KR20130034204A - Steel and method for manufacturing the same - Google Patents
Steel and method for manufacturing the same Download PDFInfo
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- KR20130034204A KR20130034204A KR1020110098101A KR20110098101A KR20130034204A KR 20130034204 A KR20130034204 A KR 20130034204A KR 1020110098101 A KR1020110098101 A KR 1020110098101A KR 20110098101 A KR20110098101 A KR 20110098101A KR 20130034204 A KR20130034204 A KR 20130034204A
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
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Abstract
Description
The present invention relates to a steel manufacturing technique, and more specifically, it is possible to predict the impact value according to the alloy component of the track shoe (Track Shoe) steel, and also to predict the alloy composition having a target impact value in the production of track shoe steel It relates to a steel and a method for producing the same.
In addition to the recent performance improvements in the field of transport equipment and heavy equipment, excellent mechanical properties are required in the material sector of these fields. Especially for the caterpillar, which takes the load of heavy equipment such as fork crane, mechanical properties are very important according to the use environment. In particular, the track shoe (Track Shoe) is a component of the caterpillar is required to have excellent impact properties, which can be secured from the material properties of the steel material.
In general, factors affecting the impact properties of steel materials are alloy composition and process conditions. In the track shoe steel, it may be easier to manufacture the steel if the impact properties can be predicted according to the alloy composition and other influence factors under the same process conditions.
In connection with the present invention, Korean Patent Publication No. 10-2006-0071099 (published on June 26, 2006) discloses a method for predicting yield strength and yield ratio after assembling of an electric resistance welding line pipe.
An object of the present invention is to provide a steel for track shoes that can easily predict the impact value of the steel for track shoes according to the alloy component.
Another object of the present invention is to provide a steel production method capable of predicting an alloy composition having a target impact value in manufacturing steel for track shoes.
Steel according to an embodiment of the present invention for achieving the above one object is carbon (C): 0.24 ~ 0.26% by weight, silicon (Si): 0.17 ~ 0.26% by weight, manganese (Mn): 0.95 ~ 1.1% by weight, Phosphorus (P): 0.018 wt% or less, Sulfur (S): 0.01 wt% or less, Chromium (Cr): 0.14 ~ 0.16 wt%, Nickel (Ni): 0.05 ~ 0.07 wt%, Molybdenum (Mo): 0.01 ~ 0.03 Weight%, aluminum (Al): 0.03 to 0.05 weight%, copper (Cu): 0.1 to 0.2 weight%, titanium (Ti): 0.02 to 0.05 weight%, boron (B): 10 to 30 ppm, nitrogen (N): 100 ppm or less, oxygen (O): 40 ppm or less and the remaining iron (Fe) and other inevitable impurities, characterized in that having a 25 ℃ impact value according to the following equation (1).
[Equation 1]
25 ℃ Impact Value (Kgfm / cm 2 ) = -51.21 x (7.023 x [S] -0.003) + 9.66
(In Equation 1, [S] is the weight% of sulfur in the composition.)
Steel according to another embodiment of the present invention for achieving the above object is carbon (C): 0.24 ~ 0.26% by weight, silicon (Si): 0.17 ~ 0.26% by weight, manganese (Mn): 0.95 ~ 1.1% by weight , Phosphorus (P): 0.018 wt% or less, sulfur (S): 0.01 wt% or less, chromium (Cr): 0.14 to 0.16 wt%, nickel (Ni): 0.05 to 0.07 wt%, molybdenum (Mo): 0.01 to 0.03% by weight, aluminum (Al): 0.03-0.05% by weight, copper (Cu): 0.1-0.2% by weight, titanium (Ti): 0.02-0.05% by weight, boron (B): 10-30 ppm, nitrogen (N) : 100ppm or less, oxygen (O): 40ppm or less and the remaining iron (Fe) and other inevitable impurities, characterized in that having a 25 ℃ impact value according to the following equation (2).
&Quot; (2) "
25 ℃ Impact value (Kgfm / cm 2 ) = -51.21 x [sulfide] + 9.66
(Sulfide in Equation 2 is the weight percentage of sulfide formed in steel)
At this time, the steel
A sulfide according to Equation 3 below may be formed.
