As a free-cutting element, it first appeared in the patent of 1932. 196 1 year, the United States successfully developed a tellurium-containing free-cutting steel, which is a multi-component composite free-cutting steel of sulfur, lead and tellurium. Its cutting performance is excellent, comparable to that of free-cutting brass. Selenium and tellurium are often used alternately or added to steel at the same time because of their similar properties and functions.
Calcium deoxidation
Since the 1960s, people have studied another method to improve the machinability of steel, that is, adding a certain deoxidizing element to generate the required deoxidizing product-favorable inclusions, which is called deoxidizing adjustable free-cutting steel in Japan. 1964, the former federal Republic of Germany first filed a patent for calcium deoxidized calcium free-cutting steel, which was introduced and officially produced in Japan three years later. It is most suitable for high-speed cutting with TiC cemented carbide tool, which can significantly improve productivity and reduce tool consumption. In Japan, it has become a kind of free-cutting steel widely used in automobile and tractor manufacturing.
Titanium deoxidation
Since the late 1960s, people have been studying the free-cutting steel deoxidized by titanium. 1973, Japan first published the patent of titanium deoxidized titanium-sulfur composite free-cutting steel, and in recent years, it has been tried in a few countries such as Japan.