CN107350303B

CN107350303B - Production method of automobile shaft part steel

Info

Publication number: CN107350303B
Application number: CN201710426163.XA
Authority: CN
Inventors: 顾铁; 邵淑艳; 李英; 颉军定; 章照; 周阳; 高峰
Original assignee: Jiangyin Xingcheng Special Steel Works Co Ltd
Current assignee: Jiangyin Xingcheng Special Steel Works Co Ltd
Priority date: 2017-06-08
Filing date: 2017-06-08
Publication date: 2020-02-07
Anticipated expiration: 2037-06-08
Also published as: CN107350303A

Abstract

The invention relates to a production method of automobile shaft part steel, which takes a large-section continuous casting rectangular blank as a raw material, adopts a two-fire material forming process, ensures the compression ratio of cogging rolling and finished product rolling, and particularly adopts a large compression ratio when the finished product is rolled, wherein the compression ratio is more than or equal to 30 so as to control the depth of a decarburizing layer and the depth of surface defects of a hot rolled material. The technological process includes smelting → continuous casting → cogging and rolling + scarfing → flaw detection and grinding of intermediate blank → rolling of intermediate blank and flaw detection of finished product. The application produces a hot rolled material with shallow decarburized layer, high surface quality and high size precision to replace silvery processing, and is convenient for direct blanking and forming processing of customers.

Description

Production method of automobile shaft part steel

Technical Field

The invention relates to a production method of steel for automobile parts, in particular to a production method for replacing a bright silver bar with a hot rolled bar.

Background

In order to save energy, improve the material utilization rate and reduce the production cost, the automobile shaft part needs to adopt smaller processing amount or even zero processing amount when the material section is processed by a forming machine, namely, part of the surface of the material section can not be processed during the forming processing. The surface defect depth of the material section is usually required to be less than or equal to 0.1mm, and the out-of-roundness is required to be less than or equal to 0.15 mm. The above requirements are difficult to be met by a general hot rolled material due to the limitation of production conditions. Generally, in order to meet the requirements, the raw material bar needs to be processed with silver bright and then processed with a forming machine. The silver processing is to straighten, turn and finish the hot rolled bar to remove or reduce the surface defects of decarburization, cracks, warping and the like of the material and improve the dimensional precision of the material so as to meet the processing requirements of parts. However, this will inevitably reduce the material utilization rate, reduce the production efficiency and increase the production cost. The smaller the specification is, the higher the material loss rate at the time of silver processing tends to be. For the material with the specification range less than or equal to phi 60mm, the silver bright is replaced by hot rolling, the silver bright processing process is omitted, and the cost advantage is obvious.

In conclusion, in order to meet the modern production requirements of low consumption, environmental protection, high efficiency and economy, the hot rolled bar with high surface quality, high dimensional precision and good internal quality can be produced, and the hot rolled bar is directly fed into a material section and then is processed by a forming machine so as to save the step of additionally processing the bar before processing.

Disclosure of Invention

The invention aims to provide a production method of a hot-rolled bar with high surface quality and high dimensional accuracy. The method is suitable for producing the bar with the specification range less than or equal to phi 60mm so as to save the procedure of producing the bright and silvery bar by customers.

The technical scheme adopted by the invention for solving the problems is as follows: a method for producing steel for axle parts of car features that the continuous casting rectangular blank with large cross-section is used as raw material, and two-heating process including cogging rolling and intermediate blank rolling is used to ensure the compression ratio of cogging rolling and finished product rolling, and a large compression ratio (greater than or equal to 30) is used to control the depth of decarburized layer and surface defect of hot rolled product.

Specifically, the process flow, smelting → continuous casting → cogging and rolling + scarfing → defect detection and grinding of intermediate billet → rolling of intermediate billet → defect detection of finished product, specifically comprises the following operations

1) Smelting

Designing corresponding chemical components according to the performance of steel and the use requirements of users, smelting the steel through a converter or an electric furnace, then refining the steel outside an LF furnace, smelting molten steel according with the chemical components of steel, stably controlling each chemical element, adopting high-performance refining synthetic slag, controlling the quantity and the form of various impurities in the steel, improving the purity of the steel, and then carrying out vacuum degassing treatment on the molten steel; remove harmful gases such as H and the like so as to meet the performance requirement of steel.

