CN111004894A

CN111004894A - Processing technology for uniform and stable quenching hardness of No. 45 high-quality carbon structural steel

Info

Publication number: CN111004894A
Application number: CN201911376651.XA
Authority: CN
Inventors: 傅世闯; 陈庚
Original assignee: Dalian Demaishi Precision Technology Co ltd
Current assignee: Dalian Demaishi Precision Technology Co ltd
Priority date: 2019-12-27
Filing date: 2019-12-27
Publication date: 2020-04-14

Abstract

A45 # high-quality carbon structural steel quenching hardness uniform and stable processing technology comprises the steps of (1) smelting raw materials; step (2) rolling, drawing and cutting off; step (3) NC processing; step (4), quenching in a mesh belt furnace; and (5) grinding the excircle. The invention adds Cr with proper content, which can not increase the cost of raw materials, and the chemical component content of the raw materials still meets the standard requirement, and the heat treatment process uses over-speed quenching oil to replace rapid bright quenching oil. Thoroughly solves the problem of uneven hardness and soft spots of the No. 45 steel during heat treatment quenching; the material cost is kept unchanged, the heat treatment qualification rate of the product reaches 100 percent, the production cost is greatly reduced, and the product quality is ensured.

Description

Processing technology for uniform and stable quenching hardness of No. 45 high-quality carbon structural steel

Technical Field

The invention relates to a uniform and stable quenching hardness processing technology of No. 45 high-quality carbon structural steel, in particular to a processing technology of small-sized shaft parts.

Background

The No. 45 steel is a high-quality carbon structural steel, the hardness of raw materials is not high, the cutting processing is easy, the cost of the raw materials is lower than that of alloy steel, and the raw materials have higher mechanical properties after heat treatment, so the steel is widely applied to automobiles and motorcycles, particularly connecting rods, bolts, gears, shafts and the like under the alternating load work, huge friction force needs to be borne in the work, and the self hardness, the wear resistance, the service life and the like are improved by adopting a quenching mode. However, the 45 steel is a medium carbon steel, the quenching effect is not good, and the 45 steel always generates 'quenching soft spots' in the actual production process, so that the products after heat treatment need to be sorted by hundreds of hardness, and even the scrapping condition of the products in batch due to the hardness problem often occurs. Taking an engine cooling fan motor shaft of phi 8 x 45.9 as an example, the hardness requirement of heat treatment is HRC54 +/-2, and the traditional processing technology is as follows: the defects of the raw materials and the processing process are that the hardness of the product after heat treatment is not uniform, the soft points of the product are more, and hundred percent hardness selection and even scrapping treatment have to be carried out, because the traditional No. 45 steel has low alloy element content (shown in table 1), poor whole hardenability and poor cooling effect of common rapid bright quenching oil, the quenching hardness of the product is not uniform.

Disclosure of Invention

The invention aims to provide a processing technology for the No. 45 high-quality carbon structural steel, which can solve the problems of uneven quenching hardness and soft spots of the No. 45 steel product, reduce the rejection rate of the product and ensure the stable quality of the product and has even and stable quenching hardness.

The processing technology for the No. 45 high-quality carbon structural steel with uniform and stable quenching hardness comprises the following steps:

smelting raw materials: 0.15 to 0.25 percent of Cr element is added during the smelting of No. 45 raw material;

step (2) rolling, drawing and cutting: cutting off the material by a cutting machine after the disc material is drawn;

step (3), NC processing: turning by using a chicken numerical control machine, and then rolling patterns by using a thread rolling machine;

step (4) mesh belt furnace quenching: in the mesh belt furnace quenching process, the quenching process adopts high-temperature quenching, the heating and heat preservation time is 45-60 minutes, the temperature of the mesh belt furnace is set to be 840 ℃ in a first zone, 860 ℃ in a second zone, 860 ℃ in a third zone and 860 ℃ in a fourth zone, and overspeed quenching oil is used for replacing common quick bright quenching oil in the quenching and cooling process;

cylindrical grinding in step (5): and (4) grinding the outer diameter by using a centerless grinder.

Compared with the prior art, the invention has the following advantages:

(1) the proper content of Cr element is added, the cost of raw materials is not increased, the chemical component content of the raw materials still meets the standard requirement, and the rapid bright quenching oil is replaced by the overspeed quenching oil in the heat treatment process.

(2) Thoroughly solves the problem of uneven hardness and soft spots of the No. 45 steel during heat treatment quenching; the material cost is kept unchanged, the heat treatment qualification rate of the product reaches 100 percent, the production cost is greatly reduced, and the product quality is ensured.

Detailed Description

Example 1

smelting raw materials: 0.22 percent of Cr element is added during smelting of No. 45 raw material;

A processing technology for the No. 45 high-quality carbon structural steel with uniform and stable quenching hardness takes the processing of a No. 45 steel engine cooling fan motor shaft with phi 8 x 45.9 as an example,

the chemical components of the raw materials of the motor shaft of the original conventional 45# steel engine cooling fan are shown in the table 1, and the hardness values after heat treatment are shown in the table 2:

TABLE 1 phi 8.0 engine cooling fan motor shaft stock composition

Element(s)	C	Mn	Si	P	S	Cr	Ni	Cu
									Standard ingredients	0.42	0.5	0.17	≤	≤	≤	≤	≤
	0.50	0.8	0.37	0.035	0.035	0.25	0.30	0.25
									Actual measurement result	0.46	0.58	0.22	0.013	0.005	0.082	0.011	0.013

TABLE 2 hardness values after heat treatment (requirement: HRC 54. + -. 2)

As shown in the table, the hardness values of all parts of the product processed by the conventional 45# steel raw material are very uneven after the product is subjected to heat treatment by using common quick bright quenching oil, the number of soft points on the product is large, the qualification rate is extremely low, and the product requirements of customers cannot be met.

After processing using this example, 45# raw material chemistry and post heat treatment hardness values are shown in tables 3 and 4:

TABLE 3 raw material composition of motor shaft of cooling fan for engine phi 8.0

TABLE 4 hardness values after heat treatment (requirement: HRC 54. + -. 2)

According to the hardness test results, the hardness value of the product after heat treatment has no soft point by using the processing mode of the method, and the measured hardness value meets the technical requirements.

Claims

1. A processing technology for uniformly and stably quenching hardness of No. 45 high-quality carbon structural steel is characterized by comprising the following steps of: