KR20120110541A - Shape steel and method of manufacturing the shape steel - Google Patents

Abstract

PURPOSE: Shaped steel and a manufacturing method thereof are provided to obtain shaped steel applicable to a track shoe by increasing the contents of manganese and chrome to improve the wear resistance. CONSTITUTION: A method for manufacturing shaped steel comprises the steps of: reheating slab to 1150-1250°C and cooling the rolled steel to 450-600°C, wherein the slab comprises carbon of 0.20-0.26 weight%, silicon of 0.15-0.30 weight%, manganese of 1.1-1.4 weight%, phosphorous of 0.030 weight% or less, sulfur of 0.030 weight% or less, chrome of 0.25-0.50 weight%, aluminum of 0.015-0.035 weight%, titanium of 0.010-0.030 weight%, boron of 5-30ppm, and iron and inevitable impurities of the remaining amount.

Description

SHAPE STEEL AND METHOD OF MANUFACTURING THEREOF {SHAPE STEEL AND METHOD OF MANUFACTURING THE SHAPE STEEL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for manufacturing a steel, and more particularly, to a steel having an excellent wear resistance by improving the core hardness characteristics by controlling alloy components and process conditions, and a method of manufacturing the same.

Recently, with the development of transportation equipment and heavy equipment field, the metal material sector is required to have high strength and excellent wear resistance. In particular, in the case of caterpillar that takes the load of heavy equipment such as fork crane, mechanical properties are considered very important by the environment.

One object of the present invention is to provide a method for producing a shaped steel having excellent wear resistance by improving the hardenability by controlling alloying components and process conditions.

Another object of the present invention is to provide a section steel having high strength and excellent wear resistance.

Shape steel manufacturing method according to an embodiment of the present invention for achieving the above object is carbon (C): 0.20 ~ 0.26% by weight, silicon (Si): 0.15 ~ 0.30% by weight, manganese (Mn): 1.1 ~ 1.4 weight %, Phosphorus (P): 0.030 wt% or less, sulfur (S): 0.030 wt% or less, chromium (Cr): 0.25-0.50 wt%, aluminum (Al): 0.015-0.035 wt%, titanium (Ti): 0.010 ~ 0.030% by weight, boron (B): reheating the cast steel consisting of 5 to 30ppm and the remaining iron (Fe) and other unavoidable impurities to 1150 ~ 1250 ℃; Rolling the reheated cast steel; And cooling the rolled steel to 450 to 600 ° C.

In addition, the cast may further include one or more of nickel (Ni): 0.2% by weight or less and copper (Cu): 0.3% by weight or less.

Shape steel according to an embodiment of the present invention for achieving the other object is carbon (C): 0.20 ~ 0.26% by weight, silicon (Si): 0.15 ~ 0.30% by weight, manganese (Mn): 1.1 ~ 1.4% by weight, phosphorus (P): 0.030 wt% or less, Sulfur (S): 0.030 wt% or less, Chromium (Cr): 0.25 ~ 0.50 wt%, Aluminum (Al): 0.015 ~ 0.035 wt%, Titanium (Ti): 0.010 ~ 0.030 wt% %, Boron (B): 5 to 30ppm and the remaining iron (Fe) and is characterized by consisting of other unavoidable impurities.

According to the present invention, the steel and the method of manufacturing the same may increase the content of chromium, which is an element that improves hardenability, and chromium, which is an element that improves hardenability.

Accordingly, the shaped steel according to the present invention can be utilized in track shoes, which are one of the tracked parts that occupy the load of heavy equipment such as fork cranes.

1 is a flow chart schematically showing a method for manufacturing a shaped steel according to an embodiment of the present invention.
2 is a graph showing the results of Jomini test according to Example 1 and Comparative Examples 1,2.
3 is a photograph showing a track shoe manufactured by a method of manufacturing a section steel according to an embodiment of the present invention.

Advantages and features of the present invention, and methods of achieving the same will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the art to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown.

Section steel

The steel according to the present invention is carbon (C): 0.20 to 0.26% by weight, silicon (Si): 0.15 to 0.30% by weight, manganese (Mn): 1.1 to 1.4% by weight, phosphorus (P): 0.030% by weight or less, sulfur (S): 0.030 wt% or less, Chromium (Cr): 0.25 ~ 0.50 wt%, Aluminum (Al): 0.015 ~ 0.035 wt%, Titanium (Ti): 0.010 ~ 0.030 wt%, Boron (B): 5 ~ 30 ppm And the remaining iron (Fe) and other unavoidable impurities.