2) Continuous casting

The continuous casting billet is designed into a rectangular large billet, the section of the casting billet is 390mm x 510mm, the segregation of materials is controlled by adopting crystallizer electromagnetic stirring, tail end electromagnetic stirring and soft reduction, the floating adsorption of impurities is facilitated by adopting tundish induction heating, the pouring superheat degree can be controlled, and the pouring with low superheat degree is realized, so that the internal and surface quality of the casting billet is improved.

3) Cogging of continuous casting billet

Heating a blank by adopting a stepping heating furnace, selecting a corresponding heating system according to different steel types, taking the blank out of the furnace, descaling the surface of the blank by high-pressure water, rough rolling, and performing flame cleaning on the surface of the blank, wherein the flame cleaning is to spray high-pressure oxygen flow to the surface of the blank by fully distributing burners on the four sides of the rectangular blank, so that metal on the surface of the blank reacts with oxygen to instantly generate a large amount of heat, so that the metal on the surface of the blank is melted, the melted metal is taken away by the high-pressure oxygen flow to melt and cut the metal on the surface layer of the blank, a certain depth is removed from one side, usually 0.5-4mm, and the cleaning speed is 10-40 m/min; the defects of an oxide layer, a surface warping, folding, cracks and the like on the surface of the blank can be effectively removed by flame cleaning, so that good surface quality of the intermediate blank is obtained, and a foundation is laid for controlling surface decarburization and surface defects of a rolled material. After flame cleaning, finish rolling to the designed size of an intermediate billet, and controlling the compression ratio of cogging rolling to be 2-10; after the initial rolling, the steel plate is rolled into 250mm by 8 passes through a reciprocating rough rolling mill, after the rough rolling, the steel plate is cleaned by flame, and then the steel plate is rolled into 200mm by 200mm intermediate blanks through a 2-rack final rolling mill set. The cogging temperature is 1000-1150 ℃ during cogging rolling, and the finishing temperature is 800-950 ℃.

4) Flaw detection and grinding of intermediate blank

And (3) after cogging rolling is finished, putting the blank into a pit in time for slow cooling so as to prevent the intermediate blank from generating cracks, performing surface flaw detection on the intermediate blank after the slow cooling is finished, and grinding to remove the surface defects of the blank.

5) Intermediate blank rolling

Heating the blank in a stepping heating furnace, selecting corresponding heating systems according to different steel types, controlling the total heating time of the blank for controlling surface decarburization, wherein the total heating time is less than or equal to 4 hours, simultaneously controlling the heating temperature, the temperature of a soaking section is less than or equal to 1250 ℃, and ensuring that the total compression ratio of finished product rolling is more than or equal to 30. The method comprises the following steps of discharging a blank out of a furnace, performing surface high-pressure water descaling, then sequentially performing rough rolling → medium rolling → pre-finish rolling → KOCKS three-roller finish rolling to obtain a finished round steel, and specially designing a special pass with a finish rolling specification for controlling the dimensional tolerance of the finished product within +/-0.1 mm and the out-of-roundness less than or equal to 0.15mm, wherein the designed finish rolling pass is only used for rolling one specification.

6) Flaw detection of finished product

Due to the inherent characteristics of the hot rolled bar, the rolled bar inevitably has rolling defects, if the surface defects exceed a certain depth, the use is influenced, and the rolled bar cannot replace a bright silver bar, so the surface flaw detection of the rolled bar is needed, and the unqualified material subjected to flaw detection is scrapped or is repaired, repaired and qualified and then put in storage to ensure the surface quality of the material.

Compared with the prior art, the invention has the advantages that: the production method of the steel for the automobile shaft parts adopts a two-fire finished product, adopts a large-section rectangular blank during continuous casting to realize large compression ratio of cogging rolling and finished product rolling, and particularly controls the compression ratio of the finished product rolling to be more than or equal to 30 to control the depth of a decarburized layer of a hot rolled product. When the continuous casting billet is cogging-rolled, flame cleaning is adopted before finish rolling to remove surface defects of the billet, and oxide layers and harmful surface defects on the surface of the billet are fully removed. And carrying out surface flaw detection and finishing and coping on the intermediate blank to further remove the surface defects of the intermediate blank. And a KOCKS three-roller finish rolling is adopted during rolling of finished products, so that the non-roundness of the rolled material can meet the requirement. And finally, carrying out one hundred percent surface flaw detection on the rolled finished product to ensure that the surface defect depth of the finished product meets the requirement. By combining the method, the hot rolled material with shallow decarburized layer, high surface quality and high size precision can be produced to replace silvery processing, and the direct blanking and forming processing of customers is facilitated.

