KR101705168B1 - Carburizing alloy steel improved durability and the method of manufacturing the same - Google Patents

Abstract

The present invention relates to a carburized alloy steel having improved durability and a method of producing the same. More particularly, the present invention relates to a carburized alloy steel containing iron (Fe) as a main component and 0.1 to 0.35% by weight of carbon (C) (Mo), 0.1 to 0.6 wt% of nickel (Ni), 0.1 to 1.5 wt% of manganese (Mn), 0.5 to 1.5 wt% of chromium (Cr), 0.2 to 0.5 wt% of molybdenum More than 0 wt% to 0.07 wt% or less of vanadium (V), more than 0 wt% to 0.5 wt% or less of vanadium, 0 wt% to 0.5 wt% (B) 0.00002 to 0.00005 wt%, tungsten (W) more than 0 wt% and not more than 0.4 wt%, zirconium (Zr) more than 0 wt% to not more than 0.01 wt%, cobalt (Co) Y) exceeding 0% by weight and not more than 2% by weight, the carburized alloy steel has the effect of improving durability such as hardness, strength, toughness, fatigue strength and fatigue life, It enables a high strength alloy steel, such as via the weight of the thinning and about 20%, to secure the degree of freedom in vehicle design and, to a carburizing alloy steel and a method that is effective to reduce the manufacturing costs.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a carburized alloy steel having improved durability,

The present invention relates to a carburized alloy steel having improved durability and a method of manufacturing the same. More particularly, the present invention relates to a carburized alloy steel having improved durability, and more particularly, to an alloy steel having excellent properties such as hardness, strength, toughness, fatigue strength, To a carburized alloy steel and a method of manufacturing the same.

Recently, environmental problems are emerging all over the world, and in order to cope with such problems in the whole industry, a method of saving fuel is being sought. In order to achieve fuel savings, the solution proposed in the field of automobile industry is to improve the efficiency of the automobile engine and reduce the weight of the automobile. If the vehicle is lightened, it can be a good measure to increase the fuel efficiency of the car. However, if the weight of the vehicle is reduced, the strength and durability required of the vehicle can not be satisfied. Therefore, solving this problem is becoming a major goal of the automobile industry.

Accordingly, the automobile industry is developing a variety of eco-friendly vehicles aiming to reduce carbon dioxide emissions to 95% of the current level, or 27%, by 2021. In addition, to meet the US Corporate Average Fuel Economy (CAFE) of 54.5 mpg (23.2 km / l) in 2025, automakers are committed to developing downsizing and fuel efficiency technologies.

Generally, the material is made lighter in order to cope with an increase in the number of parts or an increase in weight. At this time, a method of lighter weight is used to increase the strength of the material or heat treatment technique for hardening the surface of the material. In addition, precision joining, low-deformation welding, and low-deformation heat treatment techniques are used to cope with the complicated shape of parts. In addition to this, technology to reduce deformation due to heat treatment and noise reduction and damping technology are used to reduce noise.

Especially, we are developing high performance and high efficiency technology of engine and transmission to maximize fuel efficiency of automobile. This technology is applied to high efficiency of multi-shoe, new concept oscillator and two-pump system, fusion hybrid technology, automatic / manual fusion transmission and hybrid transmission technology And the like.

The alloy steel used in the engine and the transmission related technology is used in parts of engines, transmissions, carriers, gears, shafts and synchro hubs. The alloy steel is used at 32-40% of the engine weight, Which is about 58 to 62% by weight. Particularly, gears and the like of a transmission are required to have a high strength and a high durability due to a demand for weight reduction and downsizing. However, the technology related to the downsizing and the improvement of the fuel economy has a problem of increasing the load applied to the engine parts and deteriorating the quality of parts and durability life due to sintering, friction and wear.

