GB/T 5779.1-2000 Fasteners Surface Defects Bolts, Screws and Studs General Requirements
Some standard content:
GB/T 5779. 1--2000
This standard is equivalent to the international standard ISO6157-1:1988 "Surface defects of fasteners Part 1: General requirements for bolts, screws and studs".
This standard is a revision of GB/T5779.1-1986, with the following major revisions: a) Adjustment of the allowable limit of "forging burst" (Article 3.1.3) b) Comprehensive provisions of the inspection and determination procedures and sampling plans for surface defects (Chapter 4 and Appendix A). This standard replaces GB/T5779.1-1986 from the date of implementation. Appendix A of this standard is the appendix to the standard.
This standard was proposed by the State Machinery Industry Bureau. This standard is under the jurisdiction of the National Technical Committee for Standardization of Fasteners. This standard was drafted by the Mechanical Science Research Institute. This standard is interpreted by the Secretariat of the National Technical Committee for Standardization of Fasteners. 369
GB/T5779.1-—2000
ISOForeword
ISO (International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The development of international standards is usually carried out through ISO's various technical committees. Each member body can also participate in the committee if it is interested in the project carried out by a technical committee. Governmental and non-governmental international organizations related to ISO can also participate in this work. ISO has close ties with the International Electrotechnical Commission (IEC) in electrotechnical standardization. The draft international standards adopted by the technical committee are distributed to all member bodies for voting. The formal publication of international standards requires at least 75% of the member bodies to vote in favor.
International Standard ISO6157-1 was developed by ISO/TC2 Fastener Technical Committee. Users must note that all international standards are revised from time to time, and any other international standards cited here should be confirmed as the latest version unless otherwise stated.
1 Scope
National Standard of the People's Republic of China
Surface discontinuities of fasteners
Bolts, screws and studs
General requirements
Fasteners-Surface discontinuities-Bolts, screws and studs for general requirementsGB/T 5779. 1-2000
idt ISO 6157-1:1988
Replaces GB/T5779.11986
1.1 The limits specified in this standard apply to various surface discontinuities of bolts, screws and studs for general requirements. Applicable bolts, screws and studs:
Nominal thread diameter equal to or greater than 5mm;
Product grade A and B;
Property grade equal to or less than 10.9, except where otherwise specified in the product standard or special agreement between the supplier and the buyer. 1.2 The limits of surface defects of bolts, screws and studs for special requirements (such as automated assembly) are specified in GB/T5779.3. When the engineering and technical conditions of use require more stringent control of the surface defects of bolts, screws and studs, the applicable limits should be specified in the relevant product specifications or by the user in the inquiry and order. 1.3 Even if the surface defects reach the allowable limits specified in Chapter 3, the mechanical and working properties of the product shall still meet the minimum requirements of GB/T3098.1. In addition, the dimensional requirements of the corresponding product standards shall also be met. Notes
1 The figures in Chapter 3 are examples only and are also applicable to other types of bolts, screws and studs. 2 For the sake of clarity, some surface defects are exaggerated in the figures. 2 Referenced standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T90-1985 Fasteners acceptance inspection, marking and packaging (eqv3269:1984) GB/T1031-1995 Surface roughness parameters and their values (negISO468:1982) GB/T2828-1987 Sampling procedures and sampling tables for batch inspection (applicable to inspection of continuous batches) GB/T3098.1-2000 Mechanical properties of fasteners Bolts, screws and studs (idtISO898-1:1999) GB/T5779.3-2000 Surface defects of fasteners Special requirements for bolts, screws and studs (idtISO6157-3:1988) GB/T15239-1994 Sampling procedures and sampling tables for isolated batch inspection 3 Types, causes, appearance characteristics and limits of surface defects 3.1 Cracks
A crack is a clear (crystalline) fracture along the metal grain boundary or across the grain, and may contain inclusions of foreign elements. Cracks are usually caused by excessive stress in the metal during forging or other forming processes or heat treatment, and may also exist in the raw materials. When the workpiece is heated again, the cracks usually change color due to the flaking of the oxide scale. Approved by the State Administration of Quality and Technical Supervision on September 26, 2000, implemented on February 1, 2001
3.1.1 Quench cracks
GB/T 5779. 1—2000
Quench cracks may occur during heat treatment due to excessive thermal stress and strain. Quenching cracks are usually irregular and intersecting, and appear in irregular directions on the surface of fasteners. Annular and adjacent head cracks at fillets. Root-carrying quenching cracks. Head corner quenching cracks. Tooth bottom cracks. Horizontal quenching cracks. Longitudinal cracks. Radially extending cracks into fillets. Continuous cracks. Any depth, length or position of cracks are not allowed. 3.1.2 Forging cracks cracks
GB/T5779.1—2000
Forging cracks may occur during the cutting or forging process and are located on the top surface of the bolt and screw head, as well as the raised part of the recessed head.
