FOSHAN FEROSTEEL CO., LTD

FOSHAN FEROSTEEL CO., LTD

FOSHAN FEROSTEEL CO., LTD
FOSHAN FEROSTEEL CO., LTD

FOSHAN FEROSTEEL CO., LTD

FOSHAN FEROSTEEL CO., LTD
FOSHAN FEROSTEEL CO., LTD

FOSHAN FEROSTEEL CO., LTD

FOSHAN FEROSTEEL CO., LTD
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What is the purpose and requirements of bright annealing of stainless steel
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What is the purpose and requirements of bright annealing of stainless steel

  • Categories:FAQS
  • Author:Ferosteel
  • Origin:Ferosteel
  • Time of issue:2020-05-19 10:45
  • Views:

(Summary description)Clear work hardening to obtain satisfactory metallographic structure     Bright annealing furnace is mainly used for heat treatment of stainless steel products under protective atmosphere. When the performance requirements are different, the requirements for the metallographic structure after bright annealing are different, and the process of bright heat treatment is also different.     The typical heat treatment process of 300 series austenitic stainless steel is solution treatment. During the temperature rise process, the carbide is dissolved into austenite, heated to 1050 ~ 1150 ℃, properly kept for a short time, so that the carbide is completely dissolved in the austenite, and then quickly cooled to below 350 ℃ to obtain a supersaturated solid solution that is uniform Unidirectional austenite structure. The key to this heat treatment process is rapid cooling, which requires a cooling rate of 55 ° C / s and quickly passes through the reprecipitation temperature range (550-850 ° C) after carbide solid solution. Keep the heat preservation time as short as possible, otherwise the grains will be coarse and affect the surface finish.     The heating temperature of 400 series ferritic stainless steel is relatively low (about 900 ℃), and slow cooling is often used to obtain annealed softening structure. Martensitic stainless steel is annealed, and it can also be quenched and tempered in sections.     It can be seen from the above that 300 series and 400 series stainless steels differ greatly in heat treatment system. To obtain a qualified metallographic structure, the cooling section of the bright annealing furnace requires a lot of room for adjustment. Therefore, modern advanced bright annealing furnaces often use strong convection cooling in their cooling section, with three cooling sections, which can adjust the air volume independently. It is divided into three sections along the width direction of the strip, and the cooling rate in the width direction of the strip is adjusted by the air flow diversion to control the plate shape.     Another key issue in the heat treatment of stainless steel cold-rolled strip is that the entire strip is required to be uniform in width and length. The muffle-type bright annealing furnace adopts a large-sized muffle tube, which uniformly organizes the heating airflow spirally from the outside of the muffle tube, so that the strip steel is heated evenly. In order to ensure the uniformity of the strip along the length, the linear velocity of the strip in the furnace must be kept constant. Therefore, before and after the modern vertical bright heat treatment furnace are equipped with roller tension adjustment device that can be precisely adjusted. It must not only make the speed of the steel strip import and export meet the requirements of the heat treatment speed, and is not affected by the empty or full sleeve of the looper. Claim.     Obtain an oxidation-free shiny surface     Bright annealing is the heat treatment of strip steel under H2 protective atmosphere. To meet the requirements of the BA board, the protective atmosphere in the furnace must be controlled very strictly to avoid oxidation as much as possible. How does oxidation occur under a protective atmosphere of H2     The main alloy components of stainless steel include Fe, Cr, Ni, Mn, Ti, Si and so on. In the annealing temperature range, the oxidation of Fe and Ni is not the main problem. But the oxidation range of Cr, Mn, Si, Ti is just in the heating temperature range. It is the oxidation of these alloy elements that affects the surface brightness of the strip. In particular, the oxidation of chromium will dechromize the surface of the strip steel, which will reduce the corrosion resistance of stainless steel. When Cr content is 17% ~ 18% and Ti content is 0.5%, H2 dew point must be lower than -60 ℃, in order to avoid the oxidation of Cr and Ti in the heating range of 800C ~ 1150 ℃.     At the same time, how to maintain the purity of the protective gas in the furnace also needs attention. In this regard, the muffle cover has good sealing performance, and no pollution of the protective atmosphere such as the material of the electric heating furnace body will occur, providing a purer environmental space. In addition, the strip steel inlet and outlet of the vertical furnace are located at the lowermost part of the furnace, and the furnace pressure is stable, so the risk of air entry is much smaller than that of the horizontal furnace. However, the import and export sealed boxes of the bright annealing furnace, the strip conveying section, the tension adjustment roller and the furnace top guide roller box should ensure that the sealing requirements of parts per million (ppM level) are met, so that oxygen and water vapor cannot enter and protect the gas Can't let out.

