Material Requirements for Bolts, Screws, and Studs (GB/T 3098.1-2000)

1. Material Requirements for Bolts, Screws, and Studs (GB/T 3098.1-2000)

Performance grades, material, heat treatment, chemical composition (%), tempering temperature (℃)

Performance Grade

Material

Heat Treatment

C max

P max

S max

Mn min

Other Notes

Tempering Temp (℃)

Carbon Steel

—

—

0.20

0.06

0.003

—

—

4.6

Carbon Steel

—

—

0.55

0.06

0.003

—

—

4.8

Carbon Steel

—

—

0.55

0.066

0.003

—

—

6.8

Low-carbon alloy steel (B, Mn, or Cr), quenched & tempered / Medium-carbon steel, quenched & tempered

—

Q&T

0.15

0.035

0.003

0.25-0.55

—

9.8

Low-carbon alloy steel (B, Mn, or Cr), Q&T

—

Q&T

0.15

0.035

0.003

0.25-0.55

—

10.9

Medium-carbon steel or alloy steel, Q&T

—

Q&T

0.20-0.25

0.035

0.003

0.25-0.55

Contains Cr, Ni, Mo, V, or B

10.9, 12.9

Notes:

1. Boron content up to 0.005%; inactive boron controlled by Ti and/or Al addition.

2. Grades allow use of free-machining steel; max contents: S 0.34%, P 0.11%, Pb 0.35%.

3. Fasteners >20 mm diameter must use steel specified for grade 10.9 for good hardenability.

4. For low-carbon alloy steels <0.25%C, minimum Mn content: grade 8.8: 0.6%, grades 9.8, 10.9: 0.7%.

5. Grade 10.9 should meet all requirements for 10.9 grade; lower tempering temperatures may reduce stress resistance.

6. Materials must have good hardenability to achieve ~90% martensite in thread core after quenching, before tempering.

7. Alloy steel must contain at least one of: Cr ≥0.3%, Ni ≥0.3%, Mo ≥0.2%, V ≥0.1%.

8. For grade 12.9, surface must have no visible white phosphorus segregation.

9. Some chemical compositions and tempering temperatures are still under investigation.

2. Nuts

2.1 Nuts (Coarse Thread) – GB/T 3098.2-2000

Performance Grade

C max

Mn min

P max

S max

Notes

4,5,6

—

0.50

—

0.06

Can be made from free-machining steel; S ≤0.30%, P ≤0.11%, Pb ≤0.35%

8,10,12

0.58

0.25-0.45

0.06-0.048

0.15-0.058

Quenched and tempered for performance

2.2 Nuts (Fine Thread) – GB/T 3098.4-2000

Performance Grade

C max

Mn min

P max

S max

Notes

5,6,8,10,12

0.58

0.25-0.45

0.06-0.048

0.15-0.058

Similar heat treatment and material notes as coarse thread nuts

2.3 Rivet Nuts – GB/T 17880.6-1999

Type

Material

Standard

Steel flat head, countersunk, small countersunk

08F, ML10

GB/T 699, GB/T 6478

Aluminum alloy

5056 (formerly LF5-1), 6061 (formerly LD30)

GB/T 3190

2.4 Torque-efficient steel hex lock nuts – GB 3098.9-93

· Nut body material same as coarse-thread nuts.

· Material for metal or non-metal inserts determined by manufacturer.

 

3. Set Screws – GB/T 3098.3-2000

Performance Grade

Material

Heat Treatment

C max

P max

S max

Notes

14H

Carbon steel

—

0.50

0.15

0.11

Free-machining steel max S,P,Pb: Pb 0.35%, P 0.11%, S 0.34%

22H

Carbon steel

Q&T

0.50

0.05

0.05

Surface hardening allowed

33H

Carbon steel

Q&T

0.50

0.05

0.05

Alloying elements: Cr, Ni, Mo, V, B

45H

Alloy steel

Q&T

0.50

0.05

0.05

Must meet guaranteed torque requirements per GB/T 3098.3-2000

 

 

4. High-temperature Threaded Fasteners – GB/T 3098.8-92

· For use above +300℃ and under alternating loads while retaining preload and fatigue strength.

· Material examples:

 

Temp (℃)

Bolt/Stud

Nut

Standard

400

35A45

35

GB699

500

30CrMo

35CrMoA

GB3077

600

2Cr12WMoVNbB

20CrMoV

YB/Z8

Notes:

1. Bolts/studs should be 30–50 HB harder than nuts.

2. Sleeve material should match stud.

3. Materials must pass low-magnification microstructure inspection; porosity and segregation must meet GB1979 level 2.

 

5. Stainless Steel Fasteners

· Bolts, screws, studs (GB/T 3098.3-2000), nuts (GB/T 3098.15-2000), set screws (GB/T 3098.16-2000) use stainless steel per national standards.

