Some standard content:
GB/T 3098. 3-2000
This standard is equivalent to the international standard ISO898-5:1998 "Mechanical properties of fasteners made of carbon steel and alloy steel Part 5: Set screws and similar threaded fasteners not subject to tensile stress". The general title of GB/T3098 is "Mechanical properties of fasteners", which includes the following parts: - GB/T 3098.1—2000
GB/T 3098.2-2000
GB/T 3098.3—2000
GB/T 3098.4——2000
GB/T 3098.5-—2000
GB/T 3098.6-—2000
GB/T 3098.7--2000
- GB/T 3098.8--1992
GB/T 3098.9—1993
GB/T 3098.10
GB/T 3098. 11-
Bolts, screws and studs
Mechanical properties of fasteners
Mechanical properties of fasteners
Mechanical properties of fasteners
Mechanical properties of fasteners
Mechanical properties of fasteners
Mechanical properties of fasteners
Mechanical properties of fasteners
Mechanical properties of fasteners
Mechanical properties of fasteners
Mechanical properties of fasteners
GB/T 3098. 12---1996
GB/T 3098.13—1996
Coarse pitch thread
Set screws
Fine pitch thread for nuts
Self-tapping screws
Stainless steel bolts, screws and studs
Self-extruding screws
Heat-resistant threaded connections
Effective torque steel hexagonal locking nuts
Bolts, screws, studs and nuts made of non-ferrous metalsSelf-drilling and self-tapping screws
Mechanical properties of fasteners
Mechanical properties of fasteners
1~10 mm
-GB/T 3098.14—2000
Mechanical properties of fasteners
-GB/T3098.15--2000
Mechanical properties of fasteners
Nut cone guaranteed load test
Torque test and breaking torque of bolts and screws Nominal diameter Nut expansion test
Stainless steel nuts
GB/T3098.16—2000 Mechanical properties of fasteners Stainless steel set screws
Parallel bearing surface method
GB/T3098.17—2000 Mechanical properties of fasteners Inspection of hydrogen embrittlement Preload test
This standard does not adopt ISO898-5 Appendix A, and its content has been listed in the referenced standards (Chapter 2). This standard is a revision of GB/T3098.3—1982, with the following major changes: a) Only mechanical properties tested under ambient temperature of 10~35C are specified. At higher or lower temperatures, its mechanical and physical properties may be different (Chapter 1);
b) The specified thread nominal diameter is 1.6 to 24 mm (Chapter 1); c) The adjustment part guarantees the torque value (Table 5). This standard replaces GB/T3098.3--1982 from the date of implementation. This standard is proposed by the State Machinery Industry Bureau. This standard is under the jurisdiction of the National Technical Committee for Standardization of Fasteners. This standard is under the responsibility of the Mechanical Science Research Institute, and the Shanghai Fastener and Welding Material Technology Research Institute and the Wuhan Automobile Standard Parts Research Institute participated in the drafting.
This standard is interpreted by the Secretariat of the National Technical Committee for Standardization of Fasteners. 99
GB/T3098.3-2000
ISO Foreword
ISO (International Organization for Standardization) is a worldwide joint organization of national standard bodies (ISO member bodies) of various countries. The formulation of international standards is usually carried out through ISO technical committees. Each member body can also participate in the committee if it is interested in the project carried out by a technical committee. International organizations, both governmental and non-governmental, associated with ISO may also participate in this work. ISO has close links with the International Electrotechnical Commission (IEC) in the field of electrotechnical standardization. Draft international standards adopted by the technical committee are circulated to all member bodies for voting. The official publication of international standards requires at least 75% of the member bodies to vote in favor.
International Standard ISO898-5 was prepared by ISO/TC2 Technical Committee SC1 Mechanical Properties of Fasteners, Subcommittee. The second edition is a technical revision of the first edition (ISO898-5:1980) with deletions and additions. The general name of ISO898 is "Mechanical properties of carbon steel and alloy steel fasteners", which includes the following parts: - Part 1: Bolts, screws and studs
- Part 2 Coarse pitch threads for nuts with specified proof load values Part 5: Set screws and similar threaded fasteners not subject to tensile stress Part 6: Fine pitch threads for nuts with specified proof load values Part 7: Torque test and minimum torque for bolts and screws Appendix A of this standard is a prompt appendix.
