DE102015220195A1 - Carburized alloy steel with improved durability and method of making the same - Google Patents

Abstract

A carburized alloy steel comprises, based on the total weight of the alloy steel, 0.1 to 0.35% by weight of carbon (C), 0.1 to 2% by weight of silicon (Si), 0.1 to 1.5% by weight % of manganese (Mn), 3 to 5.5% by weight of chromium (Cr), 0.2 to 0.5% by weight of molybdenum (Mo), 0 to 0.07% by weight of niobium (Nb ), 0 to 0.3% by weight of vanadium (V), 0 to 0.2% by weight of titanium (Ti), 0 to 0.015% by weight of nitrogen (N), 0.002 to 0.005% by weight of boron (B) and a balance of iron (Fe). A method for producing the same is also disclosed.

Description

Reference to related applications

This application claims the priority of Korean Patent Application No. 10-2014-175183 filed on 8 December 2014 with the Korean Patent Office, the disclosure of which is hereby incorporated by reference in its entirety.

Technical area

The present invention relates to a carburized alloy steel (also referred to as carburized alloy steel) having improved durability and a method for producing the same, and more particularly a carburized alloy steel having a suitable forming component and suitable forming content, for effective durability to effect carburization on a surface of the alloy beam, and thus to improve the hardness, strength, ruggedness, fatigue strength, durability, and the like, and a method for producing the same.

State of the art

In the automotive industry, various environmentally friendly vehicles aimed at reducing the emission of carbon dioxide to 95 g / km, which is a reduction of 27% compared to a current amount, are developed according to European directives by 2021. Further, vehicle manufacturers are striving to develop technology to reduce engine size and improve fuel economy to reach 23.2 km / l (54.5 miles / gallon), which is a fair value of average corporate fuel consumption fuel economy; CAFE) in the US from 2025.

In particular, high performance and highly efficient engine technologies and transmissions have been developed to maximize fuel economy of vehicles, and this technology includes an increase in the number of gears, a new approach concept, a highly effective two-pump system, a fusion hybrid technology, automatic / manual fusion gear technologies and a hybrid transmission and the like.

An alloy steel used in transmission technology is used in carriers, gears, shafts, synchronous hubs, and the like of the transmission. A use ratio of the alloy steel is currently about 58 to 62% by weight based on the total weight of the transmission. In particular, the gears of the transmission and the like require the development of reduced size, high strength, and high-durability (reduced weight) materials.

In general, the gears of a vehicle transmission represent parts that perform a role of directly transmitting engine power to a differential system and effectively transmitting rotation or power between two or more shafts so that engine power is transmitted to a driving state of the vehicle. Since bending load and contact stress are simultaneously absorbed, high physical properties such as hardness, strength, ruggedness, fatigue strength and fatigue strength are required.

As an alternative to the above requirement, currently carburized steel such as SCM820PRH comprising 0.17 to 0.23% by weight of carbon (C), 0.5 to 0.7% by weight of silicon (Si), 0, 45 to 0.75% by weight of manganese (Mn), 1.95 to 2.25% by weight of chromium (Cr), 0.015 to 0.035% by weight of molybdenum (Mo), 0.0015% by weight of oxygen (O ₂ ) and the like are used.

However, in the carburized steel, fatigue failure such as breakage of the gear teeth occurs simply due to lack of bending strength and the like, and fatigue damage such as pitting easily occurs due to lack of fatigue strength and the like.

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

Summary

The present disclosure is made in an effort to provide a carburized alloy steel comprising carbon (C), silicon (Si), manganese (Mn), chromium (Cr), molybdenum (Mo), niobium (Nb), vanadium (V), titanium (Ti). , Nitrogen (N), boron (B), and the like, to improve physical properties such as hardness, strength, and ruggedness, and thus have improved durability, and to provide a method for producing the same.

