Manufacturing process for bolt with high strength of more than phi 30

A high-strength bolt and manufacturing process technology, used in the manufacture of tools, bolts, threaded fasteners, etc., can solve the problems of long heating time, high temperature, and easy formation of oxide layers on bolts, so as to refine grains and avoid crystallites. coarse grain effect

Inactive Publication Date: 2011-11-23
浙江迪特高强度螺栓有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In this method, the heat preservation temperature is relatively high and the heating time is long, which will consume more electric energy and cost more
Second, because this method adopts normalizing treatment, the temperature is high, and the cooling method is air, so the surface of the bolt is easy to form an oxide layer, which affects the appearance and size of the

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0019] 42CrMo steel is selected as the raw material. According to the wire diameter requirements of the bolt, the raw material is pretreated and then heated forging. The heating forging temperature is 1100 ° C, and the heating forging time is 5 minutes. After heating forging, the corners of the high-strength bolt head of the present invention The hardness is HRC45, and the metallographic structure is martensite. The workpiece after heating and forging is quickly sent to the mesh belt furnace for high temperature tempering. After the workpiece enters the mesh belt furnace, it first passes through the preheating zone of the mesh belt furnace. Preheat at the temperature for 30 minutes, then enter the first heating zone and the second heating zone, heat at 570°C for 30 minutes after entering the first heating zone, then enter the second heating zone, heat at 570°C 30 minutes, and finally enter the heat preservation zone for heat preservation, at 570 ° C for 60 minutes.

[0020] Ta...

Embodiment 2

[0022] 42CrMo steel is selected as the raw material. According to the requirements of the wire diameter of the bolt, the raw material is pretreated and then heated forging. The heating forging temperature is 1200°C, and the heating forging time is 3 minutes. The hardness is HRC50, and the metallographic structure is martensite. The workpiece after heating and forging is quickly sent to the mesh belt furnace for high temperature tempering. After the workpiece enters the mesh belt furnace, it first passes through the preheating zone of the mesh belt furnace. Preheat at the temperature for 30 minutes, then enter the first heating zone and the second heating zone, heat at 560°C for 35 minutes after entering the first heating zone, then enter the second heating zone, heat at 560°C 30 minutes, and finally enter the heat preservation zone for heat preservation, at 560°C for 70 minutes.

[0023] Take out the workpiece after high temperature tempering and cool it with water. The metall...

Embodiment 3

[0025] 42CrMo steel is selected as the raw material. According to the requirements of the wire diameter of the bolt, the raw material is pretreated and then heated forging. The heating forging temperature is 1300°C, and the heating forging time is 2 minutes. The hardness is HRC55, and the metallographic structure is martensite. The workpiece after heating and forging is quickly sent to the mesh belt furnace for high temperature tempering. Preheat at the temperature for 40 minutes, enter the first heating zone and heat at 550°C for 40 minutes, then enter the second heating zone, heat at 550°C for 40 minutes, and finally enter the holding zone for heat preservation, at 550°C C for 80 minutes.

[0026] Take out the workpiece after high-temperature tempering, and cool it with water. The metallographic structure of the workpiece after tempering is pearlite and ferrite. The hardness of the workpiece is tested. The surface hardness of the workpiece after tempering is HRC35. The work...

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PUM

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Abstract

The invention discloses a manufacturing process for a bolt with high strength of more than phi 30. The manufacturing process comprises the following steps of: forging; performing heat treatment and after treatment, wherein the heating forging temperature is between 1,100 and 1,300 DEG C, and the heating forging time is between 2 and 5 minutes; directly feeding workpieces into a mesh belt furnace quickly after forging for high temperature tempering, wherein the mesh belt furnace comprises a preheating area, a first heating area, a second heating area and a heat preservation area; preheating the workpieces through the preheating area after the workpieces are fed into the mesh belt furnace, and heating the workpieces through the first heating area and the second heating area; preserving the heat through the heat preservation area; cooling the workpieces which are subjected to the high temperature tempering; and trimming the cooled workpieces. By the manufacturing process, the workpieces are directly fed into the mesh belt furnace for high temperature tempering after being heated and forged, the excess heat of the forged workpieces is fully used, and time and energy are saved. The workpieces have a tempered sorbite structure after the high temperature tempering, grains are refined, and the phenomena that the grains are coarse and a martensite structure and a raw material structure are blended are prevented.

Description

technical field [0001] The invention relates to material forging and heat treatment technology, in particular to a forging and heat treatment process for high-strength bolts with diameters above Φ30. Background technique [0002] High-strength bolts are bolts that require a large pre-tightening force, and are mostly used for the connection of bridges, rails, high-pressure and ultra-high-pressure equipment. High-strength bolts require a strong bearing capacity when used, and the raw materials used have high strength, so they have high requirements for processing technology. [0003] High-strength bolts above Φ30 cannot be formed by cold heading due to their special requirements, and must be forged by heating. After forging, redundant edges will be formed on the head and need to be cut off. During the heating forging process of high-strength bolts, the heating forging temperature is relatively high, and the product after forging needs to be cooled for a long time. Due to the...

Claims

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Application Information

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IPC IPC(8): B21K1/44B21J5/00C21D9/00C21D1/25
Inventor 苏友份藤宝贵周世团
Owner 浙江迪特高强度螺栓有限公司
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