Thread rolling dies is a special tool for processing taps and bolts. It is the most commonly used thread making tool for processing screws and bolts in the standard fastener industry. The processing principle mainly adopts cold extrusion. Cold extrusion has the advantages of high production efficiency, low processing cost, high thread precision and strength, good surface quality and so on.
Thread rolling dies are generally formed by cold rolling. They are not processed after heat treatment. During operation, the tooth shall bear severe impact load and extrusion stress. After heat treatment, the hardness within 3 to 5mm below the tooth root is 58 to 61hrc, the quenched martensite is less than grade 3, and there is no decarburization on the tooth surface.
Thread rolling dies should have high hardness, wear resistance, sufficient strength, certain impact force and strong fatigue resistance. It is made of 9SiCr and Cr12MoV steel. The hardness of the working part is 59 ~ 62Hrc. If it is > 62Hrc, it is easy to collapse and if it is < 59HRC, it is easy to wear; Quenched martensite < grade 3; The working surface shall be free of decarburization and low hardness; The surface of the wire take-up plate shall be free of cracks, nicks, rust, grinding burns and other defects affecting the service performance.
The materials selected for thread rolling dies shall have the following properties:
Good hardenability, high matrix hardness and good wear resistance;
Good dimensional stability;
Good impact toughness and appropriate strength;
Good machinability and hot machinability.
Therefore, the common materials suitable for manufacturing are 9SiCr, Cr12 or Cr12MoV, but most factories use 9SiCr at present.
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