KR100626206B1 - Special steel as material for machining steel and manufacturing process thereof - Google Patents

Abstract

In the present invention, carbon (C) 0.60 to 0.90% by weight, silicon (Si) 0.50 to 1.50% by weight, manganese (Mn) 0.40 to 1.00% by weight, nickel (Ni) 6.0 to 7.5% by weight, chromium (Cr) 23 to 28 It relates to a special steel as a material for steel processing tools, its use and manufacturing method, consisting of a weight percent, molybdenum (Mo) 0.50 to 2.00 weight percent and the remaining iron (Fe) and other unavoidable impurities.

The special steel of the present invention exhibits excellent heat resistance, corrosion resistance, abrasion resistance, impact resistance, oxidation resistance and precision even when used for a long time in high temperature, high pressure and high impact environment.

Special Steel, Guide Guide, Cutting Knife, Heat Resistance, Wear Resistance, Impact Resistance

Description

SPECIAL STEEL AS MATERIAL FOR MACHINING STEEL AND MANUFACTURING PROCESS THEREOF

The present invention relates to a special steel as a raw material for steel processing tools and a manufacturing method thereof.

Specifically, the present invention relates to a special steel used as a material such as a wire guide guide in a wire rod process, a guide guide for deformed steel in a hot rolling process, or a billet cutting knife in a steelmaking process and a continuous casting process, and uses and manufacturing methods thereof. It is about.

The manufacture and processing of steel is generally done over a long period of time in high temperature environments. In this case, the general iron alloy steel is softened and surface oxidized as well as annealed when exposed to a high temperature environment even though its hardness at room temperature is high. Therefore, steel processing tools made of such iron alloy steel cannot be used for a long time especially at high temperatures. . Therefore, special steels having other element (s) added to carbon steels are generally used for the above applications.

Generally, the special steel refers to a steel having special properties suitable for each case by alloying one or two or more special elements to carbon steel. Special elements for such alloys include nickel (Ni), chromium (Cr), manganese (Mn), tungsten (W), cobalt (Co), vanadium (V), silicon (Si), and the like. When all the alloys are selectively added in an appropriate amount, the original properties may be improved and improved, and at the same time, special properties different from the unadded carbon steels may be exhibited.

In other words, the properties of special steels vary depending on the alloying elements. When looking at the properties of general alloying elements, nickel increases toughness, increases oxidation resistance, nonmagnetic properties, low transformation point, high temperature impact resistance, and chromium has corrosion resistance and abrasion resistance. Molybdenum prevents tempering properties, Tungsten increases hardness and tensile strength at high temperatures, Copper increases oxidation resistance in air, Silicon has electromagnetic properties and heat resistance is improved. Manganese is one of the deoxygenating elements, and is effective for enhancing the solid solution. Cobalt plays a role in improving hot rolling properties, and vanadium can withstand high thermal shocks, thereby imparting heat resistance and corrosion resistance to the alloy. However, increasing the alloying amount of the above elements is not superior to the above properties, and will exhibit better properties when alloying the appropriate amount.

By alloying the appropriate amount of the above elements to produce a special steel according to the required purpose, structural steel, nickel-chromium steel, nickel-chromium-molybdenum steel, chromium-molybdenum steel, manganese-chromium steel is used, and as a hardened surface hardening steel Low carbon steel is used, but when demanding better performance, special steel containing nickel, chromium, molybdenum, tungsten, vanadium, etc. is used, and high carbon steel is used as tool steel.

