KR101655181B1 - High strength steel and method for manufacturing gear - Google Patents

Abstract

The high strength steel according to one embodiment of the present invention is characterized in that it contains 0.47 wt% or more and 0.53 wt% or less of C, 0.55 wt% or more and 0.65 wt% or less of Si, 0.85 wt% or more and 1.15 wt% or less of Mn, 0.020 wt% or more and 0.040 wt% or less, V: 0.08 wt% or more and 0.12 wt% or less, Al: 0.025 wt% or more and 0.045 wt% or less, B: 0.0010 wt% or more and 0.0050 wt% Includes unavoidable impurities.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a high-

High strength steel and gear manufacturing methods.

Recently, it has been required to increase the strength of materials in automobile parts and industrial machinery parts. Car gears have been manufactured using the carburizing heat treatment method, but they have a disadvantage in that they are vulnerable to thermal deformation when the gear is manufactured by the carburizing heat treatment method.

There is a method of manufacturing a gear by outline high frequency heat treatment in order to reduce thermal deformation. However, existing heavy carbon and heavy carbon based alloy steels are subject to deformation of the gear teeth due to the generation of flaws at the end of gear teeth during high-frequency heat treatment, resulting in additional machining and deterioration of durability.

Korean Patent Laid-Open No. 10-2009-0121308

One embodiment of the present invention is to provide a high strength steel.

Yet another embodiment of the present invention is to provide a gear manufacturing method.

The high strength steel according to one embodiment of the present invention is characterized in that it contains 0.47 wt% or more and 0.53 wt% or less of C, 0.55 wt% or more and 0.65 wt% or less of Si, 0.85 wt% or more and 1.15 wt% or less of Mn, 0.020 wt% or more and 0.040 wt% or less, V: 0.08 wt% or more and 0.12 wt% or less, Al: 0.025 wt% or more and 0.045 wt% or less, and B: 0.0010 wt% or more and 0.0050 wt% And inevitable impurities.

In addition, the values of [Formula 1] - [Formula 2] below may be 70 or more and 90 or less.

[Formula 1] = 910 - 203 [C] - 15.2 [Ni] +44.7 [Si] +104 [V] +31.5 [Mo] +13.1 [

[Formula 2] = 723 - 10.7 [Mn] - 16.9 [Ni] + 29.1 [Si] + 16.9 [Cr] + 290 [

Ni, Si, V, Ni, Si, V, Mo, W, Mn, Cr and As, Mo, W, Mn, Cr, and As.

0.08 wt% or less of Ni, 0.03 wt% or less of Mo, and 1.10 or less of Cr. The content of W and As depends on the content of the components incorporated in the steel by the steelmaking process.)

A method of manufacturing a gear according to an embodiment of the present invention includes the steps of: C: not less than 0.47 wt% and not more than 0.53 wt%, Si: not less than 0.55 wt% and not more than 0.65 wt%, Mn: not less than 0.85 wt% and not more than 1.15 wt% : 0.020 wt% or more and 0.040 wt% or less, V: 0.08 wt% or more and 0.12 wt% or less, Al: 0.025 wt% or more and 0.045 wt% or less, and B: 0.0010 wt% or more and 0.0050 wt% Fe and unavoidable impurities, followed by cooling; Secondary processing of the steel during or after the cooling is completed; And quenching the secondary processed steel material.

The quenching may be performed using a high frequency heat treatment at a temperature of 800 ° C or higher and 850 ° C or lower.

The secondary processing step is carried out at a temperature of 800 ° C or higher and 850 ° C or lower in the case of secondary processing during cooling and is carried out at a temperature not higher than the Ar ₁ transformation point when the steel is subjected to secondary processing after cooling is completed It can be one.

The secondary processing step may be forging, rolling, or rolling.

The primary processing step may be forging at a temperature of 1000 ° C or higher and 1250 ° C or lower.

The steel material may have a value of [Equation 1] - [Equation 2] below 70 or more and 90 or less.

[Formula 1] = 910 - 203 [C] - 15.2 [Ni] +44.7 [Si] +104 [V] +31.5 [Mo] +13.1 [

[Formula 2] = 723 - 10.7 [Mn] - 16.9 [Ni] + 29.1 [Si] + 16.9 [Cr] + 290 [

Ni, Si, V, Ni, Si, V, Mo, W, Mn, Cr and As, Mo, W, Mn, Cr, and As.

0.08 wt% or less of Ni, 0.03 wt% or less of Mo, and 1.10 or less of Cr. The content of W and As depends on the content of the components incorporated in the steel by the steelmaking process.)

After the quenching step, it may further comprise tempering.

The high strength steel according to one embodiment of the present invention has excellent workability and excellent strength.

