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GB/T 37778-2019 (GB/T37778-2019)

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GB/T 37778-2019: PDF in English (GBT 37778-2019)
GB/T 37778-2019
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 
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
GB/T 19805 Qualification test of welding operators
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.
5.2.2 Welding operators
Welding operators shall be trained in accordance with the relevant
requirements of GB/T 19805, and only after they have the corresponding ability
can they start operation. The welding operators holding permit shall be
evaluated regularly to ensure its validity.
5.2.3 Inspector
The inspectors include visual inspection and non-destructive testing personnel,
who shall understand laser beam welding technology and have the
qualifications specified in GB/T 9445 or have equivalent qualifications. If the
testing method exceeds the scope of GB/T 9445 or specified by equivalent
qualifications, a testing procedure equivalent to GB/T 9445 shall be developed.
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.
In order to ensure the accuracy of product assembly and meet the requirements
of laser beam welding, the tooling and fixture shall have high positioning
adjustment or other methods.
Pay attention to cleanliness during the whole process of assembly and welding
at the laser beam welding station.
The cutting of stainless steel uses dedicated stainless steel cutting and
polishing pads. In principle, the parts are cut by cold cutting. For parts where
cold cutting cannot be achieved, plasma cutting is used to cut and leave a
margin of 2 mm ~ 3 mm; then use stainless steel dedicated grinding tools are
used for grinding, until the size is guaranteed.
Confirm the product assembly quality. For lap welds, the workpieces shall be
closely attached; the assembly gap shall not be greater than 0.2 mm. It may
use feeler gauges and other tools for testing.
For butt and fillet welds, the gap is controlled according to the laser spot
diameter and welding procedure qualification results.
Prepare process documents to guide the operator in assembly and record the
results of assembly.
8.3.2 Welding control requirements
8.3.2.1 Welding sequence
Prepare laser beam welding sequence plan. The principle of welding sequence
formulation is to reduce welding distortion and improve production efficiency.
Each process of laser beam welding operation must strictly implement the
corresponding welding sequence plan.
The welding sequence plan shall at least include the following:
- Material information, including material name, code, material, plate
thickness, etc.
- Process division based on the production cycle.
- Laser beam welding seam's position number, the plate thickness
combination and welding parameters corresponding to this number are
pictorially shown in the corresponding position of the product.
- For the welding sequence of laser beam welded seam, the corresponding
program number shall be programmed by the automation equipment.
8.3.2.2 Workpiece assembly
For working conditions that cannot be assembled using tooling and fixtures,
laser beam tack welding can be used to assist in the assembly of parts. In
- Preparation of joints (such as shape and size);
- Joint assembly, fastening and tack welding;
- Set welding parameters according to WPS;
- In order to ensure the welding quality, a simplified working test piece shall
be used to confirm the state of the laser beam welding procedure
parameters. Refer to Appendix D for the test.
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.
The inspection record shall contain at least the following:
- Product drawing conformity inspection, including product basic size, shape
and position tolerance size.
- The visual inspection record of the laser beam welded seam.
- Record of laser beam welded seam's fusion state.
- Non-destructive testing report.
- Inspector’s signature.
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.
9.1.2 Smoothness inspection
For welded joints of dissimilar materials, the tensile strength shall generally not
be lower than the minimum value specified in the base metal standard of lower
strength.
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 minimum value
specified in the base metal standard before cold rolling.
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.
For plate butt joints of dissimilar (or heterogeneous) materials, two longitudinal
bending specimens (one forward bending and one back bending) can be used
instead of transverse bending specimens.
When there are no other requirements, the bending angle shall be 180°. The
diameter of the bending center is selected according to the relevant technical
conditions.
9.2.2.2 Qualified level
When there are no other requirements, the specimen shall not show any defects
with a length exceeding 3 mm in any direction during the bending process.
Defects that appear at the edge of the specimen that are not caused by welding
defects may be ignored in the evaluation.
9.2.3 Metallographic test
9.2.3.1 Method
The macroscopic metallographic test shall meet the requirements of GB/T
26955; observe and test with the naked eye or a low-power magnifying glass
(below 50x).
The macroscopic metallographic test may include the unaffected part of the
base metal. The microscopic metallographic test shall meet the requirements
of GB/T 26955.
For level B/BF welds, the inspection shall include macroscopic and microscopic
metallographic tests. The test results shall be accompanied by corresponding
metallographic photos.
For level C/CF welds, only the macroscopic metallographic test can be done.
The test results shall be accompanied by corresponding metallographic photos.
When laser beam welding is used for repair, the minimum distance between the
repaired weld and the center of its adjacent weld shall not be less than 2 mm.
When laser beam welding is used for repair, the number of repairs shall not
exceed 3.
When resistance spot welding repair involves appearance quality, the outer
surface can be padded with a copper plate, to ensure the flatness of the welding
area.
For arc welding repair, intermittent welding is generally used; however, plug
welding is used for locations where intermittent welding cannot be used.
When laser beam welding or arc welding is used to repair the weld, the length
of the weld is at least 20 mm longer than the defective weld, that is, at least 10
mm of the original weld must be covered at both ends of the repair weld.
When using resistance spot welding or plug welding to repair the weld, whether
a weld can replace the length of the laser weld is determined according to the
design requirements of the technical department. When using resistance spot
welding to repair the laser beam welded seam, in principle, the resistance
welding spot must not overlap with the laser beam welded seam. The spacing
of the solder joints may be adjusted according to the design strength
requirements. There shall be a solder joint in the middle of the defective weld;
there shall be a solder joint, each at both ends of the weld, that exceeds the
defect. That is, the arrangement of the solder joint shall exceed the scope of
the defective weld.
......
 
(Above excerpt was released on 2021-04-04, modified on 2021-06-07, translated/reviewed by: Wayne Zheng et al.)
Source: https://www.chinesestandard.net/PDF.aspx/GBT37778-2019