In an annealed condition, the relative machinability of austenitic grades ss machined washer is around 50 as compared to carbon steels, whose relative machinability is 100. This difference is observed due to the nature of stainless steels being tough rather than hard. Which is why stainless steel has a tendency to seize and gall.
Three of the most commonly machined stainless steel grades are 202, 304 & 316. All the three grades, i.e. – 202, 316 & 304 are austenitic grades of stainless steel. The difference between these stainless steel grades is due to the change in composition. For instance, the 202 grade stainless steel machine washers primarily contains chromium, manganese & nickel as their alloying materials. While the both the grades 304 & 316 tend to have both chromium as well as nickel predominantly in their alloys.
During the machining of grade 202 stainless steel, long, gummy chips are produced. Machining of stainless steel grade 202 can also be performed in the annealed condition. The heat treatment is done to the material by soaking it at 1038°C for 30 min, followed by cooling below 16°C for full martensite transformation. Although the material can be welded by using common fusion and resistance methods, this steel grade should not be joined using oxyacetylene welding technique. The recommended filler metal for this alloy is AWS E/ER630. Forging of the ss 202 machined washer can be done by pre-soaking for the alloy for 1 hour at 1177°C. Forging the alloy below a temperature of 1010°C is not advisable.
Alloy 304 or 304H or 304L are subject to work hardening during deformation. This ss 304 machined washer is subjected to chip breaking during machining. The best machining results are observed when the a combination of slower speeds, excellent lubrication, heavier feeds, sharp tooling and powerful rigid equipment are used to machine this grade.Besides being a very popular alloy, the 316 has a machining cost factor of 5.6 when compared to carbon steel grade12L14. ss 316 machined washer is recommended for welding as grade 316 can be readily cold worked.