An exemplary embodiment of the present invention provides a carburized alloy steel comprising: based on a total weight of the alloy steel, 0.1 to 0.35 wt% of carbon (C), 0.1 to 2 wt% of silicon (Si), 0.1 to 1.5% by weight of manganese (Mn), 3 to 5.5% by weight of chromium (Cr), 0.2 to 0.5% by weight of molybdenum (Mo), more than 0% by weight -% and 0.07% by weight or less of niobium (Nb), more than 0% by weight and 0.3% or less by weight of vanadium (V), more than 0% by weight and 0.2% by weight % or less of titanium (Ti), more than 0% by weight and 0.015% by weight or less of nitrogen (N), 0.02 to 0.005% by weight of boron (B) and an balance of iron (Fe) .: balance of iron).

In certain embodiments, a content of carbon (C) may be 0.18 to 0.33% by weight, a content of silicon (Si) may be 0.69 to 1.06% by weight, and a content of manganese (Mn) may be 0.74 to 0.98% by weight, a content of chromium (Cr) 3.2 to 5.3% by weight, a content of molybdenum (Mo) 0.29 to 0.38% by weight, a content of niobium (Nb ) 0.062 to 0.064% by weight, a content of vanadium (V) 0.19 to 0.27% by weight, a content of titanium (Ti) 0.14 to 0.18% by weight, a content of nitrogen (N ) 0.0051 to 0.0056% by weight and a content of boron (B) 0.0026 to 0.0043% by weight.

In certain embodiments, a content of carbon (C) may be 0.18% by weight, a content of silicon (Si) may be 1.06% by weight, a proportion of manganese (Mn) may be 0.98% by weight, a proportion of chromium (Cr) 5.3% by weight, a content of molybdenum (Mo) 0.38% by weight, a content of niobium (Nb) 0.064% by weight, a content of vanadium (V) 0.27% by weight, a content of titanium (Ti) is 0.14% by weight, a content of nitrogen (N) is 0.0051% by weight, and a content of boron (B) is 0.0026% by weight.

In certain embodiments, a transmission component of a vehicle may include a carburized alloy steel according to the present disclosure.

According to another exemplary embodiment of the present invention, there is provided a method of producing a carburized alloy steel, comprising: a first step of producing the alloy beam comprising, based on a total weight of the alloy steel, 0.1 to 0.35 wt% of carbon (C), 0.1 to 2% by weight of silicon (Si), 0.1 to 1.5% by weight of manganese (Mn), 3 to 5.5% by weight of chromium (Cr), 0.2 to 0.5% by weight of molybdenum (Mo), more than 0% by weight, and 0.07% by weight or less of niobium (Nb), more than 0% by weight, and 0.3% by weight or less Vanadium (V), more than 0% by weight and 0.2% or less by weight of titanium (Ti), more than 0% by weight and 0.015% or less by weight of nitrogen (N), 0.002 to 0.005% by weight % of boron (B) and an iron (Fe) and the like. A second step involves carburizing by heat treating the alloy steel at about 880 to 940 ° C for about 1.5 to 2 hours. In a third step, the carburized alloy steel is quenched with oil at about 80 to 120 ° C. In a fourth step, the oil-tarnished alloy steel is tempered at about 170 to 200 ° C for about one to three hours.

Here, in some embodiments, a content of carbon (C) may be 0.18 to 0.33% by weight, a content of silicon (Si) 0.69 to 1.06% by weight, a proportion of manganese (Mn) 0.74 to 0.98% by weight, a content of chromium (Cr) 3.2 to 5.3% by weight, a content of molybdenum (Mo) 0.29 to 0.38% by weight, a content of Niobium (Nb) 0.062 to 0.064% by weight, a content of vanadium (V) 0.19 to 0.27% by weight, a content of titanium (Ti) 0.14 to 0.18% by weight, a content of Nitrogen (N) 0.0051 to 0.0056% by weight and a content of boron (B) 0.0026 to 0.0043% by weight.

