CN105506496A - High-strength prestressing force bolt production method - Google Patents

Abstract

The present invention discloses a high-strength prestressing force bolt production method. According to the method, vacuum induction and electroslag re-melting are used to smelt medium-carbon alloy steel and control the content of impurities; a vacuum furnace is used to carry out a heat treatment, the quenching temperature is 860 DEG C, the first high-temperature tempering temperature is 560 DEG C, and the second tempering temperature is 500 DEG C; and machining is performed according to the required bolt specification, threads are processed in a thread rolling processing manner, the pitch diameter tolerance is controlled within 0.1 mm, the bolt surface roughness Ra and the thread roughness Ra are 0.8, and all transitional positions of the bolt adopts arc transition more than R20. According to the present invention, the produced bolt has advantages of high strength and high toughness, the mechanical property testing indicators meet the fastening of the member bearing the high alternating load, the safe and reliable operation of the member can be ensured, and the production cost and the production cycle are reduced.

Description

The making method of high-strength prestress bolt

Technical field

The present invention relates to a kind of making method of high-strength prestress bolt.

Background technology

In metallurgy industry, high-strength prestress bolt is mainly used in the cross-bearing location of mill's main drive shaft, because mill's main drive shaft bears larger repeated load in operation process, for the yield strength of bolt, toughness reguirements is very high, and cross-bearing involves great expense, therefore directly affects the safe reliability of mill's main drive shaft the work-ing life of bolt.

The cross-bearing tack bolt of current domestic main driving axle generally adopts carbon alloy material in 35CrMo, 30CrNiMo etc. to make.All barely satisfactory in mechanics properties testing indexs such as yield strength, impelling strength, relative reduction in area, the general one-period that uses must all be changed.The bolt that external like product makes as Japanese JIS standard alloy structure iron SNCM630 is in yield strength, and impelling strength, the mechanics properties testing indexs such as relative reduction in area all can reach requirement, but procurement price is expensive, and the cycle is long.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of material smelting of high-strength prestress bolt and the making method of bolt, the bolt that present method makes has the advantage of high strength, high tenacity, its mechanics properties testing index meets bears the fastening of larger repeated load parts, guarantee the safe and reliable operation of these parts, and reduce cost of manufacture and cycle.

For solving the problems of the technologies described above, the making method of high-strength prestress bolt of the present invention comprises the steps:

Step one, employing vacuum induction and electroslag heavily melt technique smelts medium carbon alloy steel, its elemental composition is C content 0.28-0.32wt%, Si content 0.20-0.30wt%, Mn content 0.45-0.55wt%, Cr content 2.7-3.2wt%, Ni content 2.8-3.5wt%, Mo content 0.55-0.65wt%, control P, S, H, O foreign matter content in medium carbon alloy steel, P content≤0.015wt%, S content≤0.005wt%, H content≤2ppm, O content≤20ppm, N content≤60ppm, reduce the impelling strength of impurity on medium carbon alloy steel and the impact of fatigue strength;

Step 2, employing vacuum oven are heat-treated the medium carbon alloy steel after smelting, preheating 650 DEG C, insulation 160min, 80 DEG C/h is warming up to 860 DEG C, and insulation 130min, 80 DEG C/h are cooled to first time tempering 560 DEG C, insulation 420min, be cooled to second time tempering 500 DEG C, insulation 360min, air cooling is to room temperature;

Step 3, according to required bolt specification, machining is carried out to the medium carbon alloy steel after thermal treatment, screw thread adopts accurate digital control rolled thread processing, central diameter allowance control is within 0.1mm, list of bolts surface roughness and screw thread roughness are Ra0.8, and all transit sites of bolt adopt and are greater than R20 arc transition.

Because the making method of high-strength prestress bolt of the present invention have employed technique scheme, namely present method adopts vacuum induction and electroslag heavily to melt technique smelting medium carbon alloy steel, and controls foreign matter content; Employing vacuum oven is heat-treated, and quenching temperature is 860 DEG C, and one time high tempering temperature is 560 DEG C, and secondary high-temperature tempering temperature is 500 DEG C; Carry out machining according to required bolt specification, screw thread adopts accurate digital control rolled thread processing, and central diameter allowance control is within 0.1mm, and list of bolts surface roughness and screw thread roughness are Ra0.8, and all transit sites of bolt adopt and are greater than R20 arc transition.The bolt that present method makes has the advantage of high strength, high tenacity, and its mechanics properties testing index meets bears the fastening of larger repeated load parts, guarantees the safe and reliable operation of these parts, and reduces cost of manufacture and cycle.