Nominal diameter 1～10 mm
1 Scope
National Standard of the People's Republic of China
Mechanical properties of fasteners-Set screws
GB/T3098.3-
idt Iso 898-5:1998
Replaces GB/T 3098.3~-1982
This standard specifies the mechanical properties of set screws and similar fasteners not subject to tensile stress, with a nominal thread diameter of 1.6～24 mm, made of carbon steel or alloy steel, when tested at an ambient temperature of 10～35℃. Products judged to comply with this standard under this ambient temperature condition may have different mechanical and physical properties at higher or lower temperatures, and users should pay attention to this.
This standard does not apply to set screws with special performance requirements, such as: specified tensile stress (GB/T3098.1);
weldability;
corrosion resistance (GB/T3098.16);
performance requirements for working temperatures above +300℃ or below -50℃. Note: Set screws made of free-cutting steel cannot be used for temperatures above +250℃. 2 Reference standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T230-1991Method for testing Rockwell hardness of metals GB/T231—1984Method for testing Brinell hardness of metals GB/T 3098. 1-—2000
Mechanical properties of fasteners Bolts, screws and studs (idtISO898-1:1999) GB/T3098.16--2000Mechanical properties of fasteners Stainless steel set screws (idtISO3506-3:1997)Metal Vickers hardness test Part 1: Test method (eqvISO6507-1:1997) GB/T 4340.1—1999
3Marking system
The performance grade is marked with a code, as shown in Table 1. The digital part of the code represents 1/10 of the lowest Vickers hardness. The letter H in the code represents hardness.
Table 1 Marking of performance grade
Performance grade
Vickers hardness HVmin
Approved by the State Administration of Quality and Technical Supervision on September 26, 2000 22H
Implementation on February 1, 2001
4 Materials
GB/T 3098.3—2000
The materials for manufacturing set screws shall comply with the technical requirements specified in Table 2. When the guaranteed torque requirements specified in Article 6.3 are met, set screws with property grade 45H may also be made of other materials. Table 2 Material
Chemical composition, secretion
Property grade
Carbon steel 12.2)
Carbon steel"
Alloy steel 34
Heat treatment
Quenching and tempering
Quenching and tempering
Quenching and tempering
1) When free-cutting steel is used, the maximum content of lead, phosphorus and sulfur is: lead 0.35%; phosphorus 0.11%; sulfur 0.31%. 2) Square head purple set screws are allowed to be surface hardened. 3) The maximum lead content of 0.35% steel. 4) It should contain one or more chromium, nickel, molybdenum, vanadium or boron alloy elements. 5
Mechanical properties
When tested at ambient temperature according to the method specified in Chapter 6, the mechanical properties of the set screws shall comply with the provisions of Table 3. Table 3 Mechanical properties
Mechanical properties
Vickers hardness HV10
Brinell hardness HB, F=30D2
Rockwell hardness
Guaranteed torque
Minimum height of undecarburized layer of thread Emm
Maximum depth of fully decarburized layer Gmax+mm
Surface hardness HVo.3
1) There are no 14H, 22H and 33H grades for hexagon socket set screws. min
Performance grade\
2) If Rockwell hardness test is carried out, the minimum value of HRB test and the maximum value of HRC test shall be used for 22H grade. 3) For 45H grade, no complete decarburization layer is allowed
See Table 5
6 Test method
6.1 Hardness test
GB/T3098.3--2000
The hardness of the screw should be measured at the end of the screw and as close to the center as possible. If the maximum hardness specified in Table 3 is exceeded, it should be tested again on a section 0.5d from the end (d-nominal diameter of the thread). During acceptance, if there is any dispute, the Vickers hardness test shall prevail. The surface hardness shall be measured at the end of the screw. To ensure the accuracy of the measurement, the test part shall be ground or polished. 6.1.1 Vickers hardness test
The Vickers hardness test shall be in accordance with GB/T4340.1. 6.1.2 Brinell hardness testbzxZ.net
The Brinell hardness test shall be in accordance with GB/T231.
6.1.3 Rockwell hardness test
Rockwell hardness test shall be in accordance with GB/T230.
