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Reduced temperature steel has superb strength and strength in reduced temperature environment, great welding performance, machining efficiency and deterioration resistance, are generally defined in the minimum temperature of a specific value of influence toughness in the requirement. In low temperature steels, aspects such as carbon, silicon, phosphorus, sulfur as well as nitrogen degrade the toughness at low temperature, among which phosphorus is thought about to be the most dangerous as well as must be dephosphorized at low temperature level in very early smelting. Mn, nickel as well as various other components can enhance the durability at low temperature level. With the boost of nickel web content by 1%, the critical change temperature of brittleness can be lowered by about 20 ℃. Reduced temperature level sturdiness, i.e. the capacity to prevent brittle failure from occurring as well as spreading out at low temperatures, is the most important element. Today we present the influence of alloying components on the reduced temperature durability of steel:
With the rise of carbon web content, the weak change temperature of steel enhances rapidly and also the weldability reduces, so the carbon content of low-temperature steel is restricted to much less than 0.2%.
The manganese exist in steel with the type of solid solution as well as can clearly improve the strength of steel at reduced temperature. In addition, manganese is an element that enlarges the Austenite area and also minimizes the improvement temperature level (A1 and A3). It is simple to obtain great and pliable ferrite and also pearlite grains, which can make the most of the effect power as well as reduce the brittle change temperature. Because of this, the Mn/C proportion ought to go to the very least equivalent to 3, which can not only reduce the fragile transition temperature level of steel, however also compensate for the reduction in mechanical properties triggered by the decline in carbon web content because of the boost of Mn.
Nickel can reduce the brittleness propensity as well as significantly lower the fragile shift temperature level. The effect of nickel on improving the low temperature level sturdiness of steel is 5 times that of manganese. The brittle shift temperature lowers by 10 ℃ with the boost of nickel content by 1%. This is due to the fact that the nickel does not respond with carbon, but all dissolved right into the solid service as well as the strengthening, nickel likewise makes the steel eutectoid indicate the reduced left, and also minimize the eutectoid point of carbon content and phase adjustment temperature (A1 and A2), so compared to various other carbon steel has the exact same carbon material, the variety of ferrite reduction as well as improvement, while the pearlite rise.
P 、 S 、 Pt 、 Pb 、 Sb.
These aspects are detrimental to the reduced temperature level sturdiness of steel. They produce segregation in steel, which reduces the surface area power of grain boundary, lowers the resistance of grain limit, as well as triggers the brittle fracture to stem from grain limit and also propagate along grain boundary till the crack is full.
Phosphorus can improve the toughness of steel however enhance the brittleness of steel, specifically the brittleness at low temperature. The fragile transition temperature is certainly raised, so the web content of phosphorus ought to be strictly limited.
H, O, N.
These aspects will certainly enhance the weak change temperature level of steel. Low temperature toughness can be enhanced by deoxidizing killed steels with silicon and light weight aluminum. However
WldSteel of steel, so aluminum killed steel has a lower fragile transition temperature than silicon eliminated steel.