The present invention relates to a material for steel processing tools among the special steels as described above, and those shown in Table 1 are known in heat-resistant special steels conventionally used.

division Standard symbol C Si Mn Ni Cr Mo Remarks SUS series SUS 440C 0.95-1.20 1.00 or less 1.00 or less 0.60 or less 16-18 - Martensitic Heat Resistant Steel (Heat Resistant, Wear Resistant) SUH 36 0.48-0.58 0.35 or less 8.00 to 10.00 3.25-4.50 20 to 22 - N: 0.35 ~ 0.50 Austenitic Heat Resistant Steel (Heat Resistant, Wear Resistant, Impact Resistant) Heat Resistant Steel SCH 12 0.20 to 0.40 2.00 or less 2.00 or less 8 to 12 18 to 23 - Heat resistant steel (heat resistant, corrosion resistant) SCH 24 0.35-0.75 2.00 or less 2.00 or less 33 to 37 24 to 28 - Heat resistant steel (heat resistant, corrosion resistant) Spheroidal graphite cast iron FCD 500-7 2.5 or more - - - - - Tensile strength: 500N / mm ² or more Strength: 320N / mm ² or more Elongation: 7% or more Hardness: 150 ~ 230HB Base structure: Ferrite + Pearlite Alloy tool steel SKD 61 0.32 ~ 0.42 0.8 to 1.2 0.5 or less - 4.5 to 5.5 1.0 to 1.5 V: 0.8-1.2 die casting die. Extrusion dies. ① Since SUS440C material is martensitic, it is a knife material. ② SUH36 is a heat-resistant steel material. ③ SCH12 and SCH24 materials are heat resistant steel materials. ④ FCD500-7 material is spheroidal graphite cast iron material. ⑤ SKD61 material is alloy tool steel and it is a material for hot die.

However, none of the heat-resistant special steels have the required level of heat resistance, oxidation resistance, abrasion resistance, impact resistance and corrosion resistance in high temperature, high pressure, high impact environment such as steel processing process, and severe hardness when used in high temperature environment for a long time Degradation occurs. For this reason, when using the conventional special steel, the wear of the processing equipment is severe and must be replaced from time to time, which must be reworked, resulting in a decrease in production efficiency.

The present invention has been made in order to solve the above problems, the purpose of the special steel used as a material for steel processing tools to maintain excellent heat resistance, oxidation resistance, wear resistance, impact resistance and corrosion resistance even in high temperature, high pressure and high impact environment have.

That is, an object of the present invention is to provide a special steel as a material that is used as a material for steel processing tools, and maintains excellent heat resistance, oxidation resistance, wear resistance, impact resistance, precision and corrosion resistance in high temperature, high pressure and high impact environments.

Another object of the present invention is to provide a special steel as a wire rod guide material in particular in the wire rod process.

It is still another object of the present invention to provide a special steel as a guide material for deformed reinforcing bar in hot rolling process.

Another object of the present invention is to provide a special steel as a billet cutting knife material, in particular in a steelmaking process or a continuous casting process.

Another object of the present invention is to provide a method for producing the special steel.

Another object of the present invention is to provide a special steel produced by the above production method.

In order to achieve the above object, the present inventors controlled the additive element and its content and repeated experiments, and unexpectedly could not reach the conventional special steel, the material for steel processing tools having super heat resistance, ultra oxidation resistance, ultra corrosion resistance, ultra impact resistance and ultra wear resistance It came to invent a special steel as.

That is, the special steel as a material for steel processing apparatus of the present invention is 0.60 to 0.90% by weight of carbon (C), 0.50 to 1.50% by weight of silicon (Si), 0.40 to 1.00% by weight of manganese (Mn), 6.0 to 7.5% by weight of nickel (Ni). %, 23 to 28% by weight of chromium (Cr), 0.50 to 2.00% by weight of molybdenum (Mo) and the rest of the iron (Fe) and other inevitable impurities are its technical characteristics.

More preferably, the carbon content is 0.60 to 0.89% by weight, the silicon content is more preferably 0.50 to 1.19% by weight, the manganese content is more preferably 0.81 to 1.00% by weight, The molybdenum content is more preferably 0.76 to 2.00 wt%.

In addition, the special steel may be used as a wire guide guide material in the wire rod process, as a reinforcing bar guide guide material in the hot rolling process, or may be used as a billet cutting knife material in the steelmaking process or continuous casting process.