In certain embodiments, a content of carbon (C) may be 0.18% by weight, a content of silicon (Si) may be 1.06% by weight, a proportion of manganese (Mn) may be 0.98% by weight, a proportion of chromium (Cr) 5.3% by weight, a content of molybdenum (Mo) 0.38% by weight, a content of niobium (Nb) 0.064% by weight, a content of vanadium (V) 0.27% by weight, a content of titanium (Ti) is 0.14% by weight, a content of nitrogen (N) is 0.0051% by weight, and a content of boron (B) is 0.0026% by weight.

In some embodiments of the present invention having the above composition, it is possible to improve the durability, such as hardness, strength, ruggedness, fatigue strength and durability of a carburized alloy steel, and to facilitate solidification of the carburized alloy steel and thus ensure a degree of freedom in designing a vehicle and reduce manufacturing costs by a thickness reduction, a weight reduction of 20% and the like.

Detailed description

Terms or words used in the present disclosure and claims are not to be construed as limiting to typical or dictionary meanings, but should be construed broadly in order to accompany the technical idea of the present invention, based on the principle that The inventor may determine the concept of terms to describe his / her invention in the best way.

In the following, certain embodiments of the invention will be described in detail. The present disclosure relates to a carburized alloy steel having improved durability and a process for producing the same. In one aspect, the present invention relates to a carburized alloy steel having improved durability.

The carburized alloy steel having improved durability according to certain embodiments of the present invention comprises, based on a total weight of the alloy steel, 0.1 to 0.35 wt% of carbon (C), 0.1 to 2.0 wt% of silicon ( Si), 0.1 to 1.5% by weight of manganese (Mn), 3 to 5.5% by weight of chromium (Cr), 0.2 to 0.5% by weight of molybdenum (Mo), more as 0% by weight and 0.07% by weight or less of niobium (Nb), more than 0% by weight and 0.3% by weight or less of vanadium (V), more than 0% by weight and 0, 2% by weight or less of titanium (Ti), more than 0% by weight and 0.015% by weight or less of nitrogen (N), 0.002 to 0.005% by weight of boron (B) and an amount of iron (Fe), an unavoidable impurity and the like.

In certain embodiments, a content of carbon (C) may be 0.18% by weight, a content of silicon (Si) may be 1.06% by weight, a proportion of manganese (Mn) may be 0.98% by weight, a proportion of chromium (Cr) 5.3% by weight, a content of molybdenum (Mo) 0.38% by weight, a content of niobium (Nb) 0.064% by weight, a content of vanadium (V) 0.27% by weight, a content of titanium (Ti) is 0.14% by weight, a content of nitrogen (N) is 0.0051% by weight, and a content of boron (B) is 0.0026% by weight.

In certain embodiments, the impurities may include aluminum (Al), oxygen (O), phosphorus (P), sulfur (S), and the like. In certain embodiments, a content (also called content) of aluminum (Al) may be 0.006% by weight, an amount of oxygen (O) may be 0.0004% by weight, a proportion of phosphorus (P ) 0.011% by weight and a content of sulfur (S) 0.005% by weight.

More specifically, the reason why a numerical value of a ingredient restricting the heat-resistant cast steel according to certain embodiments of the present invention is substantiated is as follows.

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

Carbon (C) is the strongest intermediate matrix reinforcing element among the chemical components, and is combined with an element such as chromium (Cr) to form a carbide and thus improve the strength, hardness, and the like, and a role of increasing surface hardness during carburizing.

For the above role, it is preferable that the content of carbon (C) is about 0.1 to 0.35% by weight based on the total weight of the alloy steel. Here, when the ratio of carbon (C) is less than 0.1% by weight, the strength of the alloy steel may be reduced, and it may be difficult to secure the hardness by carburizing. On the other hand, when the ratio of carbon (C) is more than 0.35% by weight, the core hardness of the alloy steel increases due to excessive carburization to reduce the total hardness of the alloy beam.