6.2 Decarburization test
---·Surface carbon potential assessment
Use appropriate measurement methods (6.2.2.1 or 6.2.2.2) to test on the longitudinal section of the thread to determine whether the height of the base metal area (E) and the depth of the full decarburization layer (G) are within the specified limits (Figure 1). The maximum value of G and the minimum value of E shall comply with the provisions of Table 3.
1—Complete decarburization layer; 2—Incomplete decarburization layer; 3: mid-diameter line; 4 base metal; H—Tooth profile height of external thread under maximum solid condition Figure 1 Decarburization distribution diagram
6.2.1 Definition
6.2.1.1 Base metal hardness
The hardness closest to the surface just before the increase or decrease in hardness caused by carburization or decarburization is shown (cross-section from the core to the outer diameter when testing).
6.2.1.2 Decarburization
Usually refers to the loss of carbon on the surface of ferrous metal materials (steel) 6.2.1.3 Incomplete decarburization
Decarburization that has caused a slight discoloration of tempered martensite due to the loss of carbon and has a hardness significantly lower than that of the adjacent base. 6.2.1.4 Complete decarburization
Due to the complete loss of carbon, only decarburization of ferrite structure can be seen in metallographic examination. 6.2.1.5 Carburization
The result of increasing the carbon content on the surface of the base metal. 6.2.2 Measurement method
6.2.2.1 Metallographic method
GB/T 3098.3-2000
This method can simultaneously determine the E value and the G value.
For the screw that has completed the heat treatment process, a longitudinal section of the test piece is cut along the center line of the thread from a position about half a diameter (1/2d) away from the end. For grinding and polishing, the test piece can be mounted in a fixture or preferably embedded in plastic. After mounting, the surface is ground and polished until it can be metallographically examined. Usually, immersion in 3% nital (a mixture of concentrated nitric acid and ethanol) can show the changes in the metallographic structure caused by decarburization.
Unless otherwise agreed with the user, the inspection should be magnified 100 times. If the microscope has a ground glass screen, the degree of decarburization can be directly measured with the help of a scale. If measuring with an eyepiece, one with a crosshair or scale should be used.
6.2.2.2 Hardness method (arbitration method for incomplete decarburization) The hardness measurement method is only applicable to threads with a pitch P ≥ 1.25 mm. However, for grade 45H, it is applicable to all specifications. Measure the Vickers hardness at the three points shown in Figure 2. The E value is as specified in Table 4. The test force should be 300 g. HV, ≥ HV, -30
HV, ≤ HV, +30
1,23-Measuring point: 4 mid-diameter line
Figure 2 Hardness measurement of decarburized layer
Table 4H and E values
Pitch P
0.3070.368
0.4290.491
1.0741.2271.5341.8402.1172.4540.6130.767.0.920
22H0.1540.1840.2150.2450.3070.3840.46033H0.20 50.
.5370.6140.7670.9201.0741.227.2860.3270.4090.5110.6130.7160.8181.0231.2271.4311.63645H0.2300.2760.
.3220.3680.4600.5750.690
0.8060. 9201
1. 1511. 3801. 6101. 841
The hardness at point 3 shall be on the thread mid-diameter line and measured on the tooth adjacent to the one at point 1 and point 2. The Vickers hardness value at point 2 shall be equal to or greater than the hardness value at point 1 minus 30 Vickers hardness units. At this time, the height E of the undecarburized layer shall at least comply with the provisions of Table 4.
The Vickers hardness value at point 3 shall be equal to or less than the hardness value at point 1 plus 30 Vickers hardness units. Higher than 30 Vickers hardness units indicates carburization, which is not allowed. If the full decarburized layer reaches the maximum value specified in Table 3, the hardness method cannot be used. Note: It should be distinguished whether the increase in hardness is caused by carburization or heat treatment or surface cold work hardening. 6.345H grade hexagon socket set screw proof torque test 45HI grade hexagon socket set screws shall comply with the proof torque test specified in Table 5. 104
Nominal thread diameter
GB/T 3098.3--2000
Table 5 Guaranteed torque
Minimum length of test screw, mm
Cylindrical end
Guaranteed torque
Screw the set screw into the test fixture, as shown in Figure 3, until the top surface of the screw is flush with the test fixture and should be against the supporting end on the base (if a supporting screw is screwed in from the other end). 1-Torque wrench; 2-Test screw; 3-Test fixture: hardness ≥50HRC; internal thread tolerance 5H; 4-Support screw: hardness 450570HV
Figure 3 Torque test device
Test hexagonal wrench: tolerance of width across flats is h9; minimum value of diagonal width should be ≥1.13smin hardness is 55～60HRC; and should be engaged at the full depth of the hexagonal socket of the set screw. The screw should be able to withstand the guaranteed torque specified in Table 3, and the surface should not break, crack or thread stripping.