&Quot; (3) "
[sulfide] = 7.023 x [S] -0.003
(Sulfide in Equation 3 is the weight% of sulfide formed in the steel, [S] is the weight% of the sulfur in the composition)
Steel manufacturing method according to another embodiment of the present invention for achieving the above another object is carbon (C): 0.24 ~ 0.26% by weight, silicon (Si): 0.17 ~ 0.26% by weight, manganese (Mn): 0.95 ~ 1.1 weight %, Phosphorus (P): 0.018 wt% or less, sulfur (S): 0.01 wt% or less, chromium (Cr): 0.14 to 0.16 wt%, nickel (Ni): 0.05 to 0.07 wt%, molybdenum (Mo): 0.01 ~ 0.03% by weight, aluminum (Al): 0.03-0.05% by weight, copper (Cu): 0.1-0.2% by weight, titanium (Ti): 0.02-0.05% by weight, boron (B): 10-30 ppm, nitrogen (N ): Preparing a slab composed of 100 ppm or less, oxygen (O): 40 ppm or less and remaining iron (Fe) and other unavoidable impurities; And after reheating the cast steel at 1150 to 1250 ° C., hot rolling to a finish rolling temperature of 700 to 950 ° C., and then cooling the steel to 450 ° C. to 600 ° C .; It is characterized by determining the content of sulfur (S) from the impact value.
[Equation 1]
25 ℃ Impact Value (Kgfm / cm 2 ) = -51.21 x (7.023 x [S] -0.003) + 9.66
Where [S] is the weight percent of sulfur in the composition
Steel according to the present invention and its manufacturing method can predict the impact value of the track shoe (Track Shoe) steel according to the alloy composition through the above equations (1) and (2), and also aimed at the production of steel for track shoes The alloy composition which has an impact value can be predicted.
1 schematically shows a method for manufacturing steel for track shoes according to an embodiment of the present invention.
Figure 2 shows the 25 ℃ impact value according to the content of sulfide (sulfide) for the track shoe steel specimens according to the present invention.
Figure 3 for the track shoe steel specimens according to the invention, shows the content of sulfide according to the content of sulfur.
Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.
Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the track shoe steel according to a preferred embodiment of the present invention and a manufacturing method thereof.
Track shoe steel according to the present invention is carbon (C): 0.24 ~ 0.26% by weight, silicon (Si): 0.17 ~ 0.26% by weight, manganese (Mn): 0.95 ~ 1.1% by weight, phosphorus (P): 0.018% by weight or less , Sulfur (S): 0.01% by weight or less, chromium (Cr): 0.14 to 0.16% by weight, nickel (Ni): 0.05 to 0.07% by weight, molybdenum (Mo): 0.01 to 0.03% by weight, aluminum (Al): 0.03 ~ 0.05 wt%, Copper (Cu): 0.1 ~ 0.2 wt%, Titanium (Ti): 0.02 ~ 0.05 wt%, Boron (B): 10 ~ 30ppm, Nitrogen (N): 100ppm or less, Oxygen (O): 40ppm And the remaining iron (Fe) and other inevitable impurities.
Hereinafter, the role and content of each component will be described.
Carbon (C)
Carbon (C) is added to secure the strength of the steel.
The carbon is preferably added in 0.24 to 0.26% by weight of the total weight of the steel. If the added amount of carbon (C) is less than 0.24% 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 impact value and the weldability are lowered.
Silicon (Si)
Silicon (Si) acts as a deoxidizer and contributes to strength enhancement through solid solution strengthening.
The silicon is preferably added in a content ratio of 0.17 to 0.26% by weight of the total weight of the steel. When the content of silicon (Si) is less than 0.17% by weight, the silicon addition effect may not be properly exhibited. On the contrary, when the content of silicon (Si) exceeds 0.26% by weight, an oxide is formed on the surface of the steel, thereby lowering 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 is preferably added at 0.95 to 1.1% by weight of the total weight of the steel. When the added amount of manganese (Mn) is less than 0.95% by weight, it is difficult to secure sufficient strength. On the contrary, when the amount of manganese exceeds 1.1% by weight, the amount of MnS-based nonmetallic inclusions increases, 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 0.018% 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) is an inclusion forming element, and forms a sulfide (Sulfide) in the form of MnS. Such sulfides impair the impact properties of steel for track shoes. Therefore, in the present invention, the content of sulfur (S) is limited to 0.01% by weight or less based on the total weight of the steel material.
Chrome (Cr)
Chromium (Cr) is an effective element for improving hardenability by improving hardenability.
