What are the requirements for the quality of the screw

Update:29 Mar 2019
Summary:

1 The screw for the extruder should be made of alloy st […]

1 The screw for the extruder should be made of alloy steel which is heat-deformed, wear-resistant and corrosion-resistant. Commonly used materials are 38CrMoAlA alloy steel or 40Cr steel, and repair parts can also be made of 45 steel.
2 Screw blanks should be formed by forging.
3 After the screw is machined, the accuracy of the outer circle should reach the accuracy and quality requirements of 8 (GB 180-79).
4 The error of the coaxiality between the working shaft surface of the screw and the connecting part of the transmission shaft and the outer circumference of the thread of the screw should be no more than 0.01mm.
5 screw thread part working surface roughness R. Value: The two sides of the thread should be no more than 1.69m, and the thread bottom and outer circle should be no more than 0.8/1m.
6 If the screw is made of low carbon alloy steel material, in order to improve the hardness and corrosion resistance and wear resistance of the thread working surface, the thread surface should be nitrided, the nitride layer depth is 0.3-0.6 ram, and the surface hardness is 700-840 HV. The brittleness is not more than 2 grades.
7 The screw inner hole joint should be tested with 0.3MPa hydraulic pressure, and no leakage is allowed for 5min.

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