Free cutting steel SUM21 round steel cold drawn SUM25 round bar cutting steel bar

SUM21 free cutting steel use: Often used in the manufacture of unimportant standard parts, such as bolts, nuts, pipe joints, spring seats, etc.

SUM21 is a free cutting structural steel, free cutting steel is easy to be (turning, milling, drawing, planing, drilling, etc.) cutting steel, also called from

Steel for machine tool processing, referred to as automatic steel. It is produced to adapt to machining automation and assembly line production. This kind of steel can be cut with a higher cutting speed and a deeper cutting amount, and due to the addition of the cutting element in the steel to reduce the cutting resistance and due to the characteristics of the addition of the element itself and the formation of the compound play the role of lubricating the tool edge, so that the chip is easy to break, reduce the wear, so that the finish and accuracy of the machined parts, the tool life and production efficiency.

Chemical composition:

Carbon C: 0.13

Manganese Mn: 0.70 ~ 1.00

P: 0.07 ~ 0.12

Sulfur S: 0.16 ~ 0.23

● Mechanical properties:

Tensile strength σb (MPa) : (hot rolled)390 ~ 540; (cold drawn) steel thickness or diameter 8 ~ 20 :530 ~ 755; >20 ~ 30 hours :510 ~ 735; >30 hours :490 ~ 685

Elongation δ5 (%) : (hot rolling)≥22; (Cold rolled)≥7.0

Section shrinkage (%) : (hot rolling)≥36

Hardness: (hot rolling)≤170HB; (cold drawn) 152-217HB

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