Embodiment

The making method of high-strength prestress bolt of the present invention comprises the steps:

Step one, employing vacuum induction and electroslag heavily melt technique smelts medium carbon alloy steel, its elemental composition is C content 0.28-0.32wt%, Si content 0.20-0.30wt%, Mn content 0.45-0.55wt%, Cr content 2.7-3.2wt%, Ni content 2.8-3.5wt%, Mo content 0.55-0.65wt%, control P, S, H, O foreign matter content in medium carbon alloy steel, P content≤0.015wt%, S content≤0.005wt%, H content≤2ppm, O content≤20ppm, N content≤60ppm, reduce the impelling strength of impurity on medium carbon alloy steel and the impact of fatigue strength; Control C content and can obtain higher toughness between 0.28-0.32wt%, alloying elements cr, Mn, Ni etc. can increase the hardening capacity of steel, and the ratio of Ni and manganese is more conducive to the impelling strength improving steel; The impelling strength harm of impurity P alloy steel is very large, and the Fatigue Strength Effect of O content to steel is huge, and H content great Yi produces white point and hydrogen embrittlement, therefore does strict control to foreign matter content;

Step 2, employing vacuum oven are heat-treated the medium carbon alloy steel after smelting, preheating 650 DEG C, insulation 160min, 80 DEG C/h is warming up to 860 DEG C, and insulation 130min, 80 DEG C/h are cooled to first time tempering 560 DEG C, insulation 420min, be cooled to second time tempering 500 DEG C, insulation 360min, air cooling is to room temperature;

Step 3, according to required bolt specification, machining is carried out to the medium carbon alloy steel after thermal treatment, screw thread adopts accurate digital control rolled thread processing, central diameter allowance control is within 0.1mm, list of bolts surface roughness and screw thread roughness are Ra0.8, and all transit sites of bolt adopt and are greater than R20 arc transition.

Present method take medium carbon alloy steel as raw material, heavily melt technique through vacuum induction and electroslag and reduce wherein impurity, the martensitic stucture of enough degree of depth and quantity and good comprehensive mechanical property is obtained after vacuum oven thermal treatment, make the bolt adopting medium carbon alloy steel to make have the advantage of high strength (Rp0.2 > 1080MPa) and high tenacity (Aku > 80J), performance index are equal to and are even better than foreign same type high-strength prestress bolt.Not only greatly reduce the cost of manufacture of bolt, shorten fabrication cycle, also greatly reduce the dependency to import spare part simultaneously.

Claims (1)

1. a making method for high-strength prestress bolt, is characterized in that present method comprises the steps:

Step one, employing vacuum induction and electroslag heavily melt technique smelts medium carbon alloy steel, its elemental composition is C content 0.28-0.32wt%, Si content 0.20-0.30wt%, Mn content 0.45-0.55wt%, Cr content 2.7-3.2wt%, Ni content 2.8-3.5wt%, Mo content 0.55-0.65wt%, control P, S, H, O foreign matter content in medium carbon alloy steel, P content≤0.015wt%, S content≤0.005wt%, H content≤2ppm, O content≤20ppm, N content≤60ppm, reduce the impelling strength of impurity on medium carbon alloy steel and the impact of fatigue strength;

Step 2, employing vacuum oven are heat-treated the medium carbon alloy steel after smelting, preheating 650 DEG C, insulation 160min, 80 DEG C/h is warming up to 860 DEG C, and insulation 130min, 80 DEG C/h are cooled to first time tempering 560 DEG C, insulation 420min, be cooled to second time tempering 500 DEG C, insulation 360min, air cooling is to room temperature;

Step 3, according to required bolt specification, machining is carried out to the medium carbon alloy steel after thermal treatment, screw thread adopts accurate digital control rolled thread processing, central diameter allowance control is within 0.1mm, list of bolts surface roughness and screw thread roughness are Ra0.8, and all transit sites of bolt adopt and are greater than R20 arc transition.