PRODUCTION METHOD OF STAINLESS STEEL TUBE

• Main Authors: TOMIO YUSAKU, OTOME YOHEI
• Format: Patent
• Language: English; Japanese
• Published: 08.03.2018
• Subjects: ALLOYS; CHEMISTRY; FERROUS OR NON-FERROUS ALLOYS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; TREATMENT OF ALLOYS OR NON-FERROUS METALS

PROBLEM TO BE SOLVED: To provide a production method of a stainless steel tube containing Cr of 11.0 to less than 15.5% and having excellent toughness even having large size and thick wall.SOLUTION: The production method includes a step of hot working a steel material containing, by mass%, C:0.05% or less, Si:1.0% or less, Mn:0.05 to 2.0%, P:0.05% or less, S:0.005% or less, Cr:11.0 to less than 15.5%, Ni:4.5 to 8.0%, Mo:1.5 to 3.5%, Al:0.001 to 0.1%, N:0.001 to 0.10%, O:0.01% or less and the balance Fe with impurities to produce a tube stock having an outer diameter of 175 mm or more and a wall thickness of 10 mm or more, a step of hardening the tube stock at 800 to 1000°C, and a step of tempering the hardened tube stock, the tempering step has a step of holding the tube stock at 500 to 650°C and a step of cooling the held tube stock, the average cooling rate in a temperature range of 500 to 400°C being set to be 10°C/min. or more.SELECTED DRAWING: Figure 1 【課題】１１．０〜１５．５％未満のＣｒを含有し、大型及び厚肉であっても優れた靭性を有するステンレス鋼管の製造方法を提供する。【解決手段】上記製造方法は、質量％で、Ｃ：０．０５％以下、Ｓｉ：１．０％以下、Ｍｎ：０．０５〜２．０％、Ｐ：０．０５％以下、Ｓ：０．００５％以下、Ｃｒ：１１．０〜１５．５％未満、Ｎｉ：４．５〜８．０％、Ｍｏ：１．５〜３．５％、Ａｌ：０．００１〜０．１％、Ｎ：０．００１〜０．１０％、及びＯ：０．０１％以下を含有し、残部はＦｅ及び不純物からなる鋼材を熱間加工し、外径１７５ｍｍ以上かつ肉厚１０ｍｍ以上の素管とする工程と、素管を８００〜１０００℃から焼入れする工程と、焼入れ後の素管を焼戻しする工程とを備え、焼戻しする工程は素管を５００〜６５０℃で保持する工程と、保持後の素管を冷却し、素管温度が５００〜４００℃の温度域における平均冷却速度を１０℃／ｍｉｎ以上とする工程とを含む。【選択図】図１