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

Silicon (Si) takes a role of suppressing the formation of a pinhole of the alloy steel as a deoxidizer, whereby the strength of the alloy steel increases by a solid solution solidification effect by dissolving in a matrix and decreasing the activity of carbons (C) and such increases. For the aforementioned role, it is preferable that the content of silicon (Si) is about 0.1 to 2% by weight based on the total weight of the alloy. Here, when the ratio of silicon (Si) is less than about 0.1% by weight, the effect of deoxidizing hardly occurs, and on the other hand, in the case where the content of silicon (Si) is more than about 2 % By weight, the solid solution solidification effect of the matrix is excessively increased to reduce manufacturability, carburizing property, and the like.

(3) 0.1 to 1.5% by weight of manganese (Mn)

Manganese (Mn) takes a role of improving a quenching property of the alloy steel and improves the strength of the alloy steel and the like. For the above role, it is preferable that the content of manganese (Mn) is about 0.1 to 1.5% by weight. In the case where the content of manganese (Mn) is less than about 0.1% by weight, a sufficient quenching property and the like can not be ensured, and on the other hand, in the case where the content of manganese ( Mn) is more than about 1.5% by weight, grain boundary oxidation may occur and the mechanical properties of the alloy steel may deteriorate.

(4) 3 to 5.5% by weight of chromium (Cr)

Chromium (Cr) takes a role of improving a quenching property of the alloy steel, simultaneously ensuring hardenability and reduction of a tissue of the alloy steel, and promotes carburization and reduces carburization time by reacting with carbon (C) to form a fine carbide. For the aforementioned role, therefore, it is preferable that the content of chromium (Cr) is about 3 to 5.5% by weight. Here, when the content of chromium (Cr) is less than about 3% by weight, an effect of carbide formation is reduced, and on the other hand, when the proportion of chromium (Cr) is more than about 5.5% by weight, The strength of the alloy steel decreases, grain boundary oxidation occurs, and the effect of increasing the proportion is insignificant to cause an increase in manufacturing cost.

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

Molybdenum (Mo) takes a role of improving the hardenability, strength and the like of the alloy steel after quenching with oil or tempering, and ensures resistance to embrittlement. For the aforementioned role, it is preferable that the content of molybdenum (Mo) is about 0.2 to 0.5% by weight. Here, when the proportion of molybdenum (Mo) is less than about 0.2% by weight, the hardenability and strength of the alloy steel and the like can not be sufficiently ensured, and on the other hand, if the proportion of molybdenum (Mo) is more than 0.5 wt%, the processability and manufacturability of the alloy steel and the like may be reduced.

(6) More than 0% by weight and 0.07% by weight or less of niobium (Nb)

Niobium (Nb) is combined with nitrogen to form a nitride and the like to perform a role of miniaturizing the crystal grains, increases a recrystallization temperature and facilitates high-temperature carburization, and thus improves the hardenability and strength of the alloy steel and the like. For the aforementioned role is it is preferable that the content of niobium (Nb) is more than 0% by weight and about 0.07% by weight or less. Hereinafter, when the content of niobium (Nb) is 0.07% by weight, an effect of niobium (Nb) may be saturated, the strength may be reduced, and processability and manufacturability and the like may be reduced.

(7) More than 0% by weight and 0.3% by weight or less of vanadium (V)

Vanadium (V) takes a role of forming precipitates such as carbides, solidifying a matrix fabric by a precipitation strengthening effect, improving strength and wear resistance, and reducing crystal grains. For the aforementioned role, it is preferable that the proportion of vanadium (V) is more than 0% by weight and about 0.3% by weight or less. Here, when the content of vanadium (V) is more than about 0.3% by weight, the strength and hardness of the alloy steel and the like can be further reduced.

(8) more than 0% by weight and 0.2% by weight or less of titanium (Ti)

Titanium (Ti) plays a role of forming carbonitride to suppress the growth of crystal grains and to improve high temperature stability, strength, ruggedness and the like. For the above role, it is preferable that the proportion of titanium (Ti) is more than 0% by weight and about 0.2% by weight or less. Here, when the content of titanium (Ti) is more than 0.2% by weight, coarse precipitation may form and manufacturing costs may increase due to a reduction in a low-temperature impact property and saturation of the effect.

