How to determine the matching bolts and nuts for flanges of different materials

How to choose matching bolts and nuts for flanges of different materials:

1. Material requirements for bolts, screws and studs (GB/T3098.1-2000)

Performance grade material and heat treatment chemical composition,% tempering temperature

℃

min

CP

maxS

maxB1)

max

minmax

3.62) Carbon steel 0.200.050.060.003

4.62)0.550.050.060.003

4.82)

5.60.130.550.050.060.003

5.82)0.550.050.06

6.82)

8.83) Low carbon alloy steel (such as boron, manganese or chromium), quenched and tempered or medium carbon steel, quenched and tempered 0.154) 0.040.0350.0350.003425

0.250.550.0350.035

9.8 Low carbon alloy steel (such as boron, manganese or chromium), quenched and tempered or medium carbon steel, quenched and tempered 0.154) 0.350.0350.0350.003425

0.250.550.0350.035

10.95), 6) Low carbon alloy steel (such as boron, manganese or chromium), quenched and tempered 0.154) 0.350.0350.0350.003340

10.96) Medium carbon steel, quenched and tempered or low and medium carbon alloy steel (such as boron, manganese or chromium), quenched and tempered or alloy steel quenched and tempered 7) 0.25

0.204)0.55

0.550.035

0.0350.035

0.0350.03425

0.200.550.0350.0350.003

10.96), 8), 9) alloy steel, quenched and tempered 7) 0.280.500.0350.0350.003380

1) The content of boron can reach 0.005%, and its ineffective boron can be controlled by adding titanium and (or) aluminum.

2) These performance levels allow easy-cut manufacturing, and the maximum content of sulfur, phosphorus and lead is: sulfur 0.34%; phosphorus 0.11%; lead 0.35%.

3) In order to ensure good hardenability, fasteners with a thread diameter of more than 20mm must be made of steel specified for 10.9.

4) The minimum manganese content of low-carbon alloy steel with carbon content of less than 0.25% (barrel sample analysis) is: 8.8: 0.6%; 9.8, 10.9 and 10.9: 0.7%.

5) The product should add a horizontal line mark under the performance level code. Class 10.9 should meet all the properties specified for class 10.9, and lower fire temperature will cause different degrees of stress weakening under the condition of raising temperature.

6) The material used for this performance level should have good hardenability to ensure that the core of the fastener thread section obtains about 90% martensite structure after quenching and before tempering.

7) Alloy steel should contain at least one of the following elements, the minimum content of which is: chromium 0.30%; nickel 0.30%; molybdenum 0.20%; vanadium 0.10%

8) Considering the tensile stress, the surface of 12.9 level is not allowed to have a white phosphorus accumulation layer that can be measured by metallography.

9) The chemical composition and tempering temperature are still under investigation.

Second, nut

1. Material technical requirements for nuts (fine thread) (GB/T3098.2-2000)

Performance grade chemical composition,%

C

maxMn

minP

maxS

max

41), 51), 61) 0.500.0600.150

8, 9041) 0.580.250.0600.150

102)051)0.580.300.0480.058

122)0.580.450.0480.058

1) This performance level can be made of free-cutting steel (unless otherwise agreed by the supplier and the demander), and the maximum content of sulfur, phosphorus and lead is: sulfur 0.30%; phosphorus 0.11%; lead 0.35%.

2) In order to improve the mechanical properties of the nut, alloy elements can be added when necessary.

The performance grades of 05, 8 (>M16 type l nuts), 10 and 12 grades of nuts should be quenched and tempered.

2. Material technical requirements for nuts (fine thread) (GB/T3098.4-2000)

Performance grade chemical composition:%

C

maxMn

minP

maxS

max

51), 60.500.0600.150

82)041) 0.580.250.0600.150

102)052)0.580.300.0480.058

122)0.580.450.0480.058

1) This performance level can be made of free-cutting steel (unless otherwise agreed by the supplier and the buyer), and the maximum content of sulfur, phosphorus and lead is: sulfur 0.34%; phosphorus 0.11%; lead 0.35%.

2) In order to improve the mechanical properties of the nut, alloy elements can be added when necessary.

Nuts with performance grades of 05, 8 (l-shaped nuts), 10 and 12 grades should be quenched and tempered.