· Unless agreed, composition within specified steel group range, chosen by manufacturer.

· For intergranular corrosion prone situations, ISO 3651-1 or 3651-2 tests recommended.

· Prefer stabilized A3, A5 or low-C (≤0.03%) A2, A4 types.

· Table 1 – Stainless Steel Groups and Chemical Composition (%)

Group

C

S

Mn

P

Cr

Mo

Ni

Cu

Notes

Austenitic A1–A5

0.08–0.12

≤0.03

12–20

0.045–0.05

16–19

0–2.25

0.75–1.75

0–2.25

—

Martensitic C1–C4

0.08–0.17

≤0.15

1.5–1.7

0.06

11.5–16

0–1.5

—

—

—

Ferritic F1–F2

0.12

≤0.04

15–18

0.03

—

—

—

—

—

Notes:

1. Values are maxima unless noted.

2. S can be replaced by Se.

3. For Ni <8%, Mn min = 5%.

4. For Ni >8%, no min Cu requirement.
5–12. Mo, Ti, Nb, Ta content and rules for large diameters as per standard.

 

6. Non-ferrous Fasteners – GB 3098.10-93

Performance Grade

Material

Standard

CU1–CU7

Cu-ETP, CuZn37, CuZn39Pb3, CuSn6, CuNiSi, CuZn40Mn1Pb, CuAl10Ni5Fe4

ISO/GB numbers

AL1–AL6

AlMg3, AlMg5, AlSi1MgMn, AlCu4MgSi, AlZnMgCu0.5, AlZn5.5MgCu

ISO/GB numbers

· Alternative materials allowed if mechanical properties guaranteed.

· Manufacturer determines heat treatment as needed.

 

7. Self-tapping Screws

7.1 Self-drilling & self-tapping screws – GB/T 3098.11-1995

Material

C

Mn

P

S

Notes

20Mn, 15MnB

0.13–0.27

0.64–1.71

0.04

0.042

Boron 0.05–0.30% allowed

7.2 Cold-formed self-tapping screws (GB 3098.7-2000)

· Carburized and cold-headed; chemical composition limits are guidelines.

· Boron ≤0.005% if controlled by Ti/Al.

 

7.3 Wood Screws – GB 922-86

Type

Material

Standard

Carbon steel

Q215, Q235

GB700

Copper & Cu-alloy

H62, HPb59-1

GB4424, GB4425

 

1. Material Requirements for Bolts, Screws, and Studs (GB/T 3098.1-2000)

Performance grades, material, heat treatment, chemical composition (%), tempering temperature (℃)

Performance Grade

Material

Heat Treatment

C max

P max

S max

Mn min

Other Notes

Tempering Temp (℃)

Carbon Steel

—

—

0.20

0.06

0.003

—

—

4.6

Carbon Steel

—

—

0.55

0.06

0.003

—

—

4.8

Carbon Steel

—

—

0.55

0.066

0.003

—

—

6.8

Low-carbon alloy steel (B, Mn, or Cr), quenched & tempered / Medium-carbon steel, quenched & tempered

—

Q&T

0.15

0.035

0.003

0.25-0.55

—

9.8

Low-carbon alloy steel (B, Mn, or Cr), Q&T

—

Q&T

0.15

0.035

0.003

0.25-0.55

—

10.9

Medium-carbon steel or alloy steel, Q&T

—

Q&T

0.20-0.25

0.035

0.003

0.25-0.55

Contains Cr, Ni, Mo, V, or B

10.9, 12.9

Notes:

1. Boron content up to 0.005%; inactive boron controlled by Ti and/or Al addition.

2. Grades allow use of free-machining steel; max contents: S 0.34%, P 0.11%, Pb 0.35%.

3. Fasteners >20 mm diameter must use steel specified for grade 10.9 for good hardenability.

4. For low-carbon alloy steels <0.25%C, minimum Mn content: grade 8.8: 0.6%, grades 9.8, 10.9: 0.7%.

5. Grade 10.9 should meet all requirements for 10.9 grade; lower tempering temperatures may reduce stress resistance.

6. Materials must have good hardenability to achieve ~90% martensite in thread core after quenching, before tempering.

7. Alloy steel must contain at least one of: Cr ≥0.3%, Ni ≥0.3%, Mo ≥0.2%, V ≥0.1%.

8. For grade 12.9, surface must have no visible white phosphorus segregation.

9. Some chemical compositions and tempering temperatures are still under investigation.

2. Nuts

2.1 Nuts (Coarse Thread) – GB/T 3098.2-2000

Performance Grade

C max

Mn min

P max

S max

Notes

4,5,6

—

0.50

—

0.06

Can be made from free-machining steel; S ≤0.30%, P ≤0.11%, Pb ≤0.35%

8,10,12

0.58

0.25-0.45

0.06-0.048

0.15-0.058

Quenched and tempered for performance

2.2 Nuts (Fine Thread) – GB/T 3098.4-2000

Performance Grade

C max

Mn min

P max

S max

Notes

5,6,8,10,12

0.58

0.25-0.45

0.06-0.048

0.15-0.058

Similar heat treatment and material notes as coarse thread nuts

2.3 Rivet Nuts – GB/T 17880.6-1999

Type

Material

Standard

Steel flat head, countersunk, small countersunk

08F, ML10

GB/T 699, GB/T 6478

Aluminum alloy

5056 (formerly LF5-1), 6061 (formerly LD30)