In addition, the shaped steel according to the present invention may further include one or more of nickel (Ni): 0.2% by weight or less and copper (Cu): 0.3% by weight or less for the purpose of improving strength.

Hereinafter, the role and content of each component included in the section steel according to the present invention will be described.

Carbon (C)

In the present invention, carbon (C) is added to secure the strength of the steel.

The carbon (C) is preferably added in a content ratio of 0.20 to 0.26% by weight of the total weight of the steel according to the present invention.

If the content of carbon (C) is added less than 0.20% by weight, it may be difficult to secure the strength. On the contrary, when the content of carbon (C) exceeds 0.26% by weight, the strength of the steel is increased, but there is a problem that the core hardness and the weldability are lowered.

Silicon (Si)

In the present invention, silicon (Si) is added as a deoxidizer for removing oxygen in the steel in the steelmaking process. Silicon (Si) also has a solid solution strengthening effect.

The silicon (Si) is preferably added in a content ratio of 0.15 to 0.30% by weight of the total weight of the steel.

If the content of silicon (Si) is less than 0.15% by weight, the silicon addition effect may not be properly exhibited. On the contrary, when the content of silicon (Si) exceeds 0.30% by weight, an oxide is formed on the surface of the steel, thereby degrading weldability of the steel.

Manganese (Mn)

Manganese (Mn) is an element that increases the strength and toughness of the steel and increases the hardenability of the steel, and the addition of manganese (Mn) has less deterioration in ductility when increasing the strength than the addition of carbon (C). Manganese (Mn) also contributes to the hardenability of the steel.

The manganese (Mn) is preferably added at 1.1 to 1.4% by weight of the total weight of the steel according to the present invention. When the content of manganese (Mn) is less than 1.1% by weight, it may be difficult to secure strength even if the carbon (C) content is high. On the contrary, when the content of manganese (Mn) exceeds 1.4% by weight, the amount of MnS-based nonmetallic inclusions may increase, which may cause defects such as cracking during welding.

Phosphorus (P)

Phosphorus (P) contributes partly to strength improvement, but it is a representative element that lowers the secondary process embrittlement. Therefore, in the present invention, the content of phosphorus (P) was limited to 0.030% by weight or less of the total weight of the steel.

Sulfur (S)

Sulfur (S), like phosphorus (P), is an impurity element present in steel. The sulfur (S) corresponds to impurities that are precipitated in the form of MnS and the like to increase the amount of precipitates.

Therefore, in the present invention, the content of sulfur (S) was limited to 0.03% by weight or less of the total weight of the steel.

Nickel (Ni)

In the present invention, nickel (Ni) is refined to solidify the crystal grains and strengthen the matrix by austenite and ferrite, but when added in a large amount, it is uneconomical and may cause a problem of red brittleness.

Therefore, the nickel (Ni) is preferably added to 0.2% by weight or less of the total weight of the steel according to the present invention.

Copper (Cu)

In the present invention, copper (Cu) is an element effective for increasing strength and improving toughness. At this time, the copper (Cu) contributes to the solid solution strengthening effect of the steel through a constant content control together with silicon (Si) and manganese (Mn), there is a fear that the surface properties of the steel is lowered when excessively added.

Therefore, the copper (Cu) is preferably added in a content ratio of 0.3% by weight or less of the total weight of the steel according to the present invention.

Chrome (Cr)

In the present invention, chromium (Cr) is an effective element for improving hardenability by improving hardenability.

The chromium (Cr) is preferably added in 0.25 ~ 0.50% by weight of the total weight of the steel. If the content of chromium (Cr) is less than 0.25% by weight, the amount of the chromium (Cr) is insignificant and the addition effect cannot be properly exhibited. On the contrary, when the content of chromium (Cr) exceeds 0.50% by weight, there is a problem of deteriorating the weldability or the heat affected zone (HAZ) toughness.

Aluminum (Al)

Aluminum (Al) serves as a deoxidizer to remove oxygen in the steel.

The aluminum (Al) is preferably added in 0.015 ~ 0.035% by weight of the total weight of the steel. If the content of aluminum (Al) is added less than 0.015% by weight, the deoxidation effect is insufficient. On the contrary, when the content of aluminum (Al) exceeds 0.035% by weight, Al ₂ O ₃ is formed to deteriorate toughness.

Titanium (Ti)

In the present invention, titanium (Ti) forms TiN upon reheating, thereby inhibiting austenite grain growth, thereby miniaturizing the structure of the steel.

