Spheroidizing annealing process of superplastic medium carbon steel wire

Abstract

The invention discloses a spheroidizing annealing process of a superplastic medium carbon steel wire. The spheroidizing annealing process comprises the following steps of placing a steel wire into a thermal treatment furnace, charging protective gas into the thermal treatment furnace, raising the temperature inside the furnace to 720-740 DEG C, and preserving the heat for 3-5 hours; cooling at the first stage, namely reducing the temperature inside the furnace to 660-680 DEG C at the speed of 10 DEG C / h, and preserving the heat for 3-5 hours; cooling at the second stage, namely further reducing the temperature inside the furnace to 610-630 DEG C at the speed of 20 DEG C / h; and cooling at the third stage, namely naturally cooling the steel wire to the normal temperature. The steel wire treated by using the process disclosed by the invention is uniform in metallographic structure, high in plasticity and ductility, suitable for subsequent repeated high-difficulty plastic processing and molding and low in molding cracking rate.

Description

Technical field: [0001] The invention relates to an annealing process of metal materials, in particular to a spheroidizing annealing process of superplastic medium carbon steel wire. Background technique: [0002] Spheroidizing annealing is one of the basic ways to improve the structure and properties of steel. The main purpose of spheroidizing annealing is to spheroidize carbides in the microstructure of steel materials, reduce the hardness of materials, improve the plasticity of materials, and reduce the deformation resistance of materials. , making the material easy to plastic processing. In order to obtain ideal properties and microstructure in the production of superplastic medium carbon steel wire, the key is to choose an appropriate spheroidizing annealing process. [0003] At present, the market has high requirements on the cold heading performance of medium carbon steel. Because of the high carbon content of medium carbon steel, the current traditional spheroidizi...

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Problems solved by technology

[0003]At present, the cold heading performance of medium carbon steel is high in the market. Because of the high carbon content of medium carbon steel, the current traditional spheroidizing process is difficult to meet the needs of customers. A Chinese patent discloses an annealing process for medium carbon steel, the patent number of which is 201210313297.8. The process adopted is to increase the internal stress of the wire in advance, adopt pre-vacuumization, and fill the atmosphere with nitrogen to protect the atmosphere. The cooling rate is less than 50°C / h, the temperature is kept at 720°C for 5 hours, and the furnace is air-cooled to 300°C. The final metallographic structure of this process is F+P balls, and the grade is 4-6. The metallographic structure is uneven and the hardness is partial. High, poor toughness, it is difficult to meet the needs of customers for the current cold-formed large deformation products, a large number of medium-carbon steel wires have cracks after cold-forming, and the severe ones directly cause the production of medium-carbon steel wires to break and be scrapped, which seriously affects the quality and quality of medium-carbon steel wires. Yield