In general, the gears of an automobile transmission are used to transmit engine power directly to a differential system, and to transmit the power of the engine efficiently between two or more axes according to the running condition of the vehicle And receives bending stress and contact stress at the same time. When the durability of the material is insufficient in the gear flow, fatigue damage (fitting) due to lack of bending fatigue strength (tooth break) and contact fatigue strength due to insufficient bending fatigue strength is generated. Therefore, the gears require high physical properties such as hardness, strength, toughness, fatigue strength, and fatigue life.

As an alternative to such a demand, the present invention provides a method of manufacturing a carbon steel sheet which comprises 0.17-0.23% by weight of carbon (C), 0.5-0.7% by weight of silicon (Si), 0.45-0.75% by weight of manganese (Mn) Carburized steel such as SCM820PRH containing 0.015 to 0.035% by weight of ribbednon (Mo) and 0.0015% by weight of oxygen (O2) is used. However, such carburized steel has a problem in that the above-mentioned tooth-cutting and fitting are liable to occur.

Accordingly, the present inventor has sought to develop a carburized alloy steel having improved physical properties such as hardness, strength, toughness, fatigue strength and fatigue life, and a method for producing the same.

Japanese Laid-Open Patent Publication No. 11-323487 Japanese Unexamined Patent Application Publication No. 2003-328078 Japanese Patent No. 5,262,740 Japanese Patent No. 5,098,486

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a method of manufacturing a semiconductor device, which comprises the steps of depositing carbon, silicon, manganese, chromium, molybdenum, (V), nickel (Ni), titanium (Ti), nitrogen (N), boron (B), tungsten (W), zirconium (Zr), cobalt (Co), and yttrium Hardness, strength, toughness and the like, thereby improving durability and a method for producing the same.

According to the present invention for solving the problems of the prior art described above, it is preferable that 0.1 to 0.35% by weight of carbon (C), 0.1 to 2.0% by weight of silicon (Si) (Ni), 0.1 to 1.5 wt% of manganese (Mn), 0.5 to 1.5 wt% of chromium (Cr), 0.2 to 0.5 wt% of molybdenum (Mo), more than 0 wt% 0.1 to 0.6% by weight of vanadium, 0 to 0.5% by weight of vanadium, 0 to 0.5% by weight of titanium, 0 to 0.115% By weight to 0.00005% by weight.

In addition, the carburized alloy steel of the present invention further includes tungsten (W), wherein tungsten (W) is preferably 0 wt% or more and 0.4 wt% or less.

Further, the carburized alloy steel according to the present invention may further include zirconium (Zr), and it is preferable that the zirconium (Zr) is more than 0 wt% and 0.01 wt% or less.

In addition, the carburized alloy steel according to the present invention further includes cobalt (Co), and it is preferable that cobalt (Co) is not less than 0 wt% and not more than 5 wt%.

In addition, the carburized alloy steel of the present invention further includes yttrium (Y), wherein yttrium (Y) is preferably more than 0 wt% and less than 2 wt%.

Further, the carburized alloy steel according to the present invention may further include at least one of tungsten (W), zirconium (Zr), cobalt (Co), and yttrium (Y) (Co) is not less than 0 wt% and not more than 5 wt%, and the yttrium (Y) is not less than 0 wt% and not more than 2 wt%, and the zirconium (Zr) .

According to another aspect of the present invention, there is provided a method of manufacturing a carburized alloy steel, comprising the steps of: mixing a material of the carburized alloy steel; Carburizing the alloy steel at 930 to 980 캜 for 1.6 to 4 hours; Oiling the carburized heat-treated alloy steel to 80 to 120 ° C; And tempering the oil-refined alloy steel at 150 to 200 DEG C for 1 to 3 hours.

According to an aspect of the present invention, there is provided an automotive transmission manufactured using the carburized alloy steel.

(C), silicon (Si), manganese (Mn), chromium (Cr), molybdenum (Mo), niobium (Nb), and niobium (Nb) Carburized alloy steels and carburizations containing vanadium (V), nickel (Ni), titanium (Ti), nitrogen (N), boron (B), tungsten (W), zirconium (Zr), cobalt (Co) The alloy steel manufacturing method has an effect of improving durability such as hardness, strength, toughness, fatigue strength and fatigue life of the material. Further, it is possible to increase the strength of the carburized alloy steel, to reduce the thickness of the steel and to reduce the weight of the steel by about 20%, thereby securing the degree of freedom of automobile design and reducing the manufacturing cost.