Drawings

FIG. 1 is a drawing of the appearance of an intermediate blank in the production method of steel for automobile shaft parts according to the present invention;

FIG. 2 is a picture of the appearance of a finished product in the production method of the steel for the automobile shaft parts.

Detailed Description

The present invention will be described in further detail with reference to examples.

The method for producing a steel material for automobile parts according to the present invention will be further explained and illustrated with reference to the drawings and the specific examples, which, however, should not be construed to unduly limit the technical scope of the present invention.

Example 1

The production method of the steel material for the automobile part in the embodiment 1 of the invention is manufactured according to the following procedures, and the steel material is specifically used for manufacturing a transmission shaft of a constant velocity universal joint (CVJ) of an automobile, the specification of the transmission shaft is phi 29mm, the part plays a role of transmission and support, in order to prevent lubricating fluid from leaking, a CVJ intermediate shaft and a soft outer sleeve need to be in good clearance fit, so that the surface decarburization of the material is required to be less than or equal to 0.1mm, the surface defect depth is less than or equal to 0.1mm, and the out-of-roundness is less than or equal to 0.15mm, a user directly performs blanking forming machine processing:

1) smelting: and (3) performing external refining after smelting in a 100-ton steel furnace, and performing vacuum degassing treatment on the molten steel, wherein the mass percentages of all chemical elements are strictly controlled according to requirements.

2) Continuous casting: continuously casting the mixture into a rectangular large square billet with the thickness of 390mm multiplied by 510mm, adopting a tundish for induction heating, and controlling the casting superheat degree of the tundish to be 10-40 ℃. In order to control the segregation of the material, advanced crystallizer electromagnetic stirring, tail end electromagnetic stirring, continuous casting and advanced equipment and process under soft pressure are adopted. The chemical composition percentages of the obtained continuous casting billets are shown in the following table 1:

table 1 (wt.%, balance Fe and other unavoidable impurity elements)

Steel grade	C	Si	Mn	S	P	Cr	Mo	Cu	B	O
											XC30	0.30	0.25	0.75	0.018	0.010	0.15	0.02	0.02	0.0025	0.0008

3) Continuous casting billet cogging (including flame cleaning): heating the blank in a stepping heating furnace for more than or equal to 4h, controlling the initial rolling temperature to be 1050-1200 ℃, discharging the blank out of the furnace, performing surface high-pressure water descaling and rough rolling, performing 8-pass rolling to 250mm by a reciprocating rough rolling machine after initial rolling, and cleaning by using flame after rough rolling. And (3) melting and cutting off the metal on the surface layer of the blank, removing 0.5-4mm of a single surface, and cleaning at a speed of 10-40 m/min. After flame cleaning, the blank is subjected to two times of finish rolling to be rolled into a designed 200 mm-200 mm intermediate blank, and the cogging rolling compression ratio is 5. After the intermediate billet is cut, the intermediate billet needs to be put into a pit and cooled as soon as possible, and the pit entering temperature is more than or equal to 500 ℃.

4) Intermediate blank grinding and flaw detection: and (3) carrying out 100% magnetic powder inspection on the 200 mm-200 mm intermediate blank, and then grinding the blank to remove the surface defects of the blank. The appearance of the intermediate blank is shown in figure 1.

5) Intermediate blank rolling

When the steel XC30 for the CVJ transmission shaft in the embodiment is rolled, a 200 mm-200 mm intermediate blank is adopted to be rolled into hot rolled round steel with the diameter of 29mm, the rolling ratio is 60, and when in finish rolling, the steel is finish rolled by using a KOCKS three-roller, and the specific finished product rolling process parameters are shown in the following table 2:

TABLE 2 (heating, hot rolling concrete process parameter table)

6) Flaw detection of finished product

Performing 100% surface flaw detection on the rolled stock, wherein the flaw detection standard is that the depth of surface defects is less than or equal to 0.1mm

And scrapping the damaged and unqualified materials, or grinding and re-probing the materials to be qualified and then warehousing the materials to ensure the surface quality of the materials.

