Abstract: The specimen of the S32250 duplex stainless steel pipe as cracked during the piercing process is analyzed. As a result it is revealed that under the same piercing process conditions,the less ferrite content,the greater the piercing-caused cracking rate will be. With the induction method,it is confirmed that the hot-workability of the S32205 steel is associated with the residual element Cu. Along with increase of the Cu content,the σ phase precipitation temperature remains the same,while the Cr₂N precipitation temperature goes up. Meanwhile the optimum thermoplastic point 40%A temperature goes up too. And after the Cu content exceeds 0.2%,the optimum thermoplastic range(40%A~Cr₂N) is obviously reduced. Therefore it is concluded that provided that the residual element Cu in the S32205 duplex stainless steel is well controlled to be within the range of 0.2%,its optimum hot-workability will be obtained.