According to the automotive transmission manufactured using the carburized alloy steel of the present invention, it is possible to increase the durability of the vehicle and reduce the weight of the automobile, thereby increasing the fuel consumption and preventing environmental pollution.

Hereinafter, preferred embodiments of the present invention will be described in detail. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be interpreted in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, it should be understood that the embodiments described herein are merely the most preferred embodiments of the present invention and are not intended to represent all of the technical ideas of the present invention, so that various equivalents and modifications It should be understood.

Hereinafter, the present invention will be described in detail. TECHNICAL FIELD The present invention relates to a carburized alloy steel having improved durability and a method of manufacturing the same, and in one aspect the present invention relates to a carburized alloy steel having improved durability.

The carburized alloy steel having improved durability according to the present invention contains 0.1 to 0.35% by weight of carbon (C), 0.1 to 2% by weight of silicon (Si), 0.1 to 2% by weight of manganese (Mn) 0.5 to 1.5% by weight of chromium (Cr), 0.2 to 0.5% by weight of molybdenum (Mo), 0.1 to 0.6% by weight of nickel, 0 to 0.07% by weight of niobium (Nb) More than 0 wt% and not more than 0.5 wt% of vanadium (V), more than 0 wt% and not more than 0.5 wt% of titanium (Ti), more than 0 wt% and less than 0.015 wt% of nitrogen (N), and 0.00002 to 0.00005 wt% .

In addition, the present invention can be used in an amount of more than 0 wt% to 0.4 wt% or less of tungsten (W), more than 0 wt% and less than 0.01 wt% of zirconium (Zr) (Y) more than 0% by weight and 2% by weight or less.

More specifically, the reasons for limiting the numerical values of the components constituting the carburized alloy steel according to the present invention are as follows.

(1) 0.1 to 0.35% by weight of carbon (C)

The carbon (C) is the most intrusive matrix strengthening element among the chemical components. It forms a carbide by bonding with an element such as chromium (Cr) to improve strength and hardness, increases the surface hardness during carburizing, It is also responsible for creating.

For such a role, the carbon (C) content is preferably about 0.1 to 0.35% by weight based on the weight of the entire alloy steel. When the content of carbon (C) is less than about 0.1% by weight, the strength of the alloy steel is lowered, and hardness due to carburization may be difficult to secure. On the other hand, when the content of carbon (C) is more than about 0.35% by weight, the core hardness of the alloy steel is increased due to excessive carburization, and the toughness of the entire alloy steel is deteriorated.

(2) 0.1 to 2% by weight of silicon (Si)

Although silicon (Si) plays a role of inhibiting carburization when added in excess, silicon (Si) inhibits the formation of pinholes in alloy steel as a deoxidizer and increases the strength of alloy steel by solid- .

For such a role, the content of silicon (Si) is preferably about 0.1 to 2.0 wt% with respect to the weight of the entire alloy steel. If the content of silicon (Si) is less than about 0.1 wt%, the effect of deoxidizing agent hardly occurs. On the other hand, when the content of silicon (Si) is greater than about 2.0 wt% There is a problem that moldability and needle-like elasticity are deteriorated.

(3) Manganese (Mn) 0.1 to 1.5 wt%

The manganese (Mn) serves to improve the ingotability of the alloy steel and the strength of the alloy steel. For such a role, the content of manganese (Mn) is preferably about 0.1 to 1.5% by weight.

If the content of manganese (Mn) is less than about 0.1% by weight, sufficient entanglement can not be ensured. On the other hand, when the content of manganese (Mn) exceeds about 1.5% by weight, And the mechanical properties of the alloy steel are deteriorated.