The present invention also provides a method consisting of the following steps as a method for producing the special steel:

Selecting and calibrating materials such as ferroalloy and dissolving them at a temperature of 1700 to 2000 ° C;

Injecting the melt into the mold after molding sand compounding;

Cooling it and then carrying out the process of desalination and tetradecay;

The solution is heat-treated at 1010 to 1150 ℃ to remove the stress and then machined.

In another aspect, the present invention provides a special steel for a steel processing tool manufactured by the manufacturing method.

First, the reason why the above-described member element has excellent heat resistance, oxidation resistance, abrasion resistance, impact resistance, precision and corrosion resistance in the extreme environment intended by the present invention is as follows.

First, the content of carbon in the constituents of the alloy of the present invention is close to eutectic steel and carbonizes a high content of chromium to form carbides. This chromium carbide has a hardness of 23 to 25 Hardness Rockwell "C" scale (HRC), which serves to fix the wear resistance of the final product.

In addition, since nickel has a high content, the transformation point of special steel is lowered to room temperature (20 ° C.) or less, so that it is not hardened by heat generated during material movement and softening does not occur, so it does not twist and wear even in a high temperature and high pressure environment. In other words, due to the large amount of nickel, the structure of the special steel becomes an austenite structure, nonmagnetic material, and the structure is composed of a body-centered cubic lattice. In addition, the special steel of the present application containing a large amount of nickel does not increase even if the hardness is increased by heat treatment, and the hardness does not decrease even after annealing treatment.

Furthermore, since the high content of nickel and chromium of the special steel of the present application imparts excellent heat resistance and oxidation resistance to the alloy, precision work can be performed at a high temperature for a long time, and in particular, excellent wear resistance is given.

On the other hand, the reason for the addition of each component element constituting the special steel as a raw material for steel processing apparatus of the present invention and the reason for numerical limitation are as follows.

First of all, carbon is an invasive employment element, and has a great influence on the formation of special steel texture. The carbon content of the present invention is adjusted to be close to the vacancy steel, and if the content is less than 0.60 wt%, the desired heat resistance and abrasion resistance cannot be obtained, and if it exceeds 0.90 wt%, the state is changed to the super vacancy steel. In addition, since the content of chromium for carbide formation is relatively high, hardness and abrasion resistance are increased, but it is susceptible to impact and easily cracks and breaks. In order to secure heat resistance, abrasion resistance and impact resistance which are effects of the present invention, 0.60 to 0.89% by weight is more preferable.

Silicon in steel is one of the deoxygenated elements with electromagnetic properties and affects the coefficient of thermal expansion and strength. If the content of silicon is less than 0.50% by weight, there is a problem in the chemical reaction of other elements due to the lack of deoxidation. If the content of silicon is more than 1.50% by weight, the toughness is lowered due to excessive silicon content and the coefficient of thermal expansion at high temperature is excessively increased. A significant drop in physical properties is caused. In order to achieve the effect peculiar to the present invention, 0.50 to 1.19% by weight is particularly preferable.

Manganese in steel is one of the deoxidizing elements and is useful for pearlite structure strengthening effect, and is added to ensure deoxidizing and hot workability. However, if the content is less than 0.40% by weight, not only the desired strength can be secured, but also a predetermined deoxidation effect cannot be obtained or the hot workability is inferior. And when the manganese content exceeds 1.00% by weight, the desired strength is secured, but the elongation is sharply reduced and the surface properties are poor. In order to ensure heat resistance and wear resistance of the present invention, 0.81 to 1.00% by weight is particularly preferable.