(9) more than 0% by weight and 0.015% by weight or less of nitrogen (N)

Nitrogen (N) plays a role of reducing austenite crystal grains and improves the tensile strength, yield strength and elongation of the alloy steel and the like. For the above role, it is preferable that the content of nitrogen (N) is more than 0% by weight and about 0.015% by weight or less. Here, when the content of nitrogen (N) is about 0.015% by weight or less, brittleness may be caused and durability and the like may be reduced.

(10) 0.002 to 0.005% by weight of boron (B)

Boron (B) takes a role of improving the hardenability of the alloy steel and the like, and hitherto, it is preferable that the content of boron (B) is about 0.002 to 0.005 wt%. Here, when the content of boron (B) is less than 0.002% by weight, it may be difficult to ensure sufficient hardenability of the alloy steel and, on the other hand, when the content of boron (B) is more than about 0.005% by weight For example, the strength and elongation of the alloy steel and the like may be reduced to reduce shock resistance and the like.

Since the carburized alloy steel having the aforementioned composition according to certain embodiments of the invention has improved hardness, strength, ruggedness, fatigue strength, and durability, it is advantageous that the carburized alloy steel is used in vehicle parts and the like. It is particularly advantageous that the carburized alloy steel is used in automatic transmissions or manual transmissions (manual transmissions) and the like, and among the transmissions it is particularly advantageous that the carburized alloy steel is used in carriers, fixed sprockets, gears, shafts, synchronous hubs or the like.

Hereinafter, further embodiments according to another aspect of the present invention relate to a method for producing a carburized alloy steel having improved durability.

The carburized alloy steel having improved durability according to the present invention may be suitably manufactured by a person skilled in the art in terms of a publicly known technology. To be more specific, the method for producing the carburized alloy steel having improved durability according to certain embodiments of the present invention comprises a first step of producing an alloy steel for carburizing comprising, based on the total weight of the alloy steel, 0.1 to 0.35 wt% Carbon (C), 0.1 to 2% by weight of silicon (Si), 0.1 to 1.5% by weight of manganese (Mn), 3 to 5.5% by weight of chromium (Cr), 0 , 2 to 0.5% by weight of molybdenum (Mo), more than 0% by weight and 0.07% by weight or less of niobium (Nb), more than 0% by weight and 0.3% by weight or less of vanadium (V), more than 0% by weight and 0.2% by weight or less of titanium (Ti), more than 0% by weight and 0.015% by weight or less of nitrogen (N), 0.002 to 0.005 % By weight of boron (B) and a balance (balance) of iron (Fe), unavoidable impurity and the like. In a second step, the alloy steel undergoes a carburizing heat treatment at about 880 to 940 ° C for about 1.5 to 2 hours. A third step involves oil quenching of the carburized, heat-retaining alloy steel at about 80 to 120 ° C. In a fourth step, the oil-quenched alloy steel is tempered at about 170 ° C to 200 ° C for about one to three hours.

In certain embodiments, in the second step, in the case where a heat treatment temperature is less than 880 ° C, since a heat treatment time increases, the productivity is below Reduced circumstances, and in the case where a heat treatment time is less than 1.5 hours, the times of providing, injecting and distributing carbons (C) are short, and hence carburization can not be performed sufficiently.

On the other hand, in the second step, in the case where the heat treatment temperature is more than about 940 ° C, the recrystallization of the alloy steel may occur to reduce mechanical properties and in the case where the heat treatment time is more than 2 hours Cover, there is an excessive carburization and a thermal deformation occur and increase the manufacturing cost.