The chromium is preferably added in 0.14 to 0.16% by weight of the total weight of the steel. If the content of chromium (Cr) is less than 0.14% 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 0.22% by weight, there is a problem of deteriorating the weldability or the heat affected zone (HAZ) toughness.
Nickel (Ni)
Nickel (Ni) fine grains and solidify in the austenite and ferrite to strengthen the matrix.
The nickel is preferably added at 0.05 to 0.07% by weight of the total weight of the steel. When the amount of nickel added is less than 0.05% by weight, the effect of addition is insufficient. On the contrary, when the addition amount of nickel exceeds 0.07 weight%, there exists a possibility of causing red brittleness.
Molybdenum (Mo)
Molybdenum (Mo) contributes to the improvement of strength and toughness, and also contributes to ensuring stable strength at room temperature or high temperature.
The molybdenum is preferably added in 0.01 to 0.03% by weight of the total weight of the steel. When the addition amount of molybdenum (Mo) is less than 0.01% by weight, the addition effect is insufficient. On the contrary, when the addition amount of molybdenum exceeds 0.03% by weight, the weldability is lowered, and the yield ratio is increased by precipitation of carbides.
Aluminum (Al)
Aluminum (Al) serves as a deoxidizer to remove oxygen in the steel.
The aluminum is preferably added at 0.03 to 0.05% by weight of the total weight of the steel. If the amount of aluminum added is less than 0.03% by weight, the deoxidation effect is insufficient. On the contrary, when the addition amount of aluminum exceeds 0.05% by weight, there is a problem of lowering the impact characteristics of the steel.
Copper (Cu)
Copper (Cu) is an effective element for increasing strength and improving toughness. In addition, copper contributes to the solid solution strengthening effect through constant content control together with silicon (Si) and manganese (Mn).
The copper is preferably added in 0.1 to 0.2% by weight of the total weight of the steel. When the addition amount of copper is less than 0.1 weight%, the addition effect is inadequate. On the contrary, when the addition amount of copper exceeds 0.2 weight%, there exists a possibility that the surface characteristics of steel may fall.
Titanium (Ti)
Titanium (Ti) forms TiN upon reheating, inhibits austenite grain growth, and serves to refine the structure of the steel.
The titanium is preferably added in 0.02 ~ 0.05% by weight of the total weight of the steel. When the addition amount of titanium is less than 0.02% by weight, the addition effect is insufficient. On the contrary, when the addition amount of titanium exceeds 0.05 weight%, TiN precipitate will coarsen and the grain growth inhibitory effect will fall.
Boron (B)
Boron (B) is a strong hardenable element and contributes to the improvement of strength of steel.
The boron is preferably added in 10 ~ 30ppm of the total weight of the steel. When the addition amount of boron is less than 10 ppm, the addition effect is insufficient. On the contrary, when the addition amount of boron exceeds 30 ppm, there is a problem of causing a material deviation due to grain boundary segregation and lowering the impact characteristic.
Nitrogen (N), Oxygen (O)
Nitrogen (N) and oxygen (O) are unavoidable impurities, and when contained in a large amount, nitrogen (N) and oxygen (O) become factors that lower the physical properties of the steel.
Therefore, in the present invention, the nitrogen and oxygen contents were limited to 100 ppm or less and 40 ppm or less, respectively.
Manufacturing method of track shoe steel
1 is a flow chart showing a method for manufacturing a track shoe steel according to an embodiment of the present invention.
Referring to FIG. 1, the illustrated steel manufacturing method includes a slab preparing step S110 and a hot rolling step S120. In addition, the hot rolling step S120 includes a reheating step S121, a hot rolling step S122, and a cooling step S123 in detail.
A cast
In the slab preparation step (S110), the aforementioned alloy composition, that is, carbon (C): 0.24 ~ 0.26% by weight, silicon (Si): 0.17 ~ 0.26% by weight, manganese (Mn): 0.95 ~ 1.1% by weight, phosphorus (P) : 0.018 wt% or less, Sulfur (S): 0.01 wt% or less, Chromium (Cr): 0.14 ~ 0.16 wt%, Nickel (Ni): 0.05 ~ 0.07 wt%, Molybdenum (Mo): 0.01 ~ 0.03 wt%, Aluminum (Al): 0.03 to 0.05% by weight, copper (Cu): 0.1 to 0.2% by weight, titanium (Ti): 0.02 to 0.05% by weight, boron (B): 10 to 30 ppm, nitrogen (N): 100 ppm or less, oxygen (O): Cast slabs composed of 40 ppm or less and the remaining iron (Fe) and other unavoidable impurities.
