Cooling process for manufacturing cracking connecting rod blank from 38MnVS6 medium-carbon non-quenched and tempered steel

Abstract

The invention discloses a cooling process for manufacturing a cracking connecting rod blank from 38MnVS6 medium-carbon non-quenched and tempered steel. The cooling process comprises the following steps that before the connecting rod blank is cooled, quickly cooling in a box-type furnace, slowly cooling in the box-type furnace, slowly cooling in air outside the furnace and stacking and cooling in aheat preservation material frame are conducted in sequence at the temperature of not less than 830 DEG C; quick cooling in the box-type furnace is conducted from more than or equal to 830 DEG C to 710+ / -20 DEG C, and the cooling speed is 1.5-2.5 DEG C / S; slowly cooling in the box-type furnace is conducted from 710+ / -20 DEG C to 580+ / -20 DEG C, wherein the cooling speed is 0.4-1.3 DEG C / S; slowlycooling the air outside the furnace is conducted from 580+ / -20 DEG C to 480+ / -20 DEG C, wherein the cooling speed is 0.13-0.20 DEG C / S; and stacking and cooling in the heat preservation material frameare conducted from 480+ / -20 DEG C to room temperature. After cooling of the four cooling links, the mechanical property of the forged connecting rod blank is qualified, the metallographic structure is pearlite and network ferrite which are evenly distributed, the grain size of the edge of the blank is 4-6 levels, the grain size of the core of the blank is 2.5-4 levels, the machining performance and cracking performance of the blank are good, and the cracking surface has no brittle fracture of obvious plastic deformation.

Description

technical field [0001] The invention belongs to the field of automobile materials and technology, and in particular relates to a cooling process for making a blank of an expansive connecting rod made of 38MnVS6 medium carbon non-quenched and tempered steel. Background technique [0002] For a long time, alloy structural steel has been used to forge the blanks of the engine connecting rod body and connecting rod cover respectively, and then undergo quenching and tempering heat treatment, machine the connecting rod body and connecting rod cover separately, and assemble them into a connecting rod assembly. However, if the engine connecting rod blank is forged with non-quenched and tempered steel, the connecting rod body and the connecting rod cover can be integrally forged, and the connecting rod head can be broken into the connecting rod body and the connecting rod cover by using the expanding and breaking process. The forging process generally consists of the following proces...

AI Technical Summary

Problems solved by technology

[0004] Aiming at the problems existing in the prior art that the metallographic structure of the 38MnVS6 fractured connecting rod is difficult to control and the quality of the fractured section is poor due to different cooling processes, the present invention provides a 38MnVS6 medium carbon non-quenched and tempered steel to make the fractured connecting rod For the cooling process of the blank, by setting the cooling process parameters after forging, the cooling rate of the blank after forging is controlled in stages. After cooling in four cooling stages, the mechanical properties and metallographic structure of the connecting rod blank meet the product technical requirements, and the blank rises. Good fracture performance, brittle fracture without obvious plastic deformation

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