In the third step, in the case where an oil quenching temperature is less than 80 ° C, or in the fourth step, in the case where the tempering temperature is less than about 170 ° C, the strength and the ruggedness may be difficult alloy steel due to the formation of retained austenite. In the case where the oil quenching temperature is more than 120 ° C or in the case where the tempering temperature is more than about 200 ° C, a fatigue property (durability) of the alloy steel and the like may increase due to an increase in residual austenite during a Rapid cooling process deteriorate and in the case where the tempering time is more than about 3 hours, it may be difficult to improve the durability and the like, due to a rapid reduction in the hardness of the alloy steel.

In the first step, in certain embodiments, a content of carbon (C) may be 0.18% by weight, a content of silicon (Si) may be 1.06% by weight, a proportion of manganese (Mn) may be 0.98% by weight, a content of chromium (Cr) 5.3% by weight, a content of molybdenum (Mo) 0.38% by weight, a content of niobium (Nb) 0.64% by weight, a content of vanadium (V) 0 , 27% by weight, a content of titanium (Ti) 0.14% by weight, a content of nitrogen (N) 0.0051% by weight, and a content of boron (B) 0.0026% by weight. In certain embodiments, an impurity may include aluminum (Al), oxygen (O), phosphorus (P), sulfur (S), and the like. In certain embodiments, the amount of aluminum (Al) may be 0.006% by weight, oxygen (O) 0.0004% by weight, phosphorus (P) 0.11% by weight, and sulfur (S ) 0.005% by weight.

[Examples]

Hereinafter, embodiments of the present invention will be described in detail by the examples. These examples are merely illustrative of certain embodiments of the present invention, and it will be apparent to those skilled in the art that the scope of the present invention should not be limited by these examples.

In order to compare the physical properties of the carburized alloy steel having improved durability according to the present disclosure, comparative examples and examples comprising the components as described in the following table were conducted according to conditions of carburizing temperature and time, quenching oil temperature, and tempering temperature and time , which are described in the following Table 2 applied. [Table 1] classification unit Comparative Example 1 Comparative Example 2 Comparative example 3 example 1 Example 2 C gw% 0.21 0.20 0.19 0.33 0.18 Si gw% 0.62 0.61 0.62 0.69 1.06 Mn gw% 0.64 0.60 0.57 0.74 0.98 Cr gw% 2.05 3.63 3.74 3.2 5.3 Not a word gw% 0.39 - 0.18 0.29 0.38 Nb gw% 0.028 0.028 0.027 0.062 0.064 V gw% - - - 0.19 0.27 Ti gw% - 0,002 - 0.18 0.14 B gw% - 0,012 - 0.0043 0.0026 N gw% 0.0078 0.0065 0.0082 0.0056 0.0051 al gw% 0.03 0,008 0,012 0,007 0,006 O gw% 0.0005 0.001 0.001 0.0005 0.0004 P gw% 0,012 0.01 0.01 0,012 0.011 S gw% 0.005 0,007 0,007 0.005 0.005

Table 1 is a table comparing the constituent components and proportions of Comparative Examples 1 to 3 according to the existing alloy steel and the constituent components and proportions of Examples 1 and 2 according to the present invention and impurities of aluminum (Al), oxygen (O), phosphorus (P), and sulfur (S) represent a very small proportion included in the comparative examples and the examples. [Table 2] classification Comparative Example 1 Comparative Example 2 Comparative example 3 example 1 Example 2 Carburizing temperature (° C) / hour (h) 930/2 940 / 1.67 930 / 1.83 880 / 1.5 940 / 1.83 Detering oil temperature (° C) 110 100 110 80 120 Tempering temperature (° C) / hour (h) 180/2 170/2 190 / 2.5 170 / 1.5 190/3