The cast steel may be produced by continuously casting a molten steel having the composition.
Hot rolling process
The hot rolling process includes a reheating step S121, a hot rolling step S122, and a cooling step S123.
In the reheating step (S121), the slabs having the alloy composition are reheated to re-use segregated components during casting.
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 other hand, when the reheating temperature is higher than 1250 占 폚, the austenite grains are coarsened and it is difficult to secure the strength of the steel to be produced.
Next, in the hot rolling step (S122), the reheated cast steel is rolled. At this time, the reheated cast steel may be rolled in the shape of a predetermined track shoe in the hot rolling step.
It is preferable to perform finishing rolling temperature at the time of hot rolling 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 produced is lowered.
Next, in the cooling step (S123), the rolled steel is cooled to the cooling end temperature. Cooling may be performed by a water cooling method of pouring to the rolled steel or an air injection method of injecting air to the surface of the rolled steel. The cooling rate may present about 0.1-20 ° C./sec, but is not necessarily limited thereto.
Cooling end temperature is preferably 450 ~ 600 ℃. If the cooling end temperature is less than 450 ℃ yield strength may increase due to the formation 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.
On the other hand, the inventors of the present invention, as a result of a long study, found that the sulfur content (wt%) and 25 ℃ impact value in the track shoe steel having the composition of the present invention satisfies the relationship as shown in Equation 1 below.
[Equation 1]
25 ℃ Impact Value (Kgfm / cm 2 ) = -51.21 x (7.023 x [S] -0.003) + 9.66
(In Equation 1, [S] is the weight% of sulfur in the composition.)
Equation 1 corresponds to an equation derived from Equations 2 and 3 below.
According to Equation 1, when the content of sulfur in the composition is determined, it is possible to predict the impact value at 25 ° C. On the contrary, when the target impact value is determined at 25 ° C, the content of sulfur may be predicted and adjusted during steel production.
In addition, it was found that the content of sulfur (wt%) and the content of sulfide (wt%) formed in the steel satisfy the relationship as shown in Equation 2 in the track shoe steel having the composition of the present invention.
&Quot; (2) "
25 ℃ Impact value (Kgfm / cm 2 ) = -51.21 x [sulfide] + 9.66
(Sulfide in Equation 2 is the weight percentage of sulfide formed in steel)
According to Equation 2, it is possible to predict the impact value of 25 ℃ if the content of the sulfide formed in the steel can be known.
In addition, it was found that the content of sulfur (wt%) and the content of sulfide (wt%) formed in the steel in the track shoe steel having the composition of the present invention satisfy the following equation (3).
&Quot; (3) "
[sulfide] = 7.023 x [S] -0.003
(Sulfide in Equation 3 is the weight% of sulfide formed in the steel, [S] is the weight% of the sulfur in the composition)
According to Equation 3, when the content of sulfur in the composition is determined, it is possible to predict the content of sulfides formed in the steel.
In the case of Equation 3, as a result of changing the content of various alloying components for the track shoe steel having a composition according to the present invention, it is found that the content of sulfides formed in the steel is changed at a constant rate according to the change of the content of sulfur in particular. It was derived by linear regression analysis.
In addition, in the case of Equation 2, the track shoe steel having a composition according to the present invention was found to change at a constant rate of 25 ℃ according to the change in the content of sulfide, especially among the various inclusions, it was derived by linear regression analysis .
On the other hand, the steel for track shoes is required that the impact value of 25 ℃ at least 7Kgfm / cm 2 or more.
Substituting this in Equation 2, it is preferable that sulfides of 0.052% by weight or less are formed in the steel. In addition, when the numerical value is substituted into Equation 3, the content of sulfur in the steel composition is preferably 0.008 or less.
However, in order for the sulfur content to be less than 0.004% by weight, the sulfur content must be managed in a very small amount, which can greatly increase the steel manufacturing cost. In view of this point, the content of sulfur is preferably 0.004 to 0.008% by weight. In addition, when the minimum content of sulfur is applied to Equation 3, the sulfide formed in the steel is at least 0.025% by weight.
Therefore, the sulfide formed in the steel can be 0.025 to 0.052% by weight. When the minimum sulfide value is substituted into Equation 2, the 25 ° C impact value at 0.025% by weight of sulfide is 11 Kgfm / cm 2 .