Nickel in steel generally increases toughness, oxidation resistance, nonmagnetic, low transformation point high temperature impact resistance, and especially imparts corrosion resistance and thermal shock resistance to the alloy. In particular, in the present invention, as described above, the A ₁ transformation point of the alloy steel is lowered to room temperature (20 ° C.) due to the high nickel content, so that hardening and softening do not occur when the material is moved, and the alloy steel itself is composed of a body-centered cubic lattice of austenite structure. There is a smooth surface and no change in hardness. As a result, the precision work can be performed for a long time even in high temperature. However, if the content is less than 6.0% by weight, the desired heat resistance and wear resistance cannot be secured, and when the content exceeds 7.5% by weight, workability is significantly reduced.

In steel, chromium is generally added to increase the reinforcement, corrosion resistance, and abrasion resistance of the alloy. In the present invention, particularly, as described above, a carbide formed with a high chromium content fixes the wear resistance of the alloy steel. Furthermore, due to the high content of chromium, heat and oxidation resistance are imparted to the alloy steel. However, if the content is less than 23% by weight, the desired heat resistance, oxidation resistance and wear resistance cannot be secured, and when it exceeds 28% by weight, workability is reduced as in the case of nickel.

Molybdenum in steels generally acts to prevent tempering properties, to impart reinforcing effects to the alloy, to increase heat resistance, and to specifically increase corrosion resistance to chemicals such as strong acids. In the present invention, industrial cooling water is usually sprayed. In the present invention, molybdenum is added to prevent corrosion by high temperature steam, thereby increasing the service life of special steel. Furthermore, in the present invention, in particular, like chromium, heat resistance is imparted to the alloy, thereby suppressing erosion or thermal oxidation of the present material at a high temperature, thereby improving product precision. However, if the content is less than 0.50% by weight, heat resistance, oxidation resistance, abrasion resistance, and impact resistance in the high temperature, high pressure, and high impact environments particularly desired in the present invention cannot be secured, and in particular, the corrosion resistance described above cannot be secured. This results in shortening the service life, on the contrary, in the case of more than 2.00% by weight, the workability is deteriorated, and the coefficient of linear expansion is excessively increased. In order to implement the characteristic effects of the present invention, 0.76 to 2.00% by weight is particularly preferable.

The special steel of the present invention containing the above elements has excellent heat resistance and corrosion resistance even in the harsh environment of high temperature, high pressure and high impact, and in particular, excellent wear resistance, oxidation resistance, precision and impact resistance, and excellent performance as a material for steel processing equipment. Exert.

In particular, the special steel as a material for steel processing apparatus of the present invention is suitable as a material such as wire guide guide in the wire rod process, release reinforcing guide guide in the hot rolling process and billet cutting knife in the steelmaking process or continuous casting process.

The manufacturing method of special steel as a material for steel processing apparatus consists of the following steps:

Selecting and calibrating materials such as ferroalloy and dissolving them at a temperature of 1700 to 2000 ° C;

Injecting the melt into the mold after molding sand compounding;

Cooling it and then carrying out the process of desalination and tetradecay;

The solution is heat-treated at 1010 to 1150 ° C. to remove the stress and then machined.

In particular, the production method of the present invention can be prepared by pre-melting a mother alloy containing elements with a significantly higher melting point than other elements before the main melting process.

In general, the melting process of special steel manufacturing adopts a single melting process in which each element is melted by heating to a high temperature capable of dissolving all necessary elements. However, molybdenum (melting point: 2622 ± 10 ℃) has a higher melting point than other elements. In addition, the heating cost is higher than necessary, and the melting point and the scattering point are different and the oxidization property is increased, resulting in segregation, which makes it difficult to obtain desired physical properties of the final product.

Therefore, the present invention can adopt a double melting process including a process of pre-dissolving each necessary element and iron to form a mother alloy, and the manufacturing method using the mother alloy is particularly efficient in the case of molybdenum having a high melting point among the required elements. .

