Manufacture technology for improving toughness of non-quenched and tempered steel forging

Abstract

The invenmtion relates to a manufacture technology of a forging, in particular to a manufacture technology for improving the toughness of a non-quenched and tempered steel forging, which comprises the following working procedures of: blanking-induction heating-dummying-finish forging-trimming-controlled cooling-cooling in heap in a charging box-shot blasting-magnetically inspecting-machining; the working procedure of controlled cooling comprises the following steps of: trimming workpieces, immediately arranging the workpieces on a transmission band which moves at a certain speed in a dispersing way, and under the cooling condition of compulsory aerating or water mist spraying, cooling the workpieces to some temperature within 520 DEG C-650 DEG C at the cooling speed of 2.0 DEG C/s-50.0 DEG C/s, and then cooling the workpieces in heap in the charging box; and the working procedure of cooling in heap in the charging box comprises the following step of slowly cooling the workpieces to room temperature at the cooling speed which is less than 5 DEG C/min. According to the manufacture technology, the precipitation of an eutectoid ferrite at an original austenitic crystal boundary in the form of net and the appearance of the bainite tissue can be eliminated or avoided, more intra-granular ferrite can be obtained, and the toughness and the plasticity of parts can be improved.

Description

technical field [0001] The invention relates to a manufacturing process of a forging, in particular to a manufacturing process for improving the toughness of a non-quenched and tempered steel forging. Background technique [0002] Micro-alloyed non-quenched and tempered steels, medium-carbon vanadium-containing micro-alloyed steels have been studied earlier and widely used, because such steels can precipitate a large amount of finely dispersed alloy carbon and nitrogen compounds in the process of rolling and forging cooling, and precipitate strengthening , and obtain the comprehensive mechanical properties equivalent to quenched and tempered steel after quenched and tempered treatment, eliminating the need for quenching and tempering treatment process, saving energy and cost, and has been widely used in petroleum, automobile, machinery and other industries. This kind of non-quenched and tempered steel obtains ferrite + pearlite structure after forging and controlled cooling....

AI Technical Summary

Problems solved by technology

The disadvantage of the cooling method of this patent is: in the process of rapid cooling to about 600°C in the natural air cooling zone, because there is no clear requirement on the cooling rate, when the cooling rate is not enough, pro-eutectoid iron will appear in the CCT curve of the steel Network proeutectoid ferrite is precipitated along the original austenite grain boundary within the precipitation range of the matrix, thus making the toughness of the material worse

The disadvantages of the cooling method of this patent are: the time from entering the furnace to being out of the furnace by controlled cooling after forging is short (less than 13 minutes), and during this process and the subsequent cooling process are continuous cooling (greater than 9°C / min) , for some non-quenched and tempered steels with better stability of supercooled austenite, bainite structure will appear, thus making the toughness of the material worse

The disadvantage of the cooling method of this patent is that when the forging is cooled in a furnace at 884°C to 552°C, the cooling rate is relatively slow (less than 1.4°C / s), and it is easy to pro-eutectoid ferrite in the CCT curve of the steel In the precipitation range, network proeutectoid ferrite is precipitated along the prior austenite grain boundary, thus making the toughness of the material worse

In addition, the controlled cooling method takes a short time from entering the furnace to being discharged after forging (less than 13 min), and during this process and the subsequent cooling process is continuous cooling (greater than 9°C / min). Some non-quenched and tempered steels with better stability of supercooled austenite will appear bainite structure, which will also make the toughness of the material worse

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