We know that although all stainless steels can be processed, just as they have great differences in physical and chemical properties, there are also great differences in processing properties.
Stainless steel generally refers to iron-based alloys with a chromium content of more than 11.5%. In order to obtain ideal corrosion resistance or special mechanical properties, carbon, nickel, manganese, molybdenum, titanium, niobium and other alloying elements are often added. Sometimes, sulfur, selenium, and sulfur aluminum compounds are also added. Since these elements have the properties of metal inclusions, they can promote the improvement of machining performance.
Hardenable martensitic steel can usually be quenched to increase its hardness, and the degree of difficulty of processing depends on the carbon content of the steel. The higher the carbon content, the more difficult it is to process. The 2Cr13, 3Cr13 and 1Cr17Ni2 commonly used in the valve industry are all common processing types.
Martensitic steel in the annealed state is magnetic, and the required strength and hardness can be obtained by quenching and quenching and tempering.
The hardness of ferritic steel cannot be significantly changed by heat treatment. Since the structure of this type of steel is ferrite, it is magnetic in the annealed state. Currently, this type of steel is not widely used in the valve industry.
Austenitic stainless steels are non-magnetic in the annealed state and cannot be hardened by heat treatment, but most of them have a tendency to work hardening. This tendency is much more pronounced for austenitic steels than for martensitic steels and ferritic steels. In terms of processing performance, austenitic steel is worse than the other two types of steel. This is because this type of steel is sticky in the annealed state and has a tendency to harden quickly during processing.
The austenitic steel commonly used in the valve industry, such as 1Cr18Ni9Ti, 1Cr18Ni11Nb, 1Cr18Ni12Mo2Ti, OCr18Ni9, OOCr18N10, OOCr17Ni14Mo2, 1Cr18Ni9, etc., are all ordinary processing types.
The machine tools used for processing stainless steel parts are basically the same as those used for processing carbon steel. However, from the perspective of the difficult-to-cut characteristics of stainless steel, the following issues should be paid special attention to:
(1) Requirements for machine tools. Since stainless steel is difficult to cut, and the cutting process consumes more power, the actual load of the machine tool is preferably less than or equal to 75% of the rated capacity. In addition, the machine tool should have sufficient rigidity to avoid vibration and deformation during the cutting process.
(2) Requirements for cutting tools. When machining stainless steel, due to the relatively large cutting force, the tool must have sufficient strength and rigidity, the cantilever of the tool should be short, the tool should be clamped before cutting, and additional clamping can be added if necessary.
The cutting material of the tool generally has two kinds of high-speed steel and cemented carbide. No matter what material is used, the blade should be kept sharp at all times. It is best to sharpen it regularly instead of waiting until it is dull.
(3) A good lubricant should be used for stainless steel processing.
(4) Do everything possible to use strong cutting, especially when cutting chromium-nickel austenitic stainless steel, to avoid work hardening and slipping.