Cold heading hex bolt secondary reduction process: Applicable machine tools: four-station cold heading machine
Cold Drawn Steel Bar is produced by hot rolled steel bar or wire rod to get smooth surface, more precision size, higher mechanical properties, which improves machining characteristics. It can also get various sections and sizes. So cold drawn steel bar is a better choice for machining users.
According to different steel grade, the production line is usually different. The Basic production line is as below:
For high carbon steel or alloy steel bars, to avoid the cracks in inner or surface, the bars are usually required to be annealed before cold drawing.
To get different mechanical properties or hardness depending on final usage, the cold drawn bars will also be heat treated such as annealed, normalized or quenched and tempered(Q&T).
For CNC machines usage, to get much more precision sizes or much more better surface roughness for chrome plating, the cold drawn steel bars can also be centerless ground or polished.
We have more advantages on producing cold drawn steel bars:
1) Big stocks of hot rolled round bars or wire rods as raw materials
2) Wide range of cold drawn steel bar sizes: from 10mm to 150mm
3) Different cold drawing medias powder or oil to get different surface
4) Straightening machines to get better straightness up to 0.5mm/m
5) Grinding and polishing machines to get better roughness upto 0.4um
6) Heat treating furnaces to adjust the mechanical properties
7) Full sets of testing equipment to test the sizes, mechanical properties and microstructure.
8) Multiple packages to avoid broken packages and anti-rusty
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Blank: blank diameter d0≈(1.14～1.18)d(d=rod diameter)
Process: First station: full length reduction of the rod
Second station: pre-clamping the cylindrical head and forming the rod end chamfer
Third station: complete hexagonal trimming
The fourth station: the final hex head with the washer face, and the second reduction of the diameter of the rod, so that it reaches the diameter of the spiral required for the filature
Features: This process uses secondary reduction 