Note: Damage caused by the torque test should not be used as a basis for rejection. 105
Marking of performance grade
GB/T3098.3—2000
Usually, it is not required to mark the performance grade of the set screw according to the provisions of Chapter 3. In special cases, it can be marked according to the specified performance grade code after agreement between the supply and demand parties. Trademark (identification) mark
The trademark or identification mark of the sign maker is not required. 1063--2000
The hardness of the screw should be measured at the end of the screw and as close to the center as possible. If the maximum hardness specified in Table 3 is exceeded, it should be tested again on a section 0.5d from the end (d--nominal diameter of the thread). During acceptance, if there is any dispute, the Vickers hardness test shall prevail. The surface hardness should be measured at the end of the screw. To ensure the accuracy of the measurement, the test part should be ground or polished. 6.1.1 Vickers hardness test
The Vickers hardness test shall be in accordance with GB/T4340.1. 6.1.2 Brinell hardness test
The Brinell hardness test shall be in accordance with GB/T231.
6.1.3 Rockwell hardness test
The Rockwell hardness test shall be in accordance with GB/T230.
6.2 Decarburization test
---· Surface carbon potential assessment
Use appropriate measurement methods (6.2.2.1 or 6.2.2.2) to test on the longitudinal section of the thread to determine whether the height of the base metal zone (E) and the depth of the fully decarburized layer (G) are within the specified limits (Figure 1). The maximum value of G and the minimum value of E shall comply with the provisions of Table 3.
1-Fully decarburized layer; 2-Incompletely decarburized layer; 3: Pitch line; 4 Base metal; H-Height of the tooth profile of the external thread under maximum solid condition Figure 1 Decarburization distribution diagram
6.2.1 Definitions
6.2.1.1 Base metal hardness
The hardness closest to the surface just before the increase or decrease in hardness caused by carburization or decarburization is shown (cross-section from the core to the outside diameter when testing).
6.2.1.2 Decarburization
Usually refers to the loss of carbon on the surface of ferrous metal materials (steel) 6.2.1.3 Incomplete decarburization
Decarburization due to the loss of carbon has caused the tempered martensite to slightly change color, and the hardness is significantly lower than the hardness of the adjacent matrix. 6.2.1.4 Complete decarburization
Due to the complete loss of carbon, only the decarburization of ferrite structure can be seen in the metallographic examination. 6.2.1.5 Carburization
The result of increasing the carbon content on the surface of the base metal. 6.2.2 Measurement method
6.2.2.1 Metallographic method
GB/T 3098.3—2000
This method can simultaneously determine the E value and G value.
For screws that have completed the heat treatment process, a longitudinal section of the test piece is cut along the center line of the thread from a position approximately half the diameter (1/2d) from the end. For grinding and polishing, the test piece can be mounted in a fixture or preferably embedded in plastic. After mounting, the surface is ground and polished until metallographic examination can be carried out. Usually, immersion in 3% nital (a mixture of concentrated nitric acid and ethanol) can show the changes in the metallographic structure caused by decarburization.
Unless otherwise agreed with the user, the inspection should be magnified 100 times. If the microscope has a ground glass screen, the degree of decarburization can be measured directly with the help of a scale. If measured with an eyepiece, a crosshair or scale should be used.