Among the manufacturing methods of the present invention, a manufacturing method including a master alloy manufacturing process is as follows:

The required elements are selected and dissolved at a temperature of 1700-2000 ° C .;

Injecting the lysate into an ingot case;

After cooling, the case was shelled to obtain a master alloy;

Selecting and calibrating ferroalloys and master alloys and dissolving them at a temperature of 1700 to 2000 ° C;

Injecting the lysate into the mold after molding sand molding;

Cooling it and then carrying out the process of desalination and tetradecay;

The solution is heat-treated at 1010 to 1150 ° C. to remove the stress and then machined.

The special steel as a material for steel processing apparatus manufactured by the above steps is heat-resistant and corrosion-resistant, so even if it is used continuously for a long time at high temperature, the surface oxide film does not occur, so the precision of the produced product is high. This is a part of the conventional iron-based alloy steel, even if the hardness is high at room temperature, it is not only annealing at high temperatures, especially long time use, but also a significant increase compared to the fact that work is not possible due to softening and surface oxidation due to heating will be. That is, the material of the alloy steel of the present invention does not soften and surface oxidize at high temperatures, and therefore is very suitable for use as a steel processing tool, especially as a guide guide and billet cutting knife material. Among them, the billet cutting knife used in the continuous casting process can only be used about 15,000 times in the past, but when using the special steel of the present invention, it can be seen that the wear of the blade is extremely insignificant even after using 200,000 times or more. Excellent excellence has been proven. The above characteristics clearly show that when the special steel of the present invention is applied to the actual site, the replacement cycle of the processing tool can be extended, and the reworking cost can be lowered, resulting in high productivity and cost reduction effect.

Embodiments of the present invention are as follows.

Example 1

Powdered powdered 20 kg of iron-molybdenum (molybdenum content: 60% by weight) and 80 kg of scrap iron were dissolved at 1800 ° C., injected into an ingot case, cooled, and the shell was shelled to prepare a mixed master alloy of molybdenum and iron.

Example 2

The ferroalloy and the master alloy were screened and calibrated with the composition shown in Table 2, and then dissolved at a temperature of 1800 ° C., and then separately blended with a molding sand and injected into a molded mold. After cooling it, degassing and tetradecay processes were carried out, followed by solid solution heat treatment at 1100 ° C., followed by machining to obtain a wire guide guide as a final product.

Examples 3 to 5

Example 2 was repeated, but the composition of the special steel of each Example was adjusted as described in Table 2 below.

Comparative Examples 1 to 7

Example 2 was repeated, but the composition of the special steel of each comparative example was adjusted as described in Table 2 below. In Comparative Example 7 of the present comparative example, a conventional spheroidal graphite iron FCD500-7 was used.

Examples 6-9

Example 2 was repeated, but the composition of the special steel of each example was adjusted as described in Table 2 below to obtain a guide for releasing rebar in the hot rolling process as a final product.

Comparative Examples 8 to 14

Example 2 was repeated, but the composition of the special steel of each comparative example was adjusted as shown in Table 2 below to obtain a guide guide for deformed steel reinforcement in the hot rolling process as a final product. In the comparative example 14, the conventional spherical graphite cast iron FCD500-7 was used.

Examples 10 to 13

Example 2 was repeated, but the composition of the special steel of each example was adjusted as described in Table 2 below to obtain the final product billet cutting knife.

Comparative Examples 15 to 21

Example 2 was repeated, but the composition of the special steel of each comparative example was adjusted as described in Table 2 below to obtain the final product billet cutting knife. Comparative Example 21 of the present comparative example used SKD61 which is a conventional hot die material.

