Nb-containing Cr-Ni carburizing steel for cold forming and cold forming method of part
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A technology of cold forming and carburizing steel, which is applied in the field of cold forming of Cr-Ni carburizing steel and parts containing Nb for cold forming, which can solve the problems of cold extrusion forming resistance, carburizing treatment grain growth, etc. question
Active Publication Date: 2021-09-10
DONGFENG COMML VEHICLE CO LTD
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[0003] Chinese invention patent (patent number CN201810775502.X) discloses the application of a Nb, Ti composite microalloyed high-temperature pinhole carburized heavy-duty gear steel, Nb, Ti composite microalloyed into special carburized steel ...
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Embodiment 1
[0037] The inner ring gear of a heavy-duty gearbox sub-box is produced by carburizing, and the depth of carburizing process requires 0.8-1.1mm.
[0038] Cr-Ni carburizing steel for cold forming containing Nb: chemical composition mass percentage includes: C 0.14%, Mn 0.75%, P0.016%, S 0.025%, Cr 1.00%, Al 0.020%, Nb 0.06%, O 10ppm, N 120ppm, Si 0.20%, Ni 1.20%, Cu 0.12%, Mo 0.05%, V 0.03%, and the rest are Fe and unavoidable impurities.
[0039]Forming process of the present invention: Nb-containing cold forming with Cr-Ni carburizing steel blanking induction heating 1100°C, after the ring is formed, the temperature is not lower than 860°C, sent to a 950°C isothermal normalizing furnace, kept for 1 hour, cooled to 650°C for heat preservation 2.5h, shot peening to remove scale. Parts are heated to 760°C, held for 4 hours, cooled to 700°C for 4 hours; heated to 760°C, held for 4 hours, cooled to 700°C for 4 hours; heated to 760°C, held for 4 hours, cooled to 700°C for 4 hours, ...
Embodiment 2
[0044] The inner ring gear of a heavy-duty gearbox sub-box is produced by carburizing, and the depth of carburizing process requires 0.8-1.1mm.
[0045] Cr-Ni carburizing steel for cold forming containing Nb: chemical composition mass percentage includes: C 0.10%, Mn 1.10%, P0.016%, S 0.025%, Cr 1.20%, Al 0.020%, Nb 0.050%, O 10ppm, N 120ppm, Si 0.10%, Ni 1.40%, Cu 0.18%, Mo 0.05%, V 0.03%, and the rest are Fe and unavoidable impurities.
[0046] Forming process of the present invention: Nb-containing cold forming with Cr-Ni carburizing steel blanking induction heating 1250°C, the temperature after rolling ring forming is not lower than 860°C, sending it into an isothermal normalizing furnace at 1000°C, holding for 2 hours, cooling to 700°C for heat preservation 2h, shot peening to remove scale. Parts are heated to 780°C, held for 2 hours, cooled to 680°C for 2 hours; heated to 780°C, held for 2 hours, cooled to 680°C for 2 hours; heated to 780°C, held for 2 hours, cooled to ...
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Abstract
The invention discloses a Nb-containing Cr-Ni carburizing steel for cold forming and a cold forming method of a part. The content of C is reduced and the content of spherical pearlite obtained after spheroidizing annealing is reduced, so that the hardness of a blank is effectively controlled; high-content Ni is added, so that plasticity and toughness of ferrite in the blank are improved, and deformation micro-cracks are not prone to occurring in the interior and on the surface of the part during cold forming; by means of the solid solution characteristic of Nb, N and C in steel, part of Nb, N and C are separated out at an austenitizing temperature of 1100-1250 DEG C, and steel grains can be prevented from being coarsened at a forging temperature; and nbN/NbC is completely separated out, so that the grain size is guaranteed to be smaller than 7 grades, and intermediate cooling treatment is not needed. Pre-oxidation adopts sectional control, the surface of a workpiece is activated, the inside and outside temperature difference is reduced, the inside and outside heating is more uniform, and the internal structure of the part starts repeated crystallization, so that the internal and external structures are more uniform, and thermal treatment deformation aggravation caused by rapid temperature rise is avoided; and residual austenite on the surface of a Ni-containing steel quenching part is reduced, so that the surface hardness is improved to be not smaller than HRC61.
Description
technical field [0001] The invention belongs to the technical field of metallurgy and cold forming of parts, and in particular relates to a Cr-Ni carburizing steel for cold forming containing Nb and a cold forming method of parts. Background technique [0002] Cylindrical gears and ring parts of heavy-duty gearboxes are formed by cold extrusion, and the local deformation is large during molding, resulting in uneven cross-sectional deformation, and the grains are easy to coarsen during subsequent carburizing heat treatment. At present, domestic cold extrusion forming parts widely adopt carburizing steel specified in GB / T5216. The blank is subjected to spheroidizing annealing or complete annealing process, and the hardness range is HB135~145. When cold extrusion forming, the resistance is large, it is not easy to form, and it is partially deformed. Large areas are prone to internal micro-cracks. In addition, for cold forming parts adopting continuous furnace carburizing or co...
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