(4) 1.5 to 3.0 wt% of chromium (Cr)

The chromium (Cr) improves the ingotability of the alloy steel, gives the hardenability, makes the structure of the alloy steel finer, reacts with carbon (C) to form fine carbides to promote carburization, . Further, the formation of precipitated carbide and cementite is enhanced.

For such a role, the content of chromium (Cr) is preferably about 1.5 to 3.0% by weight. When the content of chromium (Cr) is less than about 1.5 wt%, the effect of forming carbide is reduced. When the content of chromium (Cr) is more than about 3.0 wt%, the toughness of the alloy steel is lowered, There is a problem that an increase in the production cost is caused due to an insufficient effect due to an increase in the content.

(5) 0.2 to 0.5% by weight of molybdenum (Mo)

The molybdenum (Mo) increases carbide formation, increases stability at high temperatures, and decreases carbon activity. In addition, it improves hardenability and toughness of alloy steel after alloying and tempering, and plays a role of imparting brittle resistance.

For such a role, the content of the molybdenum (Mo) is preferably about 0.2 to 0.5% by weight. If the content of the molybdenum (Mo) is less than about 0.2 wt%, the hardenability and toughness of the alloy steel can not be sufficiently secured. On the other hand, when the content of molybdenum (Mo) exceeds about 0.5 wt% , There is a problem that the processability (machinability) and productivity of the alloy steel deteriorate.

(6) From 0 to less than 0.07% by weight of niobium (Nb)

The niobium (Nb) binds with nitrogen to form nitrides and the like to refine the crystal grains, increase the recrystallization temperature and facilitate high-temperature carburization, thereby improving the hardenability and toughness of the alloy steel. For such a role, the content of niobium (Nb) is preferably more than 0 wt% and not more than about 0.07 wt%.

When the content of niobium (Nb) is more than about 0.07% by weight, the effect of niobium (Nb) is not only saturated but also toughness, workability and productivity are deteriorated. On the other hand, when the niobium (Nb) is not included, it is difficult to perform the carburization process at a high temperature.

(7) 0% by weight or more and 0.3% by weight or less vanadium (V)

The vanadium (V) forms a precipitate such as carbide and enhances the strength of the base structure, the strength and the wear resistance of the base structure through the precipitation strengthening effect, and refines the crystal grains. It also serves to reduce the activity of carbon.

For such a role, the vanadium (V) content is preferably more than 0 wt% and not more than about 0.3 wt%. If the content of vanadium (V) exceeds about 0.3 wt%, the toughness and hardness of the alloy steel may be lowered.

(8) more than 0% by weight and less than 0.5% by weight of titanium (Ti)

The titanium (Ti) plays a role of suppressing the growth of crystal grains by forming carbonitride and improving high-temperature stability, strength and toughness.

For such a role, the content of titanium (Ti) is preferably more than 0 wt% and not more than about 0.5 wt%. If the content of titanium (Ti) exceeds about 0.5% by weight, coarse precipitates are formed, and the low-temperature impact resistance is lowered and the manufacturing cost is increased due to saturation of the effect.

(9) more than 0% by weight of nitrogen (N) and not more than 0.015% by weight

The nitrogen (N) serves to stabilize austenite, fine grain, and improve the tensile strength, yield strength and elongation of the alloy steel. However, durability may be degraded due to the formation of impurities. For such a role, the content of nitrogen (N) is preferably more than 0 wt% and not more than 0.015 wt%.

Here, when the content of nitrogen (N) is about 0.015 wt% or less, there is a problem that brittleness may be caused and durability life may be lowered.

(10) Boron (B) 0.00002 to 0.00005 wt%

The boron (B) serves to improve hardenability, tensile strength, impact resistance and strength of the alloy steel and to prevent corrosion. However, there is a problem that the weldability deteriorates.

