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

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...

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 bolt and affects the use.

In addition, the air cooling method of this method is generally an open air cooling method, and the surface temperature of the bolts is high, and the cooling will be relatively slow, so that the surface temperature around the bolts is high, and the temperature around the bolts will be high, resulting in labor intensity for workers. also high