Further, the method of manufacturing a gear according to an embodiment of the present invention is capable of manufacturing a gear of high strength and is excellent in durability. In addition, it is economical to perform heat treatment at a low temperature.

1 is a photograph showing a ring gear and a pinion gear manufactured according to an embodiment of the present invention.
Fig. 2 is a photograph showing a ring gear and a pinion gear manufactured using the component system of Comparative Example 1. Fig.
3 is a photograph showing a ring gear and a pinion gear that have been subjected to primary machining according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims. Like reference numerals refer to like elements throughout the specification.

Thus, in some embodiments, well-known techniques are not specifically described to avoid an undesirable interpretation of the present invention. Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Whenever a component is referred to as "including" an element throughout the specification, it is to be understood that the element may include other elements, not the exclusion of any other element, unless the context clearly dictates otherwise. Also, singular forms include plural forms unless the context clearly dictates otherwise.

The high strength steel according to one embodiment of the present invention is characterized in that it contains 0.47 wt% or more and 0.53 wt% or less of C, 0.55 wt% or more and 0.65 wt% or less of Si, 0.85 wt% or more and 1.15 wt% or less of Mn, 0.020 wt% or more and 0.040 wt% or less, V: 0.08 wt% or more and 0.12 wt% or less, Al: 0.025 wt% or more and 0.045 wt% or less, B: 0.0010 wt% or more and 0.0050 wt% Includes unavoidable impurities.

The high strength steel according to one embodiment of the present invention can be used for gears. More specifically, it can be used as an automotive gear.

C is an element that determines strength and hardness. If it is less than 0.47 wt%, strength and surface hardness may deteriorate. If it exceeds 0.53 wt%, forging workability and machinability are lowered.

Si is an element that is incorporated in the base and increases fatigue strength and high temperature softening resistance. If it is less than 0.55% by weight, the fatigue strength tends to be vulnerable to surface damage for heat. If it exceeds 0.65% by weight, hot forging and workability are deteriorated.

Mn serves as an austenite stabilizing element. Therefore, it is possible to perform a high-frequency heat treatment at a low temperature in manufacturing gears using steel according to one embodiment of the present invention. Further, the yield strength is improved by finely pulverizing pearlite and solidifying ferrite. It improves quenching and strength of steel, and increases calcination at high temperature to improve castability. In addition, MnS is formed in combination with S to prevent the red-hot brittleness and improve the cutting workability. When Mn is less than 0.85% by weight, the strength is weakened. When the Mn content is more than 1.15% by weight, MnS inclusions are excessively formed and the fatigue strength can be lowered.

S combines with Mn to form MnS, which improves cutting workability. If it is less than 0.020% by weight, machinability becomes insufficient. If it exceeds 0.040% by weight, FeS may be formed due to binding with Fe.

V improves the strength and toughness by refining the crystal grains by formation of fine carbonitride. If it is less than 0.08% by weight, the effect of increasing the strength is small, and if it is more than 0.12% by weight, the toughness may be deteriorated.

B promotes the formation of bainite structure and enhances the durability by improving the incombustibility. In addition, it is possible to delay precipitation of pro-eutectoid ferrite in a time-tempeature transformation diagram (TTT).

When the content of B is less than 0.001 wt%, the effect of addition is not exhibited. When the content of B is more than 0.005 wt%, oxides and nitrides are formed during the dissolving operation. When the steel having such a composition is heat-treated, boric carbide is formed, I can not.

Al acts as a deoxidizing agent and binds with N to refine the crystal grains. When the amount is less than 0.025% by weight, deoxidation or grain refining action can be reduced. When the amount exceeds 0.045% by weight, Al ₂ O ₃ And the like can have detrimental effects.

In addition, the steel according to an embodiment of the present invention may have a value of [Equation 1] - [Equation 2] of not less than 70 and not more than 90.

[Formula 1] = 910 - 203 [C] - 15.2 [Ni] +44.7 [Si] +104 [V] +31.5 [Mo] +13.1 [

[Formula 2] = 723 - 10.7 [Mn] - 16.9 [Ni] + 29.1 [Si] + 16.9 [Cr] + 290 [

Ni, Si, V, Ni, Si, V, Mo, W, Mn, Cr and As, Mo, W, Mn, Cr, and As)

When the value of [Equation 1] - [Equation 2] is less than 70, when the gear according to the embodiment of the present invention is used as a gear, it may cause a loss of hand or a durability. On the other hand, if it exceeds 90, the heat treatment temperature becomes high in the high frequency heat treatment and quenching treatment.

Also, the steel material may include 0.08 wt% or less of Ni, 0.03 wt% or less of Mo, and 1.10 or less of Cr. The content of W and As depends on the range of the contents of the steel in the steelmaking process.