6.2.2.2 Hardness method (arbitration method for incomplete decarburization) The hardness measurement method is only applicable to threads with a pitch P ≥ 1.25 mm. However, for grade 45H, it is applicable to all specifications. The Vickers hardness is measured at the three points shown in Figure 2. The E value is specified in Table 4. The test force should be 300g. HV,≥HV,-30
HV,≤HV,+30
1,23-Measuring point: 4 mid-diameter line
Figure 2 Hardness measurement of decarburized layer
Table 4 Values of H and E
Pitch P
0.3070.368
0.4290.491
1.0741.2271.5341.8402.1172.4540.6130.767.0.920
22H0.1540.1840.2150.2450.3070.3840.46033H0.20 50.
.5370.6140.7670.9201.0741.227.2860.3270.4090.5110.6130.7160.8181.0231.2271.4311.63645H0.2300.2760.
.3220.3680.4600.5750.690
0.8060. 9201
1. 1511. 3801. 6101. 841
The hardness at point 3 shall be on the thread mid-diameter line and measured on the tooth adjacent to the one at point 1 and point 2. The Vickers hardness value at point 2 shall be equal to or greater than the hardness value at point 1 minus 30 Vickers hardness units. At this time, the height E of the undecarburized layer shall at least comply with the provisions of Table 4.
The Vickers hardness value at point 3 shall be equal to or less than the hardness value at point 1 plus 30 Vickers hardness units. Higher than 30 Vickers hardness units indicates carburization, which is not allowed. If the full decarburized layer reaches the maximum value specified in Table 3, the hardness method cannot be used. Note: It should be distinguished whether the increase in hardness is caused by carburization or heat treatment or surface cold work hardening. 6.345H grade hexagon socket set screw proof torque test 45HI grade hexagon socket set screws shall comply with the proof torque test specified in Table 5. 104
Nominal thread diameter
GB/T 3098.3--2000
Table 5 Guaranteed torque
Minimum length of test screw, mm
Cylindrical end
Guaranteed torque
Screw the set screw into the test fixture, as shown in Figure 3, until the top surface of the screw is flush with the test fixture and should be against the supporting end on the base (if a supporting screw is screwed in from the other end). 1-Torque wrench; 2-Test screw; 3-Test fixture: hardness ≥50HRC; internal thread tolerance 5H; 4-Support screw: hardness 450570HV
Figure 3 Torque test device
Test hexagonal wrench: tolerance of width across flats is h9; minimum value of diagonal width should be ≥1.13smin hardness is 55～60HRC; and should be engaged at the full depth of the hexagonal socket of the set screw. The screw should be able to withstand the guaranteed torque specified in Table 3, and the surface should not break, crack or thread stripping.
Note: Damage caused by the torque test should not be used as a basis for rejection. 105
Marking of performance grade
GB/T3098.3—2000
Usually, it is not required to mark the performance grade of the set screw according to the provisions of Chapter 3. In special cases, it can be marked according to the specified performance grade code after agreement between the supply and demand parties. Trademark (identification) mark
The trademark or identification mark of the sign maker is not required. 1063--2000
The hardness of the screw should be measured at the end of the screw and as close to the center as possible. If the maximum hardness specified in Table 3 is exceeded, it should be tested again on a section 0.5d from the end (d--nominal diameter of the thread). During acceptance, if there is any dispute, the Vickers hardness test shall prevail. The surface hardness should be measured at the end of the screw. To ensure the accuracy of the measurement, the test part should be ground or polished. 6.1.1 Vickers hardness test
The Vickers hardness test shall be in accordance with GB/T4340.1. 6.1.2 Brinell hardness test
The Brinell hardness test shall be in accordance with GB/T231.
6.1.3 Rockwell hardness test
The Rockwell hardness test shall be in accordance with GB/T230.
6.2 Decarburization test
---· Surface carbon potential assessment
Use appropriate measurement methods (6.2.2.1 or 6.2.2.2) to test on the longitudinal section of the thread to determine whether the height of the base metal zone (E) and the depth of the fully decarburized layer (G) are within the specified limits (Figure 1). The maximum value of G and the minimum value of E shall comply with the provisions of Table 3.
1-Fully decarburized layer; 2-Incompletely decarburized layer; 3: Pitch line; 4 Base metal; H-Height of the tooth profile of the external thread under maximum solid condition Figure 1 Decarburization distribution diagram
6.2.1 Definitions
6.2.1.1 Base metal hardness
The hardness closest to the surface just before the increase or decrease in hardness caused by carburization or decarburization is shown (cross-section from the core to the outside diameter when testing).
