for defects such as cracks, surface grooves, incomplete
penetration; check the misalignment of the joint and the amount of surface
depression, etc.; judge and record in accordance with the provisions of Chapter
7.
9.1.3 Non-destructive testing
9.1.3.1 Penetration testing (PT)
Penetration testing is carried out in accordance with GB/T 18851.1; the
acceptance level shall meet the requirements of GB/T 26953 or relevant
documents.
9.1.3.2 Radiographic testing (RT)
Radiographic testing is carried out in accordance with GB/T 3323.
9.2 Test method
9.2.1 Transverse tensile test
9.2.1.1 Method
The transverse tensile test shall be carried out at room temperature (or other
specified temperature). The specimens and test methods for transverse tension
of butt joints shall comply with the requirements of GB/T 2651.
9.2.1.2 Qualified level
Unless otherwise specified before the test, the tensile strength of the specimen
shall generally not be lower than the minimum value specified in the base metal
standard.
9.2.2 Bend test
9.2.2.1 Method
The bending specimen and test of the butt joint shall meet the requirements of
GB/T 2653.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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