Therefore, if the sulfur content in the steel for track shoes according to the present invention is 0.004 ~ 0.008% by weight, the sulfide content formed in the steel may be 0.025 ~ 0.052% by weight, and further in the range of 7 ~ 11Kgfm / cm 2 at 25 ℃ Impact values can be expected.
In addition, if a target value for the 25 ℃ impact value is set, it is possible to predict the appropriate sulfur content based on this.
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. Preparation of specimens
13 cast pieces having the composition shown in Table 1 were prepared. Then, after reheating at 1200 ℃ for 2 hours, hot rolling to the finish rolling temperature 800 ℃, and cooled to 520 ℃ at a cooling rate of approximately 5 ℃ / sec using an air injection method.
Table 1 (Unit: wt%, except B, N and O ppm)
For the steel specimens 1 to 13, the inclusions were measured by JIS G 0555 method, Rockwell hardness and 25 ° C. Charpy impact value were measured, and the results are shown in Table 2.
Figure 2 shows the 25 ℃ impact value according to the content of sulfide (sulfide) for the track shoe steel specimens according to the present invention.
Referring to FIG. 2, it can be seen that 25 ° C. impact values are concentrated in a line representing Equation 2 according to a sulfide content change formed in each steel specimen, and the closer to the crystal coefficient R 2 , 1, the regression model. High suitability for)) was 0.822.
[Table 2]
※ In Table 2, Globular means spherical inclusions, and A / S means the aspect ratio of sulfide having a long stretched shape by rolling.
Figure 3 for the track shoe steel specimens according to the invention, shows the content of sulfide according to the content of sulfur.
Referring to Figure 3, it can be seen that the sulfide content formed in the steel is concentrated in the line representing the equation (3) according to the change in the sulfur content of each steel specimen, the crystal coefficient (R 2 ) is 0.781 appear.
2 and 3, although the respective data do not correspond exactly to Equation 2 and Equation 3, considering that the crystal coefficient is very high as 0.7 or more, the predicted value almost equal to the actual 25 ° C. impact value or sulfur content is obtained. It can be seen that.
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: cast preparation step
S120: hot rolled stage
S121: Reheating Step
S122: hot rolling stage
S123: Cooling Step
Claims (9)
Steel having a 25 ℃ impact value according to the formula (1).
[Equation 1]
25 ℃ Impact Value (Kgfm / cm 2 ) = -51.21 x (7.023 x [S] -0.003) + 9.66
(In Equation 1, [S] is the weight% of sulfur in the composition.)
The sulfur is
Steel, characterized in that contained in 0.004 to 0.008% by weight.
The steel
Steel material characterized by the formation of 0.025 to 0.052% by weight of sulfide.
Steel having a 25 ℃ impact value according to the formula (2).
&Quot; (2) "
25 ℃ Impact value (Kgfm / cm 2 ) = -51.21 x [sulfide] + 9.66
(Sulfide in Equation 2 is the weight percentage of sulfide formed in steel)
The sulfide is
Steel, characterized in that formed from 0.025 to 0.052% by weight.
The steel is
Steel, characterized in that the sulfide according to the formula (3) is formed.
&Quot; (3) "
[sulfide] = 7.023 x [S] -0.003
(Sulfide in Equation 3 is the weight% of sulfide formed in the steel, [S] is the weight% of the sulfur in the composition)
The sulfur is
Steel, characterized in that contained in 0.004 to 0.008% by weight.
After reheating the cast steel at 1150 ~ 1250 ℃, hot rolling to a finish rolling temperature 700 ~ 950 ℃, and then cooling to 450 ~ 600 ℃; including,
According to the following Equation 1, the steel manufacturing method, characterized in that for determining the content of the sulfur (S) from the target 25 ℃ impact value (Kgfm / cm 2 ).
[Equation 1]
25 ℃ Impact Value (Kgfm / cm 2 ) = -51.21 x (7.023 x [S] -0.003) + 9.66
Where [S] is the weight percent of sulfur in the composition
The target 25 ℃ impact value
Steel manufacturing method characterized in that the selected within 7 ~ 11 Kgfm / cm 2 .
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR101707340B1 (en) * | 2015-12-28 | 2017-02-15 | 현대제철 주식회사 | Chain steel and manufacturing method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR101707340B1 (en) * | 2015-12-28 | 2017-02-15 | 현대제철 주식회사 | Chain steel and manufacturing method thereof |
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