6.2.1.2 Decarburization
Usually refers to the loss of carbon on the surface of ferrous metal materials (steel) 6.2.1.3 Incomplete decarburization
Decarburization due to the loss of carbon has caused the tempered martensite to slightly change color, and the hardness is significantly lower than the hardness of the adjacent matrix. 6.2.1.4 Complete decarburization
Due to the complete loss of carbon, only the decarburization of ferrite structure can be seen in the metallographic examination. 6.2.1.5 Carburization
The result of increasing the carbon content on the surface of the base metal. 6.2.2 Measurement method
6.2.2.1 Metallographic method
GB/T 3098.3—2000
This method can simultaneously determine the E value and G value.
For screws that have completed the heat treatment process, a longitudinal section of the test piece is cut along the center line of the thread from a position approximately half the diameter (1/2d) from the end. For grinding and polishing, the test piece can be mounted in a fixture or preferably embedded in plastic. After mounting, the surface is ground and polished until metallographic examination can be carried out. Usually, immersion in 3% nital (a mixture of concentrated nitric acid and ethanol) can show the changes in the metallographic structure caused by decarburization.
Unless otherwise agreed with the user, the inspection should be magnified 100 times. If the microscope has a ground glass screen, the degree of decarburization can be measured directly with the help of a scale. If measured with an eyepiece, a crosshair or scale should be used.
6.2.2.2 Hardness method (arbitration method for incomplete decarburization) The hardness measurement method is only applicable to threads with a pitch P ≥ 1.25 mm. However, for grade 45H, it is applicable to all specifications. The Vickers hardness is measured at the three points shown in Figure 2. The E value is specified in Table 4. The test force should be 300g. HV,≥HV,-30
HV,≤HV,+30
1,23-Measuring point: 4 mid-diameter line
Figure 2 Hardness measurement of decarburized layer
Table 4 Values of H and E
Pitch P
0.3070.368
0.4290.491
1.0741.2271.5341.8402.1172.4540.6130.767.0.920
22H0.1540.1840.2150.2450.3070.3840.46033H0.20 50.
.5370.6140.7670.9201.0741.227.2860.3270.4090.5110.6130.7160.8181.0231.2271.4311.63645H0.2300.2760.
.3220.3680.4600.5750.690
0.8060. 9201
1. 1511. 3801. 6101. 841
The hardness at point 3 shall be on the thread mid-diameter line and measured on the tooth adjacent to the one at point 1 and point 2. The Vickers hardness value at point 2 shall be equal to or greater than the hardness value at point 1 minus 30 Vickers hardness units. At this time, the height E of the undecarburized layer shall at least comply with the provisions of Table 4.
The Vickers hardness value at point 3 shall be equal to or less than the hardness value at point 1 plus 30 Vickers hardness units. Higher than 30 Vickers hardness units indicates carburization, which is not allowed. If the full decarburized layer reaches the maximum value specified in Table 3, the hardness method cannot be used. Note: It should be distinguished whether the increase in hardness is caused by carburization or heat treatment or surface cold work hardening. 6.345H grade hexagon socket set screw proof torque test 45HI grade hexagon socket set screws shall comply with the proof torque test specified in Table 5. 104
Nominal thread diameter
GB/T 3098.3--2000
Table 5 Guaranteed torque
Minimum length of test screw, mm
Cylindrical end
Guaranteed torque
Screw the set screw into the test fixture, as shown in Figure 3, until the top surface of the screw is flush with the test fixture and should be against the supporting end on the base (if a supporting screw is screwed in from the other end). 1-Torque wrench; 2-Test screw; 3-Test fixture: hardness ≥50HRC; internal thread tolerance 5H; 4-Support screw: hardness 450570HV
Figure 3 Torque test device
Test hexagonal wrench: tolerance of width across flats is h9; minimum value of diagonal width should be ≥1.13smin hardness is 55～60HRC; and should be engaged at the full depth of the hexagonal socket of the set screw. The screw should be able to withstand the guaranteed torque specified in Table 3, and the surface should not break, crack or thread stripping.