GB/T 3190

2.4 Torque-efficient steel hex lock nuts – GB 3098.9-93

· Nut body material same as coarse-thread nuts.

· Material for metal or non-metal inserts determined by manufacturer.

 

3. Set Screws – GB/T 3098.3-2000

Performance Grade

Material

Heat Treatment

C max

P max

S max

Notes

14H

Carbon steel

—

0.50

0.15

0.11

Free-machining steel max S,P,Pb: Pb 0.35%, P 0.11%, S 0.34%

22H

Carbon steel

Q&T

0.50

0.05

0.05

Surface hardening allowed

33H

Carbon steel

Q&T

0.50

0.05

0.05

Alloying elements: Cr, Ni, Mo, V, B

45H

Alloy steel

Q&T

0.50

0.05

0.05

Must meet guaranteed torque requirements per GB/T 3098.3-2000

 

 

4. High-temperature Threaded Fasteners – GB/T 3098.8-92

· For use above +300℃ and under alternating loads while retaining preload and fatigue strength.

· Material examples:

 

Temp (℃)

Bolt/Stud

Nut

Standard

400

35A45

35

GB699

500

30CrMo

35CrMoA

GB3077

600

2Cr12WMoVNbB

20CrMoV

YB/Z8

Notes:

1. Bolts/studs should be 30–50 HB harder than nuts.

2. Sleeve material should match stud.

3. Materials must pass low-magnification microstructure inspection; porosity and segregation must meet GB1979 level 2.

 

5. Stainless Steel Fasteners

· Bolts, screws, studs (GB/T 3098.3-2000), nuts (GB/T 3098.15-2000), set screws (GB/T 3098.16-2000) use stainless steel per national standards.

· Unless agreed, composition within specified steel group range, chosen by manufacturer.

· For intergranular corrosion prone situations, ISO 3651-1 or 3651-2 tests recommended.

· Prefer stabilized A3, A5 or low-C (≤0.03%) A2, A4 types.

· Table 1 – Stainless Steel Groups and Chemical Composition (%)

Group

C

S

Mn

P

Cr

Mo

Ni

Cu

Notes

Austenitic A1–A5

0.08–0.12

≤0.03

12–20

0.045–0.05

16–19

0–2.25

0.75–1.75

0–2.25

—

Martensitic C1–C4

0.08–0.17

≤0.15

1.5–1.7

0.06

11.5–16

0–1.5

—

—

—

Ferritic F1–F2

0.12

≤0.04

15–18

0.03

—

—

—

—

—

Notes:

1. Values are maxima unless noted.

2. S can be replaced by Se.

3. For Ni <8%, Mn min = 5%.

4. For Ni >8%, no min Cu requirement.
5–12. Mo, Ti, Nb, Ta content and rules for large diameters as per standard.

 

6. Non-ferrous Fasteners – GB 3098.10-93

Performance Grade

Material

Standard

CU1–CU7

Cu-ETP, CuZn37, CuZn39Pb3, CuSn6, CuNiSi, CuZn40Mn1Pb, CuAl10Ni5Fe4

ISO/GB numbers

AL1–AL6

AlMg3, AlMg5, AlSi1MgMn, AlCu4MgSi, AlZnMgCu0.5, AlZn5.5MgCu

ISO/GB numbers

· Alternative materials allowed if mechanical properties guaranteed.

· Manufacturer determines heat treatment as needed.

 

7. Self-tapping Screws

7.1 Self-drilling & self-tapping screws – GB/T 3098.11-1995

Material

C

Mn

P

S

Notes

20Mn, 15MnB

0.13–0.27

0.64–1.71

0.04

0.042

Boron 0.05–0.30% allowed

7.2 Cold-formed self-tapping screws (GB 3098.7-2000)

· Carburized and cold-headed; chemical composition limits are guidelines.

· Boron ≤0.005% if controlled by Ti/Al.

 

7.3 Wood Screws – GB 922-86

Type

Material

Standard

Carbon steel

Q215, Q235

GB700

Copper & Cu-alloy

H62, HPb59-1

GB4424, GB4425