Screw material and process

Screw material and process

Date:2022-01-17
With the ever-changing engineering plastics, the use of high glass fiber and acid flame retardants, the traditional nitriding and PTA double alloy screws have been unable to meet the requirements of service life, in order to meet the requirements of long-term use in high wear and high corrosion conditions , Need more high wear resistance, high corrosion resistance, high toughness, high red hardness of the screw.
According to the different steel materials and processes, it can be roughly divided into nitrogen screw, PTA double alloy screw, fully covered screw, fully hard screw, and sintered screw. However, the names of each manufacturer will be somewhat inconsistent. For example, Tianxingjiang (PTA double alloy screw, fully covered screw, fully hard screw) is called double alloy screw.
Fully hardened screw
Generally use tool steel, die steel, stainless steel, powder steel, etc.
The Kotler full-hard screw is manufactured after heat treatment, the screw teeth are ground and formed by a CNC screw grinder, and the tail keyway is made of CNC.
Contains Cr, V, W, Mo, etc., which greatly improves the wear resistance and corrosion resistance of the screw
Due to the huge difference in the materials used for full-hard screws, there are great differences in life, applicable working conditions and prices. The more common materials are SKD61, DC53, SKH-9, etc.
Restricted by domestic metallurgical technology, domestic steel cannot compete with imported steel. At present, Kotler's screws are all imported from Japan and Europe. And some of the materials are the first to be imported in China
The production process of fully hardened screw:
Process 1, heat treatment after processing the thread; low processing requirements and easy processing. However, the screw is prone to deformation during heat treatment. In order to ensure the straightness of the screw, during the screw calibration process, high temperature leads to annealing, which affects the hardness. Affected by technology, equipment, cost, etc., this process is generally adopted in China.
Process 2: Process the thread after heat treatment; the hardness of the round bar reaches 50-65 degrees after heat treatment, and it is necessary to use higher hardness tools (such as CBN) and grinding (screw grinding equipment still relies on imports), foreign and a few domestic manufacturers use this process .
Main steel:
Tool steel, which contains a large proportion of medium Cr, V, W, Mo, has good wear resistance and certain corrosion resistance, and has high toughness and good red hardness
Stainless steel, which contains a large amount of chromium to excel in corrosion resistance tests
Powder steel, manufactured by powder metallurgy, with fine carbides and uniform distribution. In the test of corrosion resistance and wear resistance, the indicators far exceed tool steel