Water toughening treatment of alloy steel castings and its development prospect

- Jan 24, 2019-

Alloy steel castings usually refer to carbon steel and low alloy steel castings, which have high strength, high toughness and good weldability.If heat resistance, pressure resistance, corrosion resistance, low temperature resistance and wear resistance are required, special high alloy steel castings are available.With the development of machinery manufacturing, steel castings are widely used.In the next ten years, cast steel has a broad market prospect at home and abroad.

 

Water toughening of alloy steel castings

 

The temperature of alloy steel casting must be above 950 before it enters water to avoid carbide precipitation.For this reason, the time from the casting to A water should not exceed 30s, and the water temperature should be kept below 30 degrees.The highest water temperature after quenching shall not exceed 60 degrees.When the water temperature is high, the mechanical properties of high manganese steel decrease obviously.The amount of water must be more than 8 times the weight of the casting and the lifting bar during the toughening treatment. If non-circulating water is used, the amount of water should be increased regularly.Use clean circulating water or use compressed air to agitate pool water.

The cooling of the casting can be accelerated by swinging the hanging basket when the casting is quenched by the hanging basket.The properties of castings directly affect the quality of machining, of which the hardness value is an important index to determine the machining of castings.Brinell hardness: mainly used for determination of casting, forging, non-ferrous metal parts, the hardness of hot rolled billet and annealing, measurement range ≯ HB450.Rockwell hardness :HRA is mainly used for high hardness test pieces. The hardness of materials and surface hardness higher than HRC67, such as cemented carbide, nitride steel, etc., can be measured within HRA>70.

 

 

In order to refine grain, homogenize structure and eliminate internal stress, steel casting must be normalized or annealed.The normalized steel has higher mechanical properties and lower cost than the annealed steel, so it is widely used.However, as the normalizing treatment will cause greater internal stress than annealing, it is only suitable for steel castings with carbon content less than 0.35%.Because of the good ductility of low carbon cast steel, it is not easy to crack when cooling.In order to reduce internal stress, high temperature tempering should be carried out after normalizing steel castings.For steel castings with carbon content 0.35%, complicated structure and easy to crack, they can only be annealed.Steel castings should not be quenched, or they will crack easily.www.wuxiorient.com