Detection
The length of the forging cracks! ：
Depth or width of forging cracks b;
b≤0.04d;
Nominal thread diameter
Forging brusts
Forging brusts may occur during the forging process, such as on the diagonal of the hexagonal head of bolts and screws, or on the flange surface or the threshold of round head products, or on the raised part of the head of the recess
Forging brusts
Forging brusts
Plating wall condensation
Hexagonal head and hexagonal flange bolts and screws: Forging brusts on the flange surface of hexagonal flange bolts and screws should not extend into the top circle (chamfered circle) of the top surface of the head or the bearing surface under the head. Forging brusts on the diagonal should not reduce the diagonal width to less than the specified minimum size. The width of the forging brusts on the raised part of the head of the bolt and screw recess should not exceed 0.06d or the depth should not be lower than the recess part. The width of forging cracks on the flange surface and round head circumference of round head bolts and screws and hexagonal flange bolts shall not exceed the following limits: ≤0.08d (or d) (when there is only one forging crack); ≤0.04d. or ds) (when there are two or more forging cracks, one of them is allowed to be up to 0.08d. or). Nominal thread diameter d --- head or flange diameter d head diameter 373
3.1.4 Shear bursts
GB/T 5779.1-2000
Shear bursts may occur during the forging process, such as on the circumference of the round head or flange surface of round head or flange surface products, usually at about 45° to the product axis
Shear bursts may also occur on the opposite side plane of hexagonal head products
- Shear burst
Shear burst
Hexagonal head and hexagonal flange bolts and screws: The shear bursts on the flange surface of hexagonal flange bolts and screws should not extend to the top circle (chamfered circle) of the top surface of the head or the bearing surface under the head. The diagonal shear bursts should not reduce the diagonal width to less than the specified minimum size. The width of the shear burst of the raised part of the head of the bolt and screw cavity shall not exceed 0.06d or the depth shall not be lower than the cavity part. Round head bolts and screws and hexagonal flange bolts: The width of the shear burst on the flange surface and round head circumference of the bolt and screw shall not exceed the following limits: ≤0.08d (or d) (when there is only one shear burst): ≤0.04d. (or dk) (when there are two or more shear bursts, one of them is allowed to be 0.08d. or ds). Thread nominal diameter; d—head or flange diameter; d head diameter GB/T 5779.1—2000
3.2 Cracks and streaks in raw materials Rowmaterial seams and laps Cracks or streaks in raw materials are usually defects of a thin straight line or smooth curve extending longitudinally along the thread, polished rod or head. Cause
Cracks and streaks are usually inherent defects in the raw materials used to manufacture fasteners, usually longitudinal
extending straight lines or smooth curves
double lines or contention marks, the passband is a longitudinal
extending straight line or smooth curve
The depth of the crack or streak:
0.03dt.
If the crack or streak extends to the head, it shall not exceed the permissible limits of width and depth specified for forging burst (Article 3.1.3). d-Nominal diameter of thread
3.3 Voids
GB/T 5779. 1--2000
A dent is a shallow pit or depression on the surface of a bolt or screw due to incomplete metal filling during forging or upsetting. Cause
A dent is a mark or impression caused by chips or shear burrs or rust layer of raw materials, which cannot be eliminated during the forging or upsetting process.
Depth of dent h:
h≤0.02d (maximum value is 0.25mm).