Table 2 is a table comparing, under the production conditions of Comparative Examples 1 to 3 and Examples 1 and 2 having the constituent components and the contents shown in Table 1, the carburizing temperatures and carburizing times, the quenching oil temperatures and the tempering temperatures and times. Here, all of Comparative Examples 1 to 3 and Examples 1 and 2 satisfy the carburizing temperature and time, the quenching oil temperature, and the tempering temperature and time according to the embodiments of the present invention. [Table 3] classification Comparative Example 1 Comparative Example 2 Comparative example 3 example 1 Example 2 Surface hardness (HV) 740 730 740 810 815 Core hardness (HV) 495 507 514 560 575 Tensile strength (kgf / cm ² ) 3 106 1207 1218 1202 1232 Yield strength (kgf / cm ² ) 957 3 107 1091 1082 1108 Carburizing depth (mm) 0.71 0. 71 0.73 0.76 0.78 Impact value (J) 27.8 24.6 39.8 46.4 47.2 Rotational bending strength (K) 105 11.5 125 142 144 Contact fatigue life (number, cycle) 4,150,000 8,370,000 9,020,000 11,200,000 12,400,000

Table 3 is a table in which Comparative Examples 1 to 3 and Examples 1 to 2 were prepared with the constituent components and contents shown in Table 1 under the conditions of Table 2, and the surface hardness, core hardness, tensile strength, yield strength, the carburizing depth, the impact values, the rotational bending strength and the contact fatigue are compared.

The surface hardness and core hardness were measured according to the KS B 0811 measuring method using the Micro-Vickers Hardness tester. In the case of rotational bending strength, L10 life was measured according to the KS B ISO 1143 Measuring method under the condition of the maximum bending moment of about 20 kgfm, a rotation speed of about 200 to 3000 rpm, a maximum load of about 100 kg or less, and a three phase electric power at 220 V and 7 kW using a common line diameter of about 4 mm measured by the rotational flexural fatigue tester. The L10 life is the fatigue life of the sample and means the total number of rotations of the Rotary Flexure Endurance Tester until approximately 10% of the sample is damaged. Further, in the case of contact fatigue, the rotational speed of the contact fatigue test roller was measured before cracks formed in the sample with the surface pressure boundary condition of about 332 kg / mm ^{2, the} lubricant temperature of about 80 ° C and the lubricant amount of about 1 , 2 l / min using the contact fatigue experimenting apparatus.

Examples 1 and 2 showed values of surface hardness and core hardness both unexpectedly larger than those of Comparative Examples 1 to 3, the values of tensile strength and yield strength were highest in Example 2, and the carburizing depth of Examples 1 and 2 was larger than that Comparative Examples 1 to 3 and the impact value, rotational flexural strength and contact fatigue life of Examples 1 and 2 were unexpectedly better in comparison with those of Comparative Examples 1 to 3.

Therefore, it could be confirmed that in Examples 1 and 2 according to the embodiments of the present invention, compared to Comparative Examples 1 to 3, the surface hardness was unexpectedly better at around 10%, the core hardness was unexpectedly better at around 12% The tensile strength and yield strength were unexpectedly better at about 5%, the carburizing depth was unexpectedly better at about 7%, the impact value was about 52% better, the rotational flexural strength was unexpectedly better at about 24%, and the contact fatigue life was unexpectedly better at about 72%. was.

In particular, it can be confirmed that Example 2 according to one embodiment of the present invention has physical properties which were significantly better compared with those of Example 1 and Comparative Examples 1 to 3, the constituent component and the content of Example 2 in comparison with Example 1 under certain conditions are preferable.

As described above, the present invention has been described in terms of specific embodiments of the present invention, however, these embodiments are for the purpose of illustration only, and the present invention is not limited thereto. Embodiments that have been described may be varied or modified by those skilled in the art without departing from the scope of the present invention, and various changes and modifications are within the technical spirit of the present invention and the equivalent scope of the claims described below, possible.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• KR 10-2014-175183 [0001]

Cited non-patent literature

• KS B ISO 1143 [0048]

Claims (7)

