Precautions for ferritic stainless steel seamless pipe and tube

  • Huzhou Nanxun Yintuo Special Material Technology Co., Ltd. specializes in the development and production of high-quality stainless steel seamless tubes and nickel-nickel alloys. Now let’s introduce ferritic stainless steel seamless pipe and tube.

    (1) 475"C brittleness problem. If ferritic stainless steel containing more than 12% chromium is heated to above 340C, especially in the range of 400~500C, the toughness of the steel will be significantly reduced and become brittle. This kind of The embrittlement phenomenon is the most serious at a temperature of about 475"C, so it is called 475"C brittleness. The higher the chromium content, the shorter the time required to produce this brittleness. 475°C brittleness can be achieved by heating the steel to 600°C The above temperature is then quickly cooled to room temperature to eliminate it. The higher the temperature, the easier it is to eliminate brittleness, usually between 700~800C.

    (2) The problem of high temperature brittleness. High chromium ferritic stainless steel containing a considerable amount of interstitial elements (C, N, etc.), heated to 950'C or above 950°C, and then rapidly cooled, can greatly reduce the toughness and plasticity of the steel at room temperature, resulting in obvious brittleness. This phenomenon is called high temperature brittleness. This brittleness phenomenon often occurs in castings, welded parts, and workpieces that are heated above 950°C.

    The high temperature brittleness of ferritic stainless steel can be eliminated by heating the steel to 750~850°C and then quenching it, and the plasticity of the steel can be restored.

    (3) Sensitization problem. Like austenitic stainless steel, ferritic stainless steel will also be sensitized after a certain heat treatment and will be sensitive to intergranular corrosion. Moreover, compared with Cr-Ni austenitic stainless steel with the same amount of C and Cr, it is more prone to sensitization, that is, it has a higher sensitivity to intergranular corrosion. The sensitization temperature of ferritic stainless steel is above 925C, such as the fusion line of welded joints.

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