Area of dent:
The sum of the dent areas on the bearing surface shall not exceed 10% of the total area of the bearing surface. Thread Nominal Diameter
3.4 Folds
Folds are metal folds that appear on the surface of fasteners during the forging process. 376
3.5 Cut marks
GB/T 5779. 12000
- Wrinkles caused by displacement of materials
During the impact process of forging, due to insufficient volume and shape, typical wrinkles are allowed. Wrinkles are allowed at the junction of flange and plate. Wrinkles are allowed at the outer corners.
Wrinkles are allowed at the end surface
Chain marks are allowed at the outer corners
Wrinkles are not allowed at the inner corners
Wrinkles are not allowed at the inner corners located at or below the bearing surface, except for those specially allowed in the above diagrams or product standards. Wrinkles are allowed at the outer corners.
Tool marks
Cut marks are shallow grooves in the longitudinal or circumferential direction. Causes
Cut marks are caused by the movement of the manufacturing tool beyond the surface of the bolt or screwbzxZ.net
Cut marks caused by the trimming process are allowed.
On the polished rod, fillet or bearing surface, the surface roughness of the cut caused by processing shall not exceed Rα=~3.2μm (according to GB/T1031)
3.6 Damage Damages
GB/T5779.1--2000
Damage refers to the scratches on any surface of the bolt or screw. Damage, such as depressions, abrasions, notches and gouges, is caused by external influences during the manufacturing and transportation of the bolt or screw. There is no accurate geometric shape, position or direction, and it is impossible to identify the factors of external influence. The above damage shall not be rejected unless it can be proved that the function or usability is impaired. Depressions, abrasions, notches and gouges located in the first three threads shall not affect the passing of the thread gauge. The torque when tightening shall not be greater than 0.001d3N
" Thread nominal diameter
Inspection and judgment procedures
Acceptance inspection procedures are shown in GB/T 90. If the surface coating or plating affects the identification of surface defects, it should be removed before inspection. Note: GB/T90 will be deleted accordingly when it is revised to avoid repetition. 4.1 Rules
The manufacturer has the right to adopt any inspection procedure, but must ensure that the product complies with the provisions of this standard. The purchaser may adopt the acceptance inspection procedure specified in this article to determine whether a batch of fastener products is accepted or rejected. This procedure is also applicable to arbitration inspections in case of disputes, unless the supplier and the purchaser specify other acceptance procedures agreed upon in the order. 4.2 Non-destructive inspection
According to the provisions of Table A1 in Appendix A (Appendix to the standard), samples are randomly selected from the acceptance batch and subjected to visual inspection or other non-destructive inspection, such as magnetic technology or eddy current. If it is found that the defective samples do not exceed the allowable limit, the batch of products is accepted (see also Article 4.4) ; If the number of defective samples is found to exceed the allowable limit, these unqualified products shall be treated as a batch and further inspected according to the procedure of Article 4.3. 4.3 Destructive inspection
If unqualified products are found according to the procedure of Article 4.2, the products with the most serious defects shall be composed of the second sample according to the provisions of Table A2 in Appendix A, and a section perpendicular to the defect shall be taken at the maximum depth of the defect for inspection. 4.4 Determination
If quenching cracks are found in any part or wrinkles on the inner corners or wrinkles below the bearing surface and beyond the "three-leaf" shape on non-circular shoulder fasteners during visual inspection, the batch of products shall be rejected. If forging cracks, bursts, cracks and streaks, dents, cuts or damage exceeding the specified allowable limits are found during destructive inspection, the batch of products shall be rejected.
GB/T 5779. 1-2000
Appendix A
(Subject Appendix)
Sampling Plan for Surface Defects
Sampling for surface defects shall be based on the sample sizes given in Table A1 and follow the rules and procedures given in Chapter 4. Table A1
Sample sizes for visual inspection and non-destructive inspectionBatch1
N≤1200
1 201≤N≤10 000
10 001≤N≤35 000
35001≤N≤150.000
Note: Sample size is based on the inspection level S-4 specified in Table 10 of GB/T 15239. 1) Batch is the number of products of the same type, specification and performance level submitted for acceptance at the same time. Table A2
Second sample size for crack inspection
Number of defective products in the sample
51AN80
Note: The second sample size is based on the general inspection level 1 specified in Tables 2 and 3 of GB/T2828. Sample size
Second sample size12000
- Wrinkles caused by displacement of materials
During one impact of forging, due to insufficient volume and shape, typical wrinkles are allowed.