For this purpose, the content of the boron (B) is preferably about 0.00002 to 0.00005% by weight. When the content of boron (B) is less than about 0.00002 wt%, it is difficult to secure sufficient hardenability of the alloy steel. On the other hand, when the content of boron (B) exceeds about 0.00005 wt%, toughness and ductility There is a problem that the impact resistance is lowered.

(11) 0.1 to 0.6% by weight of nickel (Ni)

The nickel (Ni) serves to improve heat resistance and toughness. For such a role, the content of nickel (Ni) is preferably about 0.1 to 0.6% by weight.

If the content of nickel (Ni) is less than about 0.1 wt%, sufficient heat resistance and toughness can not be secured. On the other hand, when the content of nickel (Ni) exceeds about 0.6 wt%, the workability (machinability) And productivity are deteriorated.

(12) tungsten (W) more than 0 wt% and not more than 0.4 wt%

The tungsten forms a precipitated carbide to improve abrasion resistance and toughness at a high temperature. However, it plays a role of suppressing the growth of the tissue and reducing the scale resistance.

Therefore, for proper function of the tungsten, it is preferable that the content of the tungsten is more than 0 wt% and 0.4 wt% or less. If the content of tungsten exceeds 0.4% by weight, the formation of precipitated carbides becomes excessive and the toughness is lowered.

(13) Zirconium (Zr) more than 0 wt% and not more than 0.01 wt%

The zirconium serves to extend precipitates and remove nitrogen (N), oxygen (O), and sulfur (S), but also acts to reduce the size of non-metallic seal materials.

Therefore, it is preferable that the zirconium content is more than 0 wt% and 0.01 wt% or less. If the content of zirconium exceeds 0.01% by weight, ZnO2 is formed and the production cost due to saturation of the effect of zirconium is increased.

(14) Cobalt (Co) more than 0 wt% and not more than 5 wt%

The cobalt suppresses grain growth at a high temperature, and the ingotability is increased. In addition, the temperature is increased and the strength is maintained, thereby increasing the abrasion resistance. In addition, it contributes to improvement of processability. However, the cobalt is an element that does not form carbide and is an element that is not related to corrosion resistance.

Therefore, it is preferable that the cobalt is more than 0 wt% and not more than 5 wt%. If it exceeds 5% by weight, the role of the element forming the carbide is lowered, and the effect is saturated, thereby increasing the manufacturing cost.

(15) more than 0% by weight and less than 2% by weight of yttrium (Y)

The yttrium is an element that increases stability at high temperature, and improves the heat resistance and toughness at high temperature, and forms an impermeable barrier oxide surface that prevents oxidation and corrosion when exposed to high temperatures. Further, the resistance to sintering and chemical resistance is excellent.

Therefore, it is preferable that the yttrium is more than 0 wt% and not more than 2 wt%. If the content of yttrium is more than 2% by weight, it interferes with the role of the other element, and the weldability decreases and the manufacturing cost increases.

The carburized alloy steel according to the present invention having such a constitution is excellent in hardness, strength, toughness, fatigue strength, fatigue life and the like, and is preferably applied to automobile parts and the like, more preferably applied to an automatic or manual transmission, Among them, it is most preferable to be applied to a carrier, an annulus gear, a gear, a shaft type or a synchro hub.

Hereinafter, from another viewpoint, the present invention relates to a method of manufacturing a carburized alloy steel having improved durability.

Carburized alloy steels having improved durability according to the present invention can be suitably manufactured by those skilled in the art with reference to known techniques. More particularly, the present invention provides a method of manufacturing a carburized alloy steel having improved durability, comprising the steps of: mixing the material of the carburized alloy steel; Carburizing the alloy steel at about 930 to 980 캜 for about 1.6 to 4 hours; Oiling the carburized heat-treated alloy steel to about 80 to 120 캜; And tempering the oil-quenched alloy steel at about 150-200 [deg.] C for about 1-3 hours; And the like.

As described above, the step of mixing the material for the carburizing alloy steel may be carried out by mixing carbon, silicon, manganese, chromium, molybdenum, niobium, vanadium, (W), zirconium (Zr), cobalt (Co), and yttrium (Y) is added to the metal (V), nickel (Ni), titanium (Ti), nitrogen It can be further mixed.