Hereinafter, a method of manufacturing a gear using steel according to an embodiment of the present invention will be described. The gear according to an embodiment of the present invention may be an automotive gear.

The method of manufacturing a gear according to an embodiment of the present invention is a method of manufacturing a gear according to a preferred embodiment of the present invention. First, the gears are formed of at least 0.47 wt% and at most 0.53 wt% of C, at least 0.55 wt% and at most 0.65 wt% of Si, at least 0.85 wt% and at most 1.15 wt% , S: 0.020 wt% or more and 0.040 wt% or less, V: 0.08 wt% or more and 0.12 wt% or less, Al: 0.025 wt% or more and 0.045 wt% or less, B: 0.0010 wt% or more and 0.0050 wt% A steel material containing Fe and unavoidable impurities is provided.

The steel material may have a value of [Equation 1] - [Equation 2] of not less than 70 and not more than 90 in the steel material.

[Formula 1] = 910 - 203 [C] - 15.2 [Ni] +44.7 [Si] +104 [V] +31.5 [Mo] +13.1 [

[Formula 2] = 723 - 10.7 [Mn] - 16.9 [Ni] + 29.1 [Si] + 16.9 [Cr] + 290 [

Ni, Si, V, Ni, Si, V, Mo, W, Mn, Cr and As, Mo, W, Mn, Cr, and As.

Here, it may include not more than 0.08% by weight of Ni, not more than 0.03% by weight of Mo, and not more than 1.10% of Cr. The content of W and As depends on the content of the components incorporated in the steel by the steelmaking process)

The steel is first processed. The primary processing may be forging at a temperature of 1000 ° C or more and 1250 ° C or less. And is first processed to produce a predetermined part shape. The material that has undergone the first machining is cooled. The material is secondarily processed during the cooling or after the cooling is completed.

In the case of secondary processing during cooling, forging, rolling or rolling can be carried out at a temperature of 800 ° C or higher and 850 ° C or lower. When the steel is subjected to secondary processing after cooling is completed, it can be forged, rolled or rolled at temperatures below the Ar ₁ transformation point. When the secondary working is performed in the temperature range of the substrate, the bainite structure or the martensite structure can be made finer.

The quenched material is subjected to quenching. The quenching may be performed using a high frequency heat treatment at a temperature of 800 ° C or higher and 850 ° C or lower.

In general, the high-frequency heat treatment is performed at 900 ° C to 950 ° C. However, in the steel material component according to the embodiment of the present invention, the austenite region is wide and the high-frequency heat treatment can be performed at a temperature of 800 ° C or higher and 850 ° C or lower .

In addition, by performing the high-frequency heat treatment at a low temperature, it is possible to prevent the melting loss due to overheating and reduce the thermal deformation.

After the quenching is completed, the material may be subjected to a tempering heat treatment.

Hereinafter, the embodiment will be described in detail. The following examples are illustrative of the present invention only and are not intended to limit the scope of the present invention.

100 ton electric furnace, and the final Φ60, 100 round bar was manufactured through refining, vacuum degassing process and continuous casting process. The components of such a round bar are shown in Table 1.

The round bar was hot forged at 1130 ° C to produce a shape as shown in FIG. 3, and then subjected to secondary processing at 825 ° C during cooling to produce a ring gear and a pinion gear.

Thereafter, high-frequency heat treatment was performed at 830 캜, and tempering treatment was carried out at 150 캜 for 90 minutes in a heating furnace.

In the case of Comparative Example 1 and Comparative Example 2, the same high-frequency heat treatment as in the Examples was performed, and in Comparative Example 3, carburization heat treatment was performed after secondary processing.

division C Si Mn P S Cu Ni Cr Mo Al V B
(ppm) Weakness [Formula 1] - [Formula 2]
Axle durability
Test sum / fire Invention river 0.5 0.60 0.95 0.015 0.030 0.10 0.07 - 0.02 0.035 0.1 20 none 74 synthesis Comparative Example 1 0.5 0.30 0.70 0.015 0.032 0.10 0.07 - 0.02 0.038 0.1 20 Occur 66 - Comparative Example 2 0.5 0.50 0.95 0.015 0.025 0.10 0.07 - 0.02 0.035 - 20 none 62 fire Comparative Example 3 0.2 0.25 0.85 0.020 0.020 0.15 0.07 1.00 - - - - - 92 -

In Table 1,

[Formula 1] = 910 - 203 [C] - 15.2 [Ni] +44.7 [Si] +104 [V] +31.5 [Mo] +13.1 [

[Formula 2] = 723 - 10.7 [Mn] - 16.9 [Ni] + 29.1 [Si] + 16.9 [Cr] + 290 [As] + 6.38 [W].