Wrinkles are allowed at the junction of flange and plate. Wrinkles are allowed at the outer corners.
Wrinkles are allowed at the end surface.
Chain marks are allowed at the outer corners.
Wrinkles are not allowed at the inner corners.
Wrinkles are not allowed at the inner corners located at or below the bearing surface, except for those specially allowed in the above diagrams or product standards. Wrinkles are allowed at the outer corners.
Tool marks
Cut marks are shallow grooves in the longitudinal or circumferential direction. Causes
Cut marks are caused by the movement of the manufacturing tool beyond the surface of the bolt or screw
Cut marks caused by the trimming process are allowed.
On the polished rod, fillet or bearing surface, the surface roughness of the cut caused by processing shall not exceed Rα=~3.2μm (according to GB/T1031)
3.6 Damage Damages
GB/T5779.1--2000
Damage refers to the scratches on any surface of the bolt or screw. Damage, such as depressions, abrasions, notches and gouges, is caused by external influences during the manufacturing and transportation of the bolt or screw. There is no accurate geometric shape, position or direction, and it is impossible to identify the factors of external influence. The above damage shall not be rejected unless it can be proved that the function or usability is impaired. Depressions, abrasions, notches and gouges located in the first three threads shall not affect the passing of the thread gauge. The torque when tightening shall not be greater than 0.001d3N
" Thread nominal diameter
Inspection and judgment procedures
Acceptance inspection procedures are shown in GB/T 90. If the surface coating or plating affects the identification of surface defects, it should be removed before inspection. Note: GB/T90 will be deleted accordingly when it is revised to avoid repetition. 4.1 Rules
The manufacturer has the right to adopt any inspection procedure, but must ensure that the product complies with the provisions of this standard. The purchaser may adopt the acceptance inspection procedure specified in this article to determine whether a batch of fastener products is accepted or rejected. This procedure is also applicable to arbitration inspections in case of disputes, unless the supplier and the purchaser specify other acceptance procedures agreed upon in the order. 4.2 Non-destructive inspection
According to the provisions of Table A1 in Appendix A (Appendix to the standard), samples are randomly selected from the acceptance batch and subjected to visual inspection or other non-destructive inspection, such as magnetic technology or eddy current. If it is found that the defective samples do not exceed the allowable limit, the batch of products is accepted (see also Article 4.4) ; If the number of defective samples is found to exceed the allowable limit, these unqualified products shall be treated as a batch and further inspected according to the procedure of Article 4.3. 4.3 Destructive inspection
If unqualified products are found according to the procedure of Article 4.2, the products with the most serious defects shall be composed of the second sample according to the provisions of Table A2 in Appendix A, and a section perpendicular to the defect shall be taken at the maximum depth of the defect for inspection. 4.4 Determination
If quenching cracks are found in any part or wrinkles on the inner corners or wrinkles below the bearing surface and beyond the "three-leaf" shape on non-circular shoulder fasteners during visual inspection, the batch of products shall be rejected. If forging cracks, bursts, cracks and streaks, dents, cuts or damage exceeding the specified allowable limits are found during destructive inspection, the batch of products shall be rejected.
GB/T 5779. 1-2000
Appendix A
(Subject Appendix)
Sampling Plan for Surface Defects
Sampling for surface defects shall be based on the sample sizes given in Table A1 and follow the rules and procedures given in Chapter 4. Table A1
Sample sizes for visual inspection and non-destructive inspectionBatch1
N≤1200
1 201≤N≤10 000
10 001≤N≤35 000
35001≤N≤150.000
Note: Sample size is based on the inspection level S-4 specified in Table 10 of GB/T 15239. 1) Batch is the number of products of the same type, specification and performance level submitted for acceptance at the same time. Table A2
Second sample size for crack inspection
Number of defective products in the sample
51AN80
Note: The second sample size is based on the general inspection level 1 specified in Tables 2 and 3 of GB/T2828. Sample size
Second sample size12000
- Wrinkles caused by displacement of materials
During one impact of forging, due to insufficient volume and shape, typical wrinkles are allowed.