When the heat treatment temperature is less than about 930 ° C., the heat treatment time is increased and the productivity is reduced. When the heat treatment time is less than about 1.6 hours, the time during which carbon (C) is supplied, There is a problem that the carburization is not sufficient.

On the other hand, when the heat treatment temperature is higher than about 980 DEG C, recrystallization of the alloy steel may cause deterioration of mechanical properties. If the heat treatment time is more than about 4 hours, , There is a problem that the manufacturing cost increases.

When the oil quenching temperature is less than about 80 캜 or the tempering temperature is less than about 150 캜 in the oil quenching step, it may be difficult to secure the toughness of the alloy steel due to the formation of residual austenite, If the tempering time is less than about 1 hour, the embrittlement is not relieved, the material deviation becomes worse, and it becomes difficult to secure toughness.

On the other hand, when the oil quenching temperature is higher than about 120 ° C. or the tempering temperature is higher than about 200 ° C., the fatigue characteristics of the alloy steel are lowered due to an increase in retained austenite during the quenching process, In the case of exceeding 3 hours, it may be difficult to improve the durability life due to a decrease in hardness of the alloy steel.

Hereinafter, from another viewpoint, the present invention relates to an automotive transmission manufactured using a carburized alloy steel having improved durability.

The automotive transmission manufactured using the carburized alloy steel having improved durability according to the present invention can be suitably manufactured by those skilled in the art with reference to known techniques. More specifically, when manufacturing the automotive transmission using the carburized alloy steel, it is possible to increase the strength of the material, to reduce the thickness of the automobile transmission, and to reduce the weight of the automobile by about 20% There is an effect. Accordingly, it is possible to increase the durability of the vehicle and to reduce the weight of the automobile, thereby increasing the fuel consumption and preventing environmental pollution.

[Example]

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are merely illustrative of the present invention and that the scope of the present invention is not construed as being limited by these embodiments.

In order to compare the physical properties of the carburized alloy steels according to the present invention, the carburizing temperature and time, the temperature of the quenching oil, the tempering temperature and the time conditions as shown in Table 2 below were applied Examples and Examples were prepared.

division unit Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Example 1 Example 2 Example 3 Example 4 C weight% 0.19 0.20 0.22 0.34 0.17 0.33 0.18 0.29 0.19 Si weight% 0.63 0.62 0.63 0.52 1.85 0.55 1.86 0.54 1.78 Mn weight% 0.65 0.61 0.58 0.71 1.21 0.78 1.23 0.75 1.22 Cr weight% 2.06 3.64 3.73 1.34 0.61 1.38 0.63 1.22 0.86 Ni weight% - - - 0.15 0.57 0.12 0.59 0.17 0.69 Mo weight% 0.38 - 0.16 0.23 0.44 0.21 0.47 0.24 0.48 Nb weight% 0.029 0.026 0.025 0.024 0.067 0.022 0.066 0.026 0.064 V weight% - - - 0.16 0.44 0.13 0.47 0.15 0.44 Ti weight% - 0.0018 - 0.15 0.45 0.18 0.46 0.19 0.45 B weight% - 0.013 - 0.000013 0.000042 0.000046 0.000026 0.000046 0.000025 N weight% 0.0076 0.0067 0.0083 0.0067 0.0062 0.006 0.0053 0.006 0.0053 W weight% - - - 0.21 0.13 0.22 0.15 0.25 0.35 Zr weight% - - - 0.003 0.005 0.004 0.007 0.005 0.006 Co weight% - - - 5.15 - - - 4.92 - Y weight% - - - - 2.13 - - - 1.86

Table 1 is a table comparing the constituent components and contents of Comparative Examples 1 to 3 according to conventional alloy steels and the constituent components and compositions of Examples 1 and 2 according to the present invention.