The titanium (Ti) is preferably added in 0.01 to 0.03% by weight of the total weight of the steel. If the content of titanium (Ti) is less than 0.01% by weight, the titanium addition effect may not be properly exhibited. On the contrary, when the content of titanium (Ti) exceeds 0.03% by weight, TiN precipitates are coarsened and the effect of suppressing grain growth is reduced.

Boron (B)

Boron (B) is a strong hardenable element that contributes to the strength improvement of steel.

In the present invention, boron (B) is preferably added in 5 ~ 30ppm of the total weight of the steel.

If the content of boron (B) is less than 5ppm, the strength improvement effect may not be properly exhibited. On the contrary, when the content of boron (B) exceeds 30ppm of the total weight of the steel, there is a problem of material deviation due to grain boundary segregation.

Manufacturing method of steel section

1 is a flow chart schematically showing a method for manufacturing a shaped steel according to an embodiment of the present invention.

Referring to FIG. 1, the illustrated shaped steel manufacturing method includes a reheating step S110, a forming step S120, and a cooling step S130.

Reheat

In the reheating step (S110), carbon (C): 0.20 to 0.26 wt%, silicon (Si): 0.15 to 0.30 wt%, manganese (Mn): 1.1 to 1.4 wt%, phosphorus (P): 0.030 wt% or less, sulfur (S): 0.030 wt% or less, Chromium (Cr): 0.25 ~ 0.50 wt%, Aluminum (Al): 0.015 ~ 0.035 wt%, Titanium (Ti): 0.010 ~ 0.030 wt%, Boron (B): 5 ~ 30 ppm And reheat the cast steel consisting of the remaining iron (Fe) and other unavoidable impurities.

The cast may further include nickel (Ni): 0.2 wt% or less and copper (Cu): 0.3 wt% or less for the purpose of securing strength.

At this time, the reheating temperature is preferably carried out at 1150 ~ 1250 ℃. If the reheating temperature is less than 1150 ° C., there is a problem that the reheating temperature is low to increase the rolling load. On the contrary, when the reheating temperature exceeds 1250 ° C, there is a problem in that it is difficult to secure the strength of the steel produced by coarsening austenite grains.

Rolling

In the rolling step S120, the reheated cast steel is rolled by the reheating step S110. At this time, the reheated cast steel in the rolling step (S120) may be rolled into a specific shape by applying an appropriate pressure. In particular, the cast steel may be rolled in the form of a track shoe.

At this time, it is preferable to perform finish rolling temperature at 700-950 degreeC.

If the finish rolling temperature is less than 700 ° C, abnormal reverse rolling may occur to reduce ductility. On the contrary, when the finish rolling temperature exceeds 950 ° C, there is a problem in that the strength of the steel to be produced is sharply lowered.

Cooling

In the cooling step (S130) to cool the rolled steel to the cooling end temperature. Cooling can be effected by means of an air blowing method that directly injects air against the surface of the rolled steel.

In the cooling step (S130) it is preferable to perform the cooling end temperature is 450 ~ 600 ℃.

If the cooling end temperature is less than 450 ℃ it can increase the yield strength due to the generation of fine grains. On the contrary, when the cooling end temperature exceeds 600 ℃, due to the formation of FeTiP precipitates there is a fear that the content of effective titanium (Ti) to precipitate the solid solution carbon is reduced and the moldability is lowered.

After the cooling step S130, air cooling may proceed to room temperature.

The steel produced through the manufacturing process (S110 ~ S130) is to increase the content of chromium, which is an element to improve the hardenability and manganese to increase the hardenability, thereby improving the wear resistance by increasing the hardenability characteristic of the core hardness Can be.

In this case, the section steel manufactured through the manufacturing process may be utilized as a track shoe that is one of the tracked parts that occupy the load of heavy equipment such as a fork crane.

Example

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

Details that are not described herein will be omitted since those skilled in the art can sufficiently infer technically.

1. Specimen Manufacturing

Specimens according to Example 1 and Comparative Examples 1 and 2 were prepared under the compositions shown in Tables 1 and 2 and the process conditions described in Table 3.

[Table 1] (unit:% by weight)

[Table 2] (unit:% by weight)

[Table 3]

2. Evaluation of mechanical properties

Table 4 shows the results of evaluation of the mechanical properties of the specimen prepared according to Example 1 and Comparative Examples 1 and 2, Figure 2 is a graph showing the Zoni mini test results.

[Table 4]

Referring to Tables 1 to 4, in the case of Example 1, it can be seen that the point-specific zomni hardness (HRC) corresponding to 1.5 mm, 11 mm, and 15 mm from the surface of the specimen indicates 47.3, 44.5, and 38.7, respectively. have.

