Decarburization and recarburization determination method for bolt under quenched state

Abstract

The invention relates to a decarburization and recarburization determination method for a bolt under a quenched state. The decarburization and recarburization determination method comprises the following steps: (1) cutting out a cross section sample from a part, corresponding to a thread, on the bolt under the quenched state; grinding the cut off sample; selecting three points on the sample, wherein the first point is a root of thread, the second point is a point shifting perpendicular to the axial direction of the bolt for 0.15 to 0.25mm from a top of thread to the root of thread, and the third point is a point intersected with the pitch line of the thread after transversely shifting for 0.10 to 0.20mm from the side of a thread tooth to the inner side; if the difference obtained by subtracting the hardness value of the second point from the hardness value of the first point is greater than or equal to 50HV, showing that the bolt is in decarburization; if the difference obtained by subtracting the hardness value of the first point from the hardness value of the third point is greater than or equal to 50HV, showing that the bolt is in recarburization. The decarburization and recarburization determination method disclosed by the invention is capable of performing decarburization and recarburization determination on the quenched bolt, therefore the phenomenon that batch products are unqualified is avoided; moreover, the generation time is shortened, and the production cost is reduced.

Description

technical field

[0001] The invention relates to a decarburization and carburization measuring method, in particular to a decarburization and carburization measuring method in a bolt quenched state. Background technique

[0002] Bolts are generally produced by cold heading. In order to implement cold heading production, the raw materials must first be peeled - spheroidizing annealing - acidic - phosphating - drawing (diameter fixed) - spheroidizing annealing - acidic - phosphating - fine drawing (Sizing) these several processes, then cold heading, quenching and tempering heat treatment after cold heading, among them, decarburization will occur during spheroidizing annealing and quenching, so recombination will be carried out during heat treatment Carbon treatment, however, whether there is decarburization or carburization in the product after recarburization treatment can only be detected by metallographic method or microhardness method after the product is tempered. [0003...

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