In addition, the axle endurance test is performed in the state of axle gear assembly, and it is judged that the test is stopped due to surface damage or gear breakage during the test with the acceptance criterion of 250,000 cycles, or if there is surface damage after the test.

The deformation amounts of Examples and Comparative Example 3 were measured and are shown in Table 2.

division Ring gear deformation (mm) Pinion gear deformation (mm) Tooth eccentricity Back Runout shake torsion Squareness Tooth eccentricity Comparative Example 3 Invention river Comparative Example 3 Invention river Comparative Example 3 Invention river Comparative Example 3 Invention river Comparative Example 3 Invention river Comparative Example 3 Invention river 5
medium 0.04 0.024 0.038 0.01 0.04 0.022 0.048 0.024 0.004 0.004 0.05 0.031

Fig. 1 is a photograph showing a ring gear and a pinion gear manufactured according to an embodiment of the present invention, and Fig. 2 is a photograph showing a ring gear and a pinion gear manufactured using the component system of Comparative Example 1. Fig.

Referring to FIGS. 1 and 2, it can be seen that no malfunction occurred in the gear according to the embodiment of the present invention, but malfunction occurred in the case of the comparative example 1.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims (9)

C: not less than 0.47 wt% and not more than 0.53 wt%, Si: not less than 0.55 wt% and not more than 0.65 wt%, Mn: not less than 0.85 wt% and not more than 1.15 wt%, S: not less than 0.020 wt% 0.08 wt% or more and 0.12 wt% or less, Al: 0.025 wt% or more and 0.045 wt% or less, and B: 0.0010 wt% or more and 0.0050 wt% or less with the balance being a high strength steel containing Fe and unavoidable impurities ,
A high strength steel having a value of [Formula 1] - [Formula 2] of not less than 70 and not more than 90.
[Formula 1] = 910 - 203 [C] - 15.2 [Ni] +44.7 [Si] +104 [V] +31.5 [Mo] +13.1 [
[Formula 2] = 723 - 10.7 [Mn] - 16.9 [Ni] + 29.1 [Si] + 16.9 [Cr] + 290 [
Ni, Si, V and As are respectively represented by the following formulas: [C], [Ni], [Si], [V], [Mo], [W], [Mn], [Cr] , Mo, W, Mn, Cr, and As.
0.08 wt% or less of Ni, 0.03 wt% or less of Mo, and 1.10 or less of Cr. The content of W and As depends on the content of the components incorporated in the steel by the steelmaking process.)
delete C: not less than 0.47 wt% and not more than 0.53 wt%, Si: not less than 0.55 wt% and not more than 0.65 wt%, Mn: not less than 0.85 wt% and not more than 1.15 wt%, S: not less than 0.020 wt% 0.08 wt% or more and 0.12 wt% or less, Al: 0.025 wt% or more and 0.045 wt% or less, and B: 0.0010 wt% or more and 0.0050 wt% or less and the remainder being Fe and unavoidable impurities Cooling and cooling;
Secondary processing of the steel during or after the cooling is completed; And
And a step of quenching the secondary processed steel material,
Wherein the steel material has a value of [Expression 1] - [Expression 2] below 70 or more and 90 or less.
[Formula 1] = 910 - 203 [C] - 15.2 [Ni] +44.7 [Si] +104 [V] +31.5 [Mo] +13.1 [
[Formula 2] = 723 - 10.7 [Mn] - 16.9 [Ni] + 29.1 [Si] + 16.9 [Cr] + 290 [
Ni, Si, V and As are respectively represented by the following formulas: [C], [Ni], [Si], [V], [Mo], [W], [Mn], [Cr] , Mo, W, Mn, Cr, and As.
0.08 wt% or less of Ni, 0.03 wt% or less of Mo, and 1.10 or less of Cr. The content of W and As depends on the content of the components incorporated in the steel by the steelmaking process.)
The method of claim 3,
Wherein the quenching step uses a high frequency heat treatment at a temperature of 800 DEG C or more and 850 DEG C or less.
5. The method of claim 4,
The secondary processing step is performed at a temperature of 800 ° C or higher and 850 ° C or lower when the steel is subjected to secondary processing during cooling,
Wherein the steel is subjected to secondary working after cooling is completed, at a temperature not higher than Ar ₁ transformation point.
6. The method of claim 5,
Wherein said secondary machining step is performed by forging, rolling, or rolling.
5. The method of claim 4,
Wherein said primary machining step is performed at a temperature of not less than 1000 캜 and not more than 1250 캜.
delete The method of claim 3,
Further comprising tempering after said quenching step.

Images