Note: Damage caused by the torque test should not be used as a basis for rejection. 105
Marking of performance grade
GB/T3098.3—2000
Usually, it is not required to mark the performance grade of the set screw according to the provisions of Chapter 3. In special cases, it can be marked according to the specified performance grade code after agreement between the supply and demand parties. Trademark (identification) mark
The trademark or identification mark of the sign maker is not required. 1063—2000
This method can determine both the E and G values.
For screws that have completed the heat treatment process, a longitudinal section of the test piece is cut along the center line of the thread from a position approximately half the diameter (1/2d) from the end. For grinding and polishing, the test piece can be mounted in a fixture or preferably embedded in plastic. After mounting, the surface is ground and polished until metallographic examination can be carried out. Usually, immersion in 3% nital (a mixture of concentrated nitric acid and ethanol) can show the changes in the metallographic structure caused by decarburization.
Unless otherwise agreed with the user, the examination should be magnified 100 times. If the microscope has a ground glass screen, the degree of decarburization can be measured directly with the help of a scale. If the eyepiece is used for measurement, a crosshair or scale should be used.
6.2.2.2 Hardness method (arbitration method for incomplete decarburization) The hardness measurement method is only applicable to threads with a pitch P ≥ 1.25 mm. However, for 45H grade, it applies to all specifications. Measure the Vickers hardness at the three points shown in Figure 2. The E value is specified in Table 4. The test force should be 300g. HV,≥HV,-30
HV,≤HV,+30
1,23-Measurement point: 4 mid-diameter line
Figure 2 Hardness measurement of decarburized layer
Table 4H and E values
Pitch P
0.3070.368
0.4290.491
1.0741.2271.5341.8402.1172.4540.6130.767.0.920
22H0.1540.1840.2150.2450.3070.3840.46033H0.20 50.
.5370.6140.7670.9201.0741.227.2860.3270.4090.5110.6130.7160.8181.0231.2271.4311.63645H0.2300.2760.
.3220.3680.4600.5750.690
0.8060. 9201
1. 1511. 3801. 6101. 841
The hardness at point 3 shall be on the thread mid-diameter line and measured on the tooth adjacent to the one at point 1 and point 2. The Vickers hardness value at point 2 shall be equal to or greater than the hardness value at point 1 minus 30 Vickers hardness units. At this time, the height E of the undecarburized layer shall at least comply with the provisions of Table 4.
The Vickers hardness value at point 3 shall be equal to or less than the hardness value at point 1 plus 30 Vickers hardness units. Higher than 30 Vickers hardness units indicates carburization, which is not allowed. If the full decarburized layer reaches the maximum value specified in Table 3, the hardness method cannot be used. Note: It should be distinguished whether the increase in hardness is caused by carburization or heat treatment or surface cold work hardening. 6.345H grade hexagon socket set screw proof torque test 45HI grade hexagon socket set screws shall comply with the proof torque test specified in Table 5. 104
Nominal thread diameter
GB/T 3098.3--2000
Table 5 Guaranteed torque
Minimum length of test screw, mm
Cylindrical end
Guaranteed torque
Screw the set screw into the test fixture, as shown in Figure 3, until the top surface of the screw is flush with the test fixture and should be against the supporting end on the base (if a supporting screw is screwed in from the other end). 1-Torque wrench; 2-Test screw; 3-Test fixture: hardness ≥50HRC; internal thread tolerance 5H; 4-Support screw: hardness 450570HV
Figure 3 Torque test device
Test hexagonal wrench: tolerance of width across flats is h9; minimum value of diagonal width should be ≥1.13smin hardness is 55～60HRC; and should be engaged at the full depth of the hexagonal socket of the set screw. The screw should be able to withstand the guaranteed torque specified in Table 3, and the surface should not break, crack or thread stripping.
Note: Damage caused by the torque test should not be used as a basis for rejection. 105
Marking of performance grade
GB/T3098.3—2000
Usually, it is not required to mark the performance grade of the set screw according to the provisions of Chapter 3. In special cases, it can be marked according to the specified performance grade code after agreement between the supply and demand parties. Trademark (identification) mark
The trademark or identification mark of the sign maker is not required. 1063—2000
This method can determine both the E and G values.
