Low-deformation gear steel and manufacturing method thereof

Abstract

The invention relates to low-deformation gear steel. The gear steel comprises the following chemical components in percentage by weight: 0.10 to 0.30 percent of C, 0.15 to 0.25 percent of Si, 0.60 to 0.90 percent of Mn, less than or equal to 0.030 percent of P, 0.010 to 0.035 percent of S, 0.85 to 1.25 percent of Cr, 0.15 to 0.35 percent of Mo, 0.020 to 0.050 percent of Al, less than or equal to 0.20 percent of Cu, 0.0100 to 0.0250 percent of N, and the balance of Fe and inevitable impurities. A manufacturing method for the steel comprises the following steps of: performing primary smelting in an electric furnace, refining steel ladles, degassing in vacuum, and bulling the ladles at the temperature of between 1550 and 1570 DEG C; performing continuous casting with superheat degree of 20 to 40 DEG C at the speed of 0.6 to 2.10m / min, and performing slow cooling or hot charging on the continuously cast bloom in a slow cooling pit; cooling the steel billet to the temperature of less than 700 DEG C at a preheating section, preserving the heat at a heating section I of 880 to 980 DEG C, then preserving the heat at a heating section II of 950 and 1200 DEG C, preserving the heat at a soaking section of 1180 and 1220 DEG C, and performing external rolling, wherein the total heating time is 195 to 210 minutes, and the temperature difference between the two sides of the square billet is less than or equal to 30 DEG C; and discharging the steel billet out of the furnace, wherein the rolling start temperature is 1155 to 1200 DEG C, and the final rolling temperature is more than 950 DEG C.

Description

technical field [0001] The invention relates to an alloy steel, in particular to a low-deformation gear steel mainly used in the manufacture of gearboxes and drive axle gears of transportation tools such as vehicles and engineering machinery, and a manufacturing method thereof. Background technique [0002] With the development of the times and the advancement of science and technology, people have higher and higher requirements for the comfort of cars, and the vibration and noise generated during the running of cars have received more and more attention. The noise of speed change and transmission system is one of the main noise sources of automobiles. The main reason is that the gears run unevenly due to the low precision of the gears. In order to improve the gear precision, in addition to improving the machining and heat treatment process of gears, higher requirements should be put forward for the structure and performance of gear steel, the raw material for gears. [000...

AI Technical Summary

Problems solved by technology

[0004] CN1311339A discloses a quenching method for reducing workpiece deformation, which is characterized in that the rotation angle parameter of the material tray is increased during quenching, the workpiece can be placed in a manner that reduces high-temperature deformation in the carburizing stage, and the material can be turned over by a turning mechanism after carburizing. The disc is flipped forward and sideways 0-90 degrees, thus allowing the workpiece to enter the quenching medium at an optimal angle, thus improving deformation, but not involving the content of the raw material

This method does not consider the effects of chemical composition and thermal processing on grain size and banded structure

[0008] CN101381803A discloses a method for controlling the strip structure of gear steel. Under the premise of not changing the existing technological process, different rolling temperatures of 1000-1100°C and finishing rolling temperatures of 750-880°C are controlled respectively, so that the steel ferrite +Pearlite band structure grade ≤2.5 grade, the rolling temperature involved is low, which is not conducive to the refinement of grain size

[0010] Most of the above inventions do not consider the influence of grain size and band structure on heat treatment deformation of gear steel

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