Carburized alloy steel, comprising: based on a total weight of the alloy steel 0.1 to 0.35% by weight of carbon (C), 0.1 to 2% by weight of silicon (Si), 0.1 to 1.5% by weight of manganese (Mn ), 3 to 5.5% by weight of chromium (Cr), 0.2 to 0.5% by weight of molybdenum (Mo), 0 to 0.07% by weight of niobium (Nb), 0 to 0, 3% by weight of vanadium (V), 0 to 0.2% by weight of titanium (Ti), 0 to 0.015% by weight of nitrogen (N), 0.002 to 0.005% by weight of boron (B) and a balance Iron (Fe). A carburized alloy steel according to claim 1, wherein a content of carbon (C) is 0.18 to 0.33, a content of silicon (Si) is 0.69 to 1.06 wt%, a proportion of manganese (Mn) 0.74 to 0.98% by weight, a content of chromium (Cr) is 3.2 to 5.3% by weight, a content of molybdenum (Mo) is 0.29 to 0.38% by weight, a proportion of niobium (Nb) is 0.062 to 0.064% by weight, a proportion of vanadium (V) is 0.19 to 0.27% by weight, a proportion of titanium (Ti) is 0.14 to 0.18% by weight %, a content of nitrogen (N) is 0.0051 to 0.0056% by weight, and a content of boron (B) is 0.0026 to 0.0043% by weight. A carburized alloy steel according to claim 1 or 2, wherein a content of carbon (C) is 0.18% by weight, a content of silicon (Si) is 1.06% by weight, a content of manganese (Mn) is 0.98 % By weight, a content of chromium (Cr) is 5.3% by weight, a content of molybdenum (Mo) is 0.38% by weight, a content of niobium (Nb) is 0.64% by weight, a proportion of vanadium (V) is 0.27% by weight, a proportion of titanium (Ti) is 0.14% by weight, a proportion of nitrogen (N) is 0.0051% by weight and a fraction of boron ( B) is 0.0026% by weight. Transmission component of a vehicle comprising the alloy steel according to one of claims 1 to 3. A method of making a carburized alloy steel, comprising: a first step of producing the alloy steel, wherein the alloy steel comprises: based on a total weight of the alloy steel, 0.1 to 0.35 wt% of carbon (C), 0.1 to 2 wt% of silicon (Si), 0.1 to 1.5% by weight of manganese (Mn), 3 to 5.5% by weight of chromium (Cr), 0.2 to 0.5% by weight of molybdenum (Mo), 0 to 0, 07% by weight of niobium (Nb), 0% to 0.3% by weight of vanadium (V), 0% to 0.2% by weight of titanium (Ti), 0% to 0.015% by weight of nitrogen (N), 0.002 to 0.005% by weight of boron (B) and a balance of iron (Fe), a second step of carburizing by heat-treating the alloy steel at 880 to 940 ° C for 1.5 to 2 hours; a third step of quenching with oil of the carburized alloy steel at 80 to 120 ° C; and a fourth step of tempering the oil-quenched alloy steel at 170 to 200 ° C for 1 to 3 hours. The method of claim 5, wherein the content of carbon (C) is 0.18 to 0.33, a content of silicon (Si) is 0.69 to 1.06% by weight, a content of manganese (Mn) is 0 Is 74 to 0.98% by weight, a content of chromium (Cr) is 3.2 to 5.3% by weight, a content of molybdenum (Mo) is 0.29 to 0.38% by weight Content of niobium (Nb) is 0.062 to 0.064% by weight, a content of vanadium (V) is 0.19 to 0.27% by weight, a content of titanium (Ti) is 0.14 to 0.18% by weight A content of nitrogen (N) is 0.0051 to 0.0056% by weight, and a content of boron (B) is 0.0026 to 0.0043% by weight. A method according to claim 5 or 6, wherein a content of carbon (C) is 0.18% by weight, a content of silicon (Si) is 1.06% by weight, a content of manganese (Mn) is 0.98% by weight -% is, a proportion of chromium (Cr) is 5.3% by weight, a content of molybdenum (Mo) is 0.38% by weight, a content of niobium (Nb) is 0.064% by weight, a proportion of Vanadium (V) is 0.27% by weight, a content of titanium (Ti) is 0.14% by weight, a content of nitrogen (N) is 0.0051% by weight, and a proportion of boron (B) 0.0026% by weight.