For screws that have completed the heat treatment process, a longitudinal section of the test piece is cut along the center line of the thread from a position approximately half the diameter (1/2d) from the end. For grinding and polishing, the test piece can be mounted in a fixture or preferably embedded in plastic. After mounting, the surface is ground and polished until metallographic examination can be carried out. Usually, immersion in 3% nital (a mixture of concentrated nitric acid and ethanol) can show the changes in the metallographic structure caused by decarburization.
Unless otherwise agreed with the user, the examination should be magnified 100 times. If the microscope has a ground glass screen, the degree of decarburization can be measured directly with the help of a scale. If the eyepiece is used for measurement, a crosshair or scale should be used.
6.2.2.2 Hardness method (arbitration method for incomplete decarburization) The hardness measurement method is only applicable to threads with a pitch P ≥ 1.25 mm. However, for 45H grade, it applies to all specifications. Measure the Vickers hardness at the three points shown in Figure 2. The E value is specified in Table 4. The test force should be 300g. HV,≥HV,-30
HV,≤HV,+30
1,23-Measurement point: 4 mid-diameter line
Figure 2 Hardness measurement of decarburized layer
Table 4H and E values
Pitch P
0.3070.368
0.4290.491
1.0741.2271.5341.8402.1172.4540.6130.767.0.920
22H0.1540.1840.2150.2450.3070.3840.46033H0.20 50.
.5370.6140.7670.9201.0741.227.2860.3270.4090.5110.6130.7160.8181.0231.2271.4311.63645H0.2300.2760.
.3220.3680.4600.5750.690
0.8060. 9201
1. 1511. 3801. 6101. 841
The hardness at point 3 shall be on the thread mid-diameter line and measured on the tooth adjacent to the one at point 1 and point 2. The Vickers hardness value at point 2 shall be equal to or greater than the hardness value at point 1 minus 30 Vickers hardness units. At this time, the height E of the undecarburized layer shall at least comply with the provisions of Table 4.
The Vickers hardness value at point 3 shall be equal to or less than the hardness value at point 1 plus 30 Vickers hardness units. Higher than 30 Vickers hardness units indicates carburization, which is not allowed. If the full decarburized layer reaches the maximum value specified in Table 3, the hardness method cannot be used. Note: It should be distinguished whether the increase in hardness is caused by carburization or heat treatment or surface cold work hardening. 6.345H grade hexagon socket set screw proof torque test 45HI grade hexagon socket set screws shall comply with the proof torque test specified in Table 5. 104
Nominal thread diameter
GB/T 3098.3--2000
Table 5 Guaranteed torque
Minimum length of test screw, mm
Cylindrical end
Guaranteed torque
Screw the set screw into the test fixture, as shown in Figure 3, until the top surface of the screw is flush with the test fixture and should be against the supporting end on the base (if a supporting screw is screwed in from the other end). 1-Torque wrench; 2-Test screw; 3-Test fixture: hardness ≥50HRC; internal thread tolerance 5H; 4-Support screw: hardness 450570HV
Figure 3 Torque test device
Test hexagonal wrench: tolerance of width across flats is h9; minimum value of diagonal width should be ≥1.13smin hardness is 55～60HRC; and should be engaged at the full depth of the hexagonal socket of the set screw. The screw should be able to withstand the guaranteed torque specified in Table 3, and the surface should not break, crack or thread stripping.
Note: Damage caused by the torque test should not be used as a basis for rejection. 105
Marking of performance grade
GB/T3098.3—2000
Usually, it is not required to mark the performance grade of the set screw according to the provisions of Chapter 3. In special cases, it can be marked according to the specified performance grade code after agreement between the supply and demand parties. Trademark (identification) mark
The trademark or identification mark of the sign maker is not required. 1063—2000
Normally, it is not required to mark the performance grade of set screws in accordance with the provisions of Chapter 3. In special cases, upon agreement between the supplier and the buyer, they may be marked according to the specified performance grade code. Trademark (identification) marking
It is not required to mark the manufacturer's trademark or identification mark. 1063—2000
Normally, it is not required to mark the performance grade of set screws in accordance with the provisions of Chapter 3. In special cases, upon agreement between the supplier and the buyer, they may be marked according to the specified performance grade code. Trademark (identification) marking
It is not required to mark the manufacturer's trademark or identification mark. 106
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