Mild steel quench annealing can reduce hardness

Do you know the quenching process of low carbon steel? If you are using hypoeutectoid steel, the quenching temperature needs to be heated to between 30 and 50 degrees Celsius. After heating, it should be kept for a period of time before cooling. Interested If you want to learn about it with Kehua editor! Heat treatment process steel commonly used heat treatment processes are as follows: 1. Quenching For hypoeutectoid steel, that is, low carbon steel and medium carbon steel heated to 30-50 ℃ above Ac3, Keep it at this temperature for a period of time to make the structure of the steel all become austenite, and then rapidly cool (water cooling or oil cooling), so that the austenite has no time to decompose and form a martensitic structure, which is called quenching. Carbon steel in welding When it is used with some alloy steels, the quenching phenomenon may occur in the near seam area and become hard, and it is easy to form cold cracks, which should be avoided during the welding process. Tempering Tempering is a heat treatment method in which the quenched workpiece is reheated to a temperature below A1, and then cooled in air or water after being kept for a period of time. The purpose of tempering is to reduce the hardness of quenched steel, improve plasticity and toughness, reduce internal stress, and adjust microstructure in order to obtain good comprehensive mechanical properties. According to the tempering temperature, it can be divided into low temperature tempering (150-250 °C), medium temperature tempering (350-450 °C), high temperature tempering (500-650 °C) High temperature tempering is carried out immediately after quenching. This operation of quenching and high temperature tempering is called quenching and tempering treatment. Normalizing Heating the steel to 30-50℃ above Ac3 or Accm, and cooling it in the air after heat preservation is called normalizing. After normalizing, many carbon steels and alloy steels have good mechanical properties and can refine the grains. For the welded structure, the quality of the weld can be improved after normalizing, which can eliminate the coarse grains, hardened structure and uneven structure in the weld area. Slow and uniform cooling is called annealing. Annealing reduces hardness, makes the material easier to machine, refines the grain of the steel, and relieves stress. Heating the steel to below Ac1 (usually 600-650 ℃), holding it for a certain period of time, and then cooling it in the air or furnace is stress relief annealing, also known as low temperature annealing. Stress relief annealing is mainly used to remove the welding residual stress of the welded structure. Low carbon steel quenching The above is the relevant introduction about low carbon steel quenching. Generally, after normalizing the alloy steel, it can improve the quality of the weld. If you want to know more information, please pay more attention to the Kehua website!