Compared with the austenitic stainless steel plate represented by SUS430(16%Cr) iron system rust steel plate and SUS304(18%Cr-8%Ni) austenitic stainless steel plate, although the price is cheap, but the corrosion resistance is poor, and the processability is low. However, recently JFE443CT(21%Cr-0.4%Cu-0.3%Ti) iron system steel plate with corrosion resistance similar to SUS304 is being popularized in many application fields, especially in the case of high nickel price, its cost reduction effect is significant. However, it is sometimes difficult to use the original austenitic materials to process the parts with the original tools and processes to use the ferrite materials such as JFE443CT. This is due to the difference in the essential crystal structure of the two machining characteristics, especially the difference in ductility. Although JFE443CT is an improvement over SUS430, it is still significantly different from SUS304. However, there is no need to give up the low cost characteristics of ferritic system materials due to processing problems. As long as the basic processing characteristics of the material are studied deeply, the proper processing method is selected and the parts are designed according to the situation, the complex forming process of iron system materials such as JFE443CT can be carried out.
According to the stress-strain curves of the two steels obtained from the uniaxial tensile test above, it can be seen that the initial yield stress of JFE443CT has a high tendency, and the stress-strain curves of the two steels cross in the range of strain less than 0.1.
(1) Characteristics of deep drawing and protruding belly. The results of LDR test show that JFE443CT has higher processing limit than SUS304. This is because the degree of work hardening of the former is small, the R value is high, and the deep punching resistance of the flange is small compared with the longitudinal wall strength.
The results of ball bottom bump test by cup bump test show that in such simple bump processing, the machinability is basically determined by the ductility value of materials. As the elongation of JFE443CT is only about 1/2 that of SUS304. Therefore, the processing of the former convex abdomen is poor.
It can be seen from the test results of cone die cup protrusion of the two steels that the composite formability of deep drawing and convex belly is basically the same.
(2) Bonding bending characteristics. After 180° bonding bending test was carried out on 2B sheet of 1.5mm thickness of two kinds of steel, the observation results of the bending section showed that both JFE443CT and SUS304 could bend 180° without any problem. But in strict bending occasions, JFE443CT material will sometimes produce small wrinkles on the outer surface and make the surface rough (whitening), and even the phenomenon of inner surface folding. This is because its grain diameter is larger than SUS304, easy to produce uneven wrinkling on the free surface, and because of the small work hardening and easy to concentrate the strain. But because the work hardening of the developed steel is small, its compact degree is generally good.
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