Wrinkles are allowed at the junction of flange and plate. Wrinkles are allowed at the outer corners.
Wrinkles are allowed at the end surface.
Chain marks are allowed at the outer corners.
Wrinkles are not allowed at the inner corners.
Wrinkles are not allowed at the inner corners located at or below the bearing surface, except for those specially allowed in the above diagrams or product standards. Wrinkles are allowed at the outer corners.
Tool marks
Cut marks are shallow grooves in the longitudinal or circumferential direction. Causes
Cut marks are caused by the movement of the manufacturing tool beyond the surface of the bolt or screw
Cut marks caused by the trimming process are allowed.
On the polished rod, fillet or bearing surface, the surface roughness of the cut caused by processing shall not exceed Rα=~3.2μm (according to GB/T1031)
3.6 Damage Damages
GB/T5779.1--2000
Damage refers to the scratches on any surface of the bolt or screw. Damage, such as depressions, abrasions, notches and gouges, is caused by external influences during the manufacturing and transportation of the bolt or screw. There is no accurate geometric shape, position or direction, and it is impossible to identify the factors of external influence. The above damage shall not be rejected unless it can be proved that the function or usability is impaired. Depressions, abrasions, notches and gouges located in the first three threads shall not affect the passing of the thread gauge. The torque when tightening shall not be greater than 0.001d3N
" Thread nominal diameter
Inspection and judgment procedures
Acceptance inspection procedures are shown in GB/T 90. If the surface coating or plating affects the identification of surface defects, it should be removed before inspection. Note: GB/T90 will be deleted accordingly when it is revised to avoid repetition. 4.1 Rules
The manufacturer has the right to adopt any inspection procedure, but must ensure that the product complies with the provisions of this standard. The purchaser may adopt the acceptance inspection procedure specified in this article to determine whether a batch of fastener products is accepted or rejected. This procedure is also applicable to arbitration inspections in case of disputes, unless the supplier and the purchaser specify other acceptance procedures agreed upon in the order. 4.2 Non-destructive inspection
According to the provisions of Table A1 in Appendix A (Appendix to the standard), samples are randomly selected from the acceptance batch and subjected to visual inspection or other non-destructive inspection, such as magnetic technology or eddy current. If it is found that the defective samples do not exceed the allowable limit, the batch of products is accepted (see also Article 4.4) ; If the number of defective samples is found to exceed the allowable limit, these unqualified products shall be treated as a batch and further inspected according to the procedure of Article 4.3. 4.3 Destructive inspection
If unqualified products are found according to the procedure of Article 4.2, the products with the most serious defects shall be composed of the second sample according to the provisions of Table A2 in Appendix A, and a section perpendicular to the defect shall be taken at the maximum depth of the defect for inspection. 4.4 Determination
If quenching cracks are found in any part or wrinkles on the inner corners or wrinkles below the bearing surface and beyond the "three-leaf" shape on non-circular shoulder fasteners during visual inspection, the batch of products shall be rejected. If forging cracks, bursts, cracks and streaks, dents, cuts or damage exceeding the specified allowable limits are found during destructive inspection, the batch of products shall be rejected.
GB/T 5779. 1-2000
Appendix A
(Subject Appendix)
Sampling Plan for Surface Defects
Sampling for surface defects shall be based on the sample sizes given in Table A1 and follow the rules and procedures given in Chapter 4. Table A1
Sample sizes for visual inspection and non-destructive inspectionBatch1
N≤1200
1 201≤N≤10 000
10 001≤N≤35 000
35001≤N≤150.000
Note: Sample size is based on the inspection level S-4 specified in Table 10 of GB/T 15239. 1) Batch is the number of products of the same type, specification and performance level submitted for acceptance at the same time. Table A2
Second sample size for crack inspection
Number of defective products in the sample
51AN80
Note: The second sample size is based on the general inspection level 1 specified in Tables 2 and 3 of GB/T2828. Sample size
Second sample size
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