| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing seamless tube of martensitic stainless steel having high strength and high toughness in the range 95 (655)-125 ksi (861 MPa) in yield strength. SOLUTION: In the method for manufacturing the seamless tube of martensitic stainless steel, a base stock of 13 Cr martensitic stainless steel is hearted to the austenitic region and a tube stock is produced by applying piecing and drawing as the hot finish rolling. Then hot finish rolling is applied where the relationship between the rolling starting temperature TR of the tube stock and the reduction RA in an area of the hot finish rolling satisfies a specified relation in accordance with desired strength. After completing the hot finish rolling, the structure is made into martensitic structure by cooling the tube stock to the room temperature, and also temper treatment for satisfying a temper parameter TP in accordance with the desired strength is performed. In this way, the seamless tube of martensitic stainless steel which has both of the high strength in the range of 95 (655)-125 ksi (861 MPa) and the high toughness of >=30 J at -40 deg.C is produced.
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