Technology for processing high strength large hexagon-headed bolt used for steel structure

Abstract

The invention provides a technology for processing high strength large hexagon-headed bolt used for steel structure. The invention relates to a technology for processing high strength connecting piece. High frequency induction current hot forging and cold extruding are adopted, so as to produce a bolt. The invention is on the basis of patent application with patent application number of 200810020090.5, high frequency induction heating is adopted in hot forging, frequency thereof is controlled to be 20000-50000Hz, and the advantages of high frequency induction heating that speed is fast and heating is uniform are utilized, so that work piece surface can obtain uniform tissue and properties from center part to the surface, heating uniformity of work piece is improved, better crystal phase structure can be obtained, and high strength bolt with better property can be obtained.

Description

technical field [0001] The invention relates to a processing technology of a high-strength connecting piece, in particular to a processing technology of a high-strength large hexagon head bolt for a steel structure. Background technique [0002] High-strength large hexagon head bolts for steel structures are commonly used fasteners in the machinery industry. The current processing method is generally formed by turning, and its strength is often difficult to guarantee. When the tensile strength exceeds a certain value, in the places where the gaps are concentrated For example, the transition between the rod and the head or the root of the thread is likely to cause delayed fracture and fatigue fracture, which will seriously affect the quality of the project. In severe cases, it will cause safety accidents due to insufficient connection strength. Therefore, traditional high-strength bolts need to be replaced. Research and improve the production process, in order to efficiently ...

AI Technical Summary

Problems solved by technology

[0002] High-strength large hexagon head bolts for steel structures are commonly used fasteners in the machinery industry. The current processing method is generally formed by turning, and its strength is often difficult to guarantee. When the tensile strength exceeds a certain value, in the places where the gaps are concentrated For example, the transition between the rod and the head or the root of the thread is likely to cause delayed fracture and fatigue fracture, which will seriously affect the quality of the project. In severe cases, it will cause safety accidents due to insufficient connection strength. Therefore, traditional high-strength bolts need to be replaced. Research and improve the production process, in order to efficiently carry out mass production under the premise of ensuring its quality, and meet the society's extensive needs for high-strength large hexagon head bolts for steel structures. Therefore, the patent application No. 200810020090.5 provides A processing technology for high-strength large hexagon head bolts for steel structures is proposed. The main invention lies in the use of less cutting technology and cold extrusion processing to improve the axial surface or internal fiber structure of the workpiece. At the same time, heat treatment uses Salt bath quenching and nitrate tempering reduce the degree of oxidation and decarburization on the surface of the workpiece and further ensure the quality of the bolts. However, in the step of hot forging, heating with a hot forging furnace has slow heating speed and uneven heating. , causing some parts of the workpiece to be overheated and some places to be underheated, which may easily cause defects such as skinning, slag inclusion, cracking, and cracking on the workpiece, and further improvement is needed