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1.
Sulfur forms MnS inclusions with Mn in steel, which can interrupt the continuity of the matrix, make the chip brittle, reduce the contact area between the chip and the tool, and also play a role in reducing friction, so that the chip does not adhere to the cutting edge. However, the presence of sulfur will cause hot brittleness of steel, so the sulfur content should be generally limited to the range of w (s){{0}}.10 percent ~0.30 percent , and the content of Mn should be appropriately increased to match with it.
2.
The addition of Pb can improve the cutting performance of steel. As Pb does not dissolve into ferrite or form compounds in steel, it forms fine particles (2~3 μ m) It is evenly distributed in the matrix structure. When the heat generated in the cutting process reaches the melting point of Pb particles, it is in a melting state and becomes the "lubricant" between the tool and the chip as well as between the tool and the machined surface of the workpiece, reducing the friction coefficient, tool temperature and wear. The amount of Pb added is within the range of w (Pb)=0.1 percent - 0.35 percent .
3. Effect of Calcium(Ca)
Ca can form silicate inclusions of Ca and Al in steel, which can attach to the tool to form a film, which has the function of reducing friction and preventing tool wear. The addition amount of Ca is generally w (Ca)=0.001 percent - 0.005 percent .
4.
P is added to the sulfur free cutting steel to make it solid soluble in ferrite, resulting in strengthening and embrittlement, so as to improve its cutting performance. To prevent "cold brittleness", w (P) Less than or equal to 0.15 percent is specified.