In the case of Example 1, as shown in Figure 2, it can be confirmed that the deviation of the roughness of the roughness (HRC) for each distance has a small slope has a gentle curve.

On the other hand, the process conditions are similar to Example 1, but in the case of Comparative Example 1 in which the contents of manganese (Mn), chromium (Cr) and titanium (Ti) are outside the component range of the present invention, 1.5 mm from the surface of the specimen to the center direction. It can be seen that the point-wise roughness (HRC) corresponding to 11 mm and 15 mm represents 46.7, 26.7, and 20.5, respectively.

In the case of the Comparative Example 1, as shown in Figure 2, it can be seen that the deviation of the roughness (HRC) for each distance is severe compared to Example 1, the slope is very steep.

On the other hand, the process conditions are the same as in Example 1, but in the case of Comparative Example 2, the content of carbon (C), chromium (Cr), aluminum (Al) and titanium (Ti) is outside the component range of the present invention It can be seen that the point-specific roughness hardness (HRC) corresponding to 1.5 mm, 11 mm, and 15 mm from the surface represents 54.5, 50.5, and 41.0, respectively.

In the case of Comparative Example 2, as shown in Figure 2, it can be seen that the deviation of the roughness (HRC) for each distance is severe compared to Example 1, the steep slope.

That is, as in Comparative Example 2, when the carbon (C) is added excessively, the surface strength can be increased, but when the chromium (C) content is less than the component range of the present invention, the hardness of the core is sharply lowered and hardenability You can see this falling.

As can be seen from the above experimental results, in the case of Example 1 it can be seen that the smallest deviation between the surface and the center of the Jomini hardness, which improves the hardenability of manganese, an element that increases the hardenability This is due to the increase in the amount of chromium added, which means that the wear resistance is excellent due to the increase in the hardenability, which is the core hardness property.

3 is a photograph showing a track shoe manufactured by a method of manufacturing a section steel according to an embodiment of the present invention.

Referring to FIG. 3, a section steel manufactured by a section steel manufacturing method according to an exemplary embodiment of the present invention may be utilized as a track shoe that is one of a crawler component that occupies a load of heavy equipment such as a fork lane.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. Such changes and modifications are intended to fall within the scope of the present invention unless they depart from the scope of the present invention. Accordingly, the scope of the present invention should be determined by the following claims.

S110: Reheating step
S120: Rolling Step
S130: cooling stage

Claims (7)

Carbon (C): 0.20 to 0.26 wt%, Silicon (Si): 0.15 to 0.30 wt%, Manganese (Mn): 1.1 to 1.4 wt%, Phosphorus (P): 0.030 wt% or less, Sulfur (S): 0.030 wt % Or less, Chromium (Cr): 0.25 to 0.50 wt%, Aluminum (Al): 0.015 to 0.035 wt%, Titanium (Ti): 0.010 to 0.030 wt%, Boron (B): 5 to 30 ppm and the remaining iron (Fe) Reheating the cast steel made of and other unavoidable impurities to 1150 to 1250 ° C .;
Rolling the reheated cast steel; And
Cooling the rolled steel to 450 ~ 600 ℃; manufacturing method of the shaped steel comprising a.
The method of claim 1,
On the cast steel
Nickel (Ni): 0.2% by weight or less and copper (Cu): 0.3% by weight or less of the manufacturing method characterized in that it further comprises.
The method of claim 1,
In the rolling step,
Finishing rolling temperature is 700 ~ 950 ℃ manufacturing method of the shaped steel, characterized in that carried out.
The method of claim 1,
The cooling is
A method for producing a shaped steel, which is carried out by an air blowing method.
The method of claim 1,
In the rolling step,
And the cast steel is rolled in the form of a track shoe.
Carbon (C): 0.20 to 0.26 wt%, Silicon (Si): 0.15 to 0.30 wt%, Manganese (Mn): 1.1 to 1.4 wt%, Phosphorus (P): 0.030 wt% or less, Sulfur (S): 0.030 wt % Or less, Chromium (Cr): 0.25 to 0.50 wt%, Aluminum (Al): 0.015 to 0.035 wt%, Titanium (Ti): 0.010 to 0.030 wt%, Boron (B): 5 to 30 ppm and the remaining iron (Fe) And steel, characterized in that consisting of and other unavoidable impurities.
The method according to claim 6,
The section steel
Nickel (Ni): 0.2% by weight or less and copper (Cu): 0.3% by weight or less of the shaped steel, characterized in that it further comprises.

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