No. C Si Mn Ni Cr Mo Remarks Example 2,6,10 0.70 1.00 0.90 7.0 25 1.50 Example 3,7,11 0.70 1.30 0.90 7.0 25 1.50 Example 4,8,12 0.70 1.00 0.60 7.0 25 1.50 Examples 5,9,13 0.70 1.00 0.90 7.0 25 0.60 Comparative Example 1,8,15 0.25 1.00 0.90 7.0 25 1.50 Comparative Example 2,9,16 0.70 0.25 0.90 7.0 25 1.50 Comparative Example 3, 10, 17 0.70 1.00 0.20 7.0 25 1.50 Comparative Example 4, 11, 18 0.70 1.00 0.90 3.0 25 1.50 Comparative Example 5, 12, 19 0.70 1.00 0.90 7.0 20 1.50 Comparative Example 6, 13, 20 0.70 1.00 0.90 7.0 25 0.20 Comparative Example 7, 14 2.5 or more - - - - - Tensile strength: 500N / mm ² or more Strength: 320N / mm ² or more Stretching: 7% or more Hardness: 150 ~ 230HB Comparative Example 21 0.32 ~ 0.42 0.8 to 1.2 0.5 or less - 4.5 to 5.5 1.0 to 1.5 V: 0.8 ~ 1.2

Test Example 1

Table 3 shows the results of actual wire rod fabrication using the wire guide guides of Examples 2 to 5 and Comparative Examples 1-7. In Table 3, tonnage refers to the tonnage of a wire rod (5.6 φ) normal product manufactured using a set of wire guide guides.

No. Correction tonnage Example 2 1,570 Example 3 1,270 Example 4 1,290 Example 5 1,120 Comparative Example 1 420 Comparative Example 2 470 Comparative Example 3 630 Comparative Example 4 550 Comparative Example 5 510 Comparative Example 6 400 Comparative Example 7 310

Test Example 2

Table 4 shows the results of manufacturing actual deformed reinforcing bars using the respective deformed bar induction guides of Examples 6 to 9 and Comparative Examples 8 to 14. The correction tonnage in Table 4 refers to the tonnage of a normal rebar (10 mm) normal product manufactured using a set of deformed bar guides.

No. Correction tonnage Example 6 2,310 Example 7 1,870 Example 8 1,900 Example 9 1,640 Comparative Example 8 680 Comparative Example 9 620 Comparative Example 10 920 Comparative Example 11 810 Comparative Example 12 750 Comparative Example 13 590 Comparative Example 14 520

Test Example 3

The results of cutting the actual billets using the respective billet cutting knives of Examples 10 to 13 and Comparative Examples 15 to 21 are shown in Table 5 below. Each figure in Table 5 indicates the number of times a billet (150 × 150 mm) can be cut normally using one knife.

No. Count Example 10 209,800 Example 11 170,100 Example 12 172,800 Example 13 152,800 Comparative Example 15 57,000 Comparative Example 16 62,100 Comparative Example 17 84,400 Comparative Example 18 68,300 Comparative Example 19 73,700 Comparative Example 20 50,200 Comparative Example 21 15,400

It can be seen from Tables 3 to 5 that the special steel of the present invention shows remarkable heat resistance, abrasion resistance, impact resistance, oxidation resistance, precision and corrosion resistance compared to FCD500-7 and SKD61, which are materials for conventional steel processing tools.

This is a result of precisely adjusting the element and its content so that the microstructure of the special steel is suitable for the high temperature, high pressure, and high impact environment intended by the present invention, thereby having an excellent effect compared to the known steel processing material used in the prior art. It is to provide special steel

As described above, the special steel as a material for steel processing apparatus of the present invention has high heat resistance, abrasion resistance, impact resistance, oxidation resistance, precision and Corrosion resistance can be exhibited, and thus the present invention can provide a material which is particularly suitable for steel processing tools.

Claims (12)

0.60 to 0.89% by weight of carbon (C), 0.50 to 1.19% by weight of silicon (Si), 0.81 to 1.00% by weight of manganese (Mn), 6.0 to 7.5% by weight of nickel (Ni), 23 to 28% by weight of chromium (Cr), Special steel as a material for the production of wire guide guides, rebar guide guides or billet cutting knives, consisting of 0.76 to 2.00% by weight of molybdenum (Mo) and the remaining iron (Fe) and other unavoidable impurities. delete delete delete delete delete delete delete delete delete delete delete