Table 2 is a table comparing the carburization temperature and time, the temperature of the quenching oil, and the tempering temperature and time in the manufacturing conditions of Comparative Examples 1 to 3 having the constituents and contents in Table 1 and Examples 1 and 2 . Herein, in Comparative Examples 1 to 3 and Examples 1 and 2, the carburization temperature and time, the temperature of the quenching oil, and the tempering temperature and time according to the present invention were satisfied.

Table 3 shows the surface hardness, the depth hardness, the tensile strength, the yield strength, the carburization depth, the tensile strength, the tensile strength, the tensile strength, and the tensile strength after the Comparative Examples 1 to 3 and the Examples 1 and 2, The impact strength, the rotational bending strength, the contact fatigue life, the precipitate fraction and the martensite fraction.

The surface hardness and core hardness were measured using a micro Vickers hardness meter according to the KS B 0811 measurement method and the rotational bending strength was measured according to KS B ISO 1143 using a maximum flexural moment of about 20 kgfm and a rotation speed of about 200 to 3000 RPM , A maximum load of about 100 kg, and an electric three-phase, 220 V, and 7 kW, using a standard wire diameter of about 4 mm in diameter, using a rotary bending fatigue tester.

The L10 lifetime is the rated fatigue life of the specimen, which means the total number of revolutions of the rotational bending fatigue tester until about 10% of the specimen is damaged. The contact fatigue was measured using a contact fatigue tester under the conditions of a surface pressure of about 332 kg / mm 2, a lubricating oil temperature of about 80 캜, and a lubricating oil amount of about 1.2 l / min until the cracks freeze on the specimen. Were measured.

In the case of surface hardness and core hardness, Examples 1, 2, 3 and 4 exhibited higher values than Comparative Examples. In the case of tensile strength and yield strength, the values of Examples were higher than those of Comparative Examples. The depth of the carburization was not only deeper than that of the comparative example but also the impact value, the rotational bending strength and the contact fatigue life were also improved as compared with the comparative example. It is also confirmed that the fraction of the precipitate and the martensite are both improved.

The tensile strength and the yield strength are about 5%, the carburizing depth is about 7%, the impact value is about 52%, the rotation speed is about 10%, the core hardness is about 12% The bending strength was about 24% and the contact fatigue life was about 72%.

Although the present invention has been described in connection with the specific embodiments of the present invention, it is to be understood that the present invention is not limited thereto. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents. Various modifications and variations are possible.

Claims (13)

(C), 0.1 to 2.0% by weight of silicon (Si), 0.1 to 1.5% by weight of manganese (Mn), 0.1 to 1.5% by weight of chromium (Cr) 0.5 to 1.5 wt% of molybdenum (Mo), 0.2 to 0.5 wt% of molybdenum (Mo), 0 to 0.07 wt% of niobium (Nb), 0.07 wt% or less of nickel, 0.1 to 0.6 wt% (B) 0.00002 to 0.00005 wt.%, Tungsten (W) in excess of 0 wt.% And 0.4 wt.% Or less, Or less and zirconium (Zr) in an amount of more than 0 wt% to 0.01 wt% or less.
delete delete delete delete delete The method according to claim 1,
And more than 0 wt% and not more than 5 wt% of cobalt (Co).
delete The method according to claim 1,
Further comprising 0% by weight or more and 2% by weight or less of yttrium (Y).
delete The method according to claim 1,
Wherein the cobalt (Co) content is more than 0 wt% and not more than 5 wt%, and yttrium (Y) is more than 0 wt% and not more than 2 wt%.
Mixing the material of the carburized alloy steel of any one of claims 1, 7, 9, and 11;
Carburizing the alloy steel at 930 to 980 캜 for 1.6 to 4 hours;
Oiling the carburized heat-treated alloy steel to 80 to 120 ° C; And
And tempering the oil-refined alloy steel at 150 to 200 DEG C for 1 to 3 hours.
11. An automotive transmission made of carburized alloy steel according to any one of claims 1, 7, 9 and 11.