The CVJ transmission shaft of example 1 was subjected to the key index test, and the test results are shown in table 3 below:

TABLE 3

As can be seen from table 3, the surface decarburization, the surface defect depth, and the dimensional accuracy in the examples completely satisfy the design requirements.

In conclusion, the XC30 hot rolled steel for the CVJ transmission shaft in the embodiment 1 has the advantages of shallow surface decarburized layer, high surface quality, high dimensional precision and good surface state, and can be directly processed by a blanking forming machine by a user as shown in FIG. 2.

It should be noted that the above examples are only specific embodiments of the present invention, and it is obvious that the present invention is not limited to the above embodiments, but many similar variations are possible as needed. All modifications which would occur to one skilled in the art and which are, therefore, directly derivable or suggested by the disclosure herein are to be included within the scope of the present invention.

Claims

1. A production method of automobile shaft part steel is characterized by comprising the following steps: the technological process includes smelting → continuous casting → cogging and rolling + scarfing → flaw detection and grinding of intermediate blank → rolling of intermediate blank → flaw detection of finished product, and the specific operations are as follows

1) Smelting

Designing corresponding chemical components according to the performance of steel and the use requirements of users, smelting the steel through a converter or an electric furnace, then refining the steel outside an LF furnace, smelting molten steel according with the chemical components of the steel, stably controlling all chemical elements, refining synthetic slag through high performance, and then carrying out vacuum degassing treatment on the molten steel;

2) continuous casting

The continuous casting blank is designed into a rectangular large square blank, the section of the casting blank is 390mm x 510mm, the segregation of the material is controlled by adopting crystallizer electromagnetic stirring, tail end electromagnetic stirring and soft reduction, the inclusion floats upwards and is adsorbed by adopting tundish induction heating, and the casting is protected by adopting low superheat degree;

3) cogging of continuous casting billet

Heating the blank by a stepping heating furnace, selecting a corresponding heating system according to different steel types, taking the blank out of the furnace, performing rough rolling after surface high-pressure water descaling, and rolling 8 times to 250mm by a reciprocating rough rolling mill after initial rolling; after rough rolling, carrying out flame cleaning on the surface of a blank, wherein the flame cleaning is to fully distribute burners on four sides of a rectangular blank, spraying high-pressure oxygen flow to the surface of the blank, reacting metal on the surface of the blank with oxygen to instantly generate a large amount of heat, so that the metal on the surface of the blank is melted, the melted metal is taken away by the high-pressure oxygen flow to melt and cut the metal on the surface layer of the blank, and the single surface is removed to a certain depth, usually 0.5-4mm, and the cleaning speed is 10-40 m/min; after flame cleaning, the mixture is rolled into an intermediate blank of 200mm x 200mm by a 2-frame final rolling unit; the cogging temperature is 1000-1150 ℃ during cogging rolling, the finishing temperature is 800-950 ℃, the intermediate billet is finely rolled into the designed size after being cleaned by flame, and the compression ratio of the cogging rolling is controlled between 2-10;

4) flaw detection and grinding of intermediate blank

After cogging rolling is finished, timely pit-dropping and slow cooling are carried out on the blank to prevent the intermediate blank from generating cracks, and after slow cooling is finished, surface flaw detection is carried out on the intermediate blank, and the surface defects of the blank are removed through grinding;

5) intermediate blank rolling

Heating the blank in a stepping heating furnace, selecting corresponding heating systems according to different steel types, controlling the total heating time of the blank for controlling surface decarburization, wherein the total heating time is less than or equal to 4 hours, and simultaneously controlling the heating temperature, the temperature of a soaking section is less than or equal to 1250 ℃, so that the total compression ratio of finished product rolling is ensured to be more than or equal to 30; the method comprises the following steps of (1) removing scale on the surface of a blank by high-pressure water after the blank is discharged from a furnace, and then sequentially carrying out rough rolling → medium rolling → pre-finish rolling → KOCKS three-roller finish rolling to obtain a finished round steel, wherein a special hole pattern with a finish rolling specification is designed for a bar in order to control the dimensional tolerance of the finished product within +/-0.1 mm and the out-of-roundness less than or equal to 0.15 mm;

6) flaw detection of finished product

And performing surface flaw detection on the rolled material, scrapping the material which is unqualified in flaw detection, or grinding and re-detecting the material to be qualified and then warehousing the material so as to ensure the surface quality of the material.