What is the purpose and requirements of bright annealing of stainless steel

(Summary description)Clear work hardening to obtain satisfactory metallographic structure

    Bright annealing furnace is mainly used for heat treatment of stainless steel products under protective atmosphere. When the performance requirements are different, the requirements for the metallographic structure after bright annealing are different, and the process of bright heat treatment is also different.

    The typical heat treatment process of 300 series austenitic stainless steel is solution treatment. During the temperature rise process, the carbide is dissolved into austenite, heated to 1050 ~ 1150 ℃, properly kept for a short time, so that the carbide is completely dissolved in the austenite, and then quickly cooled to below 350 ℃ to obtain a supersaturated solid solution that is uniform Unidirectional austenite structure. The key to this heat treatment process is rapid cooling, which requires a cooling rate of 55 ° C / s and quickly passes through the reprecipitation temperature range (550-850 ° C) after carbide solid solution. Keep the heat preservation time as short as possible, otherwise the grains will be coarse and affect the surface finish.

    The heating temperature of 400 series ferritic stainless steel is relatively low (about 900 ℃), and slow cooling is often used to obtain annealed softening structure. Martensitic stainless steel is annealed, and it can also be quenched and tempered in sections.

    It can be seen from the above that 300 series and 400 series stainless steels differ greatly in heat treatment system. To obtain a qualified metallographic structure, the cooling section of the bright annealing furnace requires a lot of room for adjustment. Therefore, modern advanced bright annealing furnaces often use strong convection cooling in their cooling section, with three cooling sections, which can adjust the air volume independently. It is divided into three sections along the width direction of the strip, and the cooling rate in the width direction of the strip is adjusted by the air flow diversion to control the plate shape.

    Another key issue in the heat treatment of stainless steel cold-rolled strip is that the entire strip is required to be uniform in width and length. The muffle-type bright annealing furnace adopts a large-sized muffle tube, which uniformly organizes the heating airflow spirally from the outside of the muffle tube, so that the strip steel is heated evenly. In order to ensure the uniformity of the strip along the length, the linear velocity of the strip in the furnace must be kept constant. Therefore, before and after the modern vertical bright heat treatment furnace are equipped with roller tension adjustment device that can be precisely adjusted. It must not only make the speed of the steel strip import and export meet the requirements of the heat treatment speed, and is not affected by the empty or full sleeve of the looper. Claim.

    Obtain an oxidation-free shiny surface

    Bright annealing is the heat treatment of strip steel under H2 protective atmosphere. To meet the requirements of the BA board, the protective atmosphere in the furnace must be controlled very strictly to avoid oxidation as much as possible. How does oxidation occur under a protective atmosphere of H2
    The main alloy components of stainless steel include Fe, Cr, Ni, Mn, Ti, Si and so on. In the annealing temperature range, the oxidation of Fe and Ni is not the main problem. But the oxidation range of Cr, Mn, Si, Ti is just in the heating temperature range. It is the oxidation of these alloy elements that affects the surface brightness of the strip. In particular, the oxidation of chromium will dechromize the surface of the strip steel, which will reduce the corrosion resistance of stainless steel. When Cr content is 17% ~ 18% and Ti content is 0.5%, H2 dew point must be lower than -60 ℃, in order to avoid the oxidation of Cr and Ti in the heating range of 800C ~ 1150 ℃.

    At the same time, how to maintain the purity of the protective gas in the furnace also needs attention. In this regard, the muffle cover has good sealing performance, and no pollution of the protective atmosphere such as the material of the electric heating furnace body will occur, providing a purer environmental space. In addition, the strip steel inlet and outlet of the vertical furnace are located at the lowermost part of the furnace, and the furnace pressure is stable, so the risk of air entry is much smaller than that of the horizontal furnace. However, the import and export sealed boxes of the bright annealing furnace, the strip conveying section, the tension adjustment roller and the furnace top guide roller box should ensure that the sealing requirements of parts per million (ppM level) are met, so that oxygen and water vapor cannot enter and protect the gas Can't let out.

  • Categories:FAQS
  • Author:Ferosteel
  • Origin:Ferosteel
  • Time of issue:2020-05-19 10:45
  • Views:
Information

Clear work hardening to obtain satisfactory metallographic structure

    Bright annealing furnace is mainly used for heat treatment of stainless steel products under protective atmosphere. When the performance requirements are different, the requirements for the metallographic structure after bright annealing are different, and the process of bright heat treatment is also different.

    The typical heat treatment process of 300 series austenitic stainless steel is solution treatment. During the temperature rise process, the carbide is dissolved into austenite, heated to 1050 ~ 1150 ℃, properly kept for a short time, so that the carbide is completely dissolved in the austenite, and then quickly cooled to below 350 ℃ to obtain a supersaturated solid solution that is uniform Unidirectional austenite structure. The key to this heat treatment process is rapid cooling, which requires a cooling rate of 55 ° C / s and quickly passes through the reprecipitation temperature range (550-850 ° C) after carbide solid solution. Keep the heat preservation time as short as possible, otherwise the grains will be coarse and affect the surface finish.

    The heating temperature of 400 series ferritic stainless steel is relatively low (about 900 ℃), and slow cooling is often used to obtain annealed softening structure. Martensitic stainless steel is annealed, and it can also be quenched and tempered in sections.

    It can be seen from the above that 300 series and 400 series stainless steels differ greatly in heat treatment system. To obtain a qualified metallographic structure, the cooling section of the bright annealing furnace requires a lot of room for adjustment. Therefore, modern advanced bright annealing furnaces often use strong convection cooling in their cooling section, with three cooling sections, which can adjust the air volume independently. It is divided into three sections along the width direction of the strip, and the cooling rate in the width direction of the strip is adjusted by the air flow diversion to control the plate shape.

    Another key issue in the heat treatment of stainless steel cold-rolled strip is that the entire strip is required to be uniform in width and length. The muffle-type bright annealing furnace adopts a large-sized muffle tube, which uniformly organizes the heating airflow spirally from the outside of the muffle tube, so that the strip steel is heated evenly. In order to ensure the uniformity of the strip along the length, the linear velocity of the strip in the furnace must be kept constant. Therefore, before and after the modern vertical bright heat treatment furnace are equipped with roller tension adjustment device that can be precisely adjusted. It must not only make the speed of the steel strip import and export meet the requirements of the heat treatment speed, and is not affected by the empty or full sleeve of the looper. Claim.

    Obtain an oxidation-free shiny surface

    Bright annealing is the heat treatment of strip steel under H2 protective atmosphere. To meet the requirements of the BA board, the protective atmosphere in the furnace must be controlled very strictly to avoid oxidation as much as possible. How does oxidation occur under a protective atmosphere of H2
    The main alloy components of stainless steel include Fe, Cr, Ni, Mn, Ti, Si and so on. In the annealing temperature range, the oxidation of Fe and Ni is not the main problem. But the oxidation range of Cr, Mn, Si, Ti is just in the heating temperature range. It is the oxidation of these alloy elements that affects the surface brightness of the strip. In particular, the oxidation of chromium will dechromize the surface of the strip steel, which will reduce the corrosion resistance of stainless steel. When Cr content is 17% ~ 18% and Ti content is 0.5%, H2 dew point must be lower than -60 ℃, in order to avoid the oxidation of Cr and Ti in the heating range of 800C ~ 1150 ℃.

    At the same time, how to maintain the purity of the protective gas in the furnace also needs attention. In this regard, the muffle cover has good sealing performance, and no pollution of the protective atmosphere such as the material of the electric heating furnace body will occur, providing a purer environmental space. In addition, the strip steel inlet and outlet of the vertical furnace are located at the lowermost part of the furnace, and the furnace pressure is stable, so the risk of air entry is much smaller than that of the horizontal furnace. However, the import and export sealed boxes of the bright annealing furnace, the strip conveying section, the tension adjustment roller and the furnace top guide roller box should ensure that the sealing requirements of parts per million (ppM level) are met, so that oxygen and water vapor cannot enter and protect the gas Can't let out.

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