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Application of Low Carbon Martensite Technology in High Strength Bolts
Time：
2024-12-18
Application of Low Carbon Martensite Technology in High Strength Bolts
First, low-carbon martensite technology has the following characteristics:
(1) The quenching heating temperature is above Ac3 (80-120 ℃). Considering the effect of quenching strengthening, appropriately increasing the quenching heating temperature is beneficial to the homogenization of austenite, refining grains, improving the hardenability of steel and shortening the heating time. In addition, the low-carbon martensite hardening effect depends not only on the quenching heating temperature, but also on the temperature at which the fastener is quenched.
⑵ Intense quenching cooling method of chilling and deep cooling shall be adopted. Low-carbon martensite can be obtained after intensive quenching (5%-10% NaCl solution quenching or PAG aqueous solution) of low-carbon steel or low-carbon alloy steel. Low carbon, low alloy structural steel with strong quenching will not produce quenching crack. The low carbon medium and high alloy steel due to the high carbon equivalent (>0.45%) quenching cooling should adopt appropriate cooling methods and cooling medium. Such as: water-air, water-oil or oil-cold.
(3) The low carbon martensite can be directly used without tempering after quenching.
The larger the size of the fastener section, the higher the hardness after quenching. The hardness of different sizes of steel after quenching is shown in Table 1.
