Duplex stainless steel in the United States since the birth of 1940s, has been developed to the third generation. Its main feature is the yield strength of up to 400-550MPa, is 2 times of ordinary stainless steel, so it can save material, reduce the cost of equipment manufacturing. In corrosion resistance, especially in the media environment is bad (such as water, chlorine ion content is higher) under the condition of double phase stainless steel pitting corrosion, crevice corrosion, stress corrosion and corrosion fatigue performance is obviously better than ordinary austenitic stainless steel, high alloy austenitic stainless steel can be comparable with.