KR102158988B1 - Special steel alloys for continuous casting equipment and rolls of continuous casting equipment comprising the same - Google Patents

Abstract

C 0.05 to 0.15 wt%, Si 0.3 to 1.0 wt%, Mn 0.8 to 2.5 wt%, Cr 11.5 to 15.0 wt%, Ni 2.2 to 5.0 wt%, Mo 1.0 to 2.8 wt%, V 0.1 to 0.5 wt%, N It provides a special steel alloy for a performance equipment made of 0.01 to 1.0% by weight, balance Fe and other inevitable impurities, and a roll for a performance equipment made of the same.

Description

Special steel alloys for continuous casting equipment and rolls of continuous casting equipment comprising the same}

The present invention relates to a special steel alloy for a playing facility used in a roll material for a playing facility, and a roll for a playing facility made of the same, and a special steel alloy for a playing facility with improved heat resistance, corrosion resistance, and high temperature hardness, and thereby increasing the equipment life and productivity. It is about a roll for playing equipment that is used.

The continuous casting process refers to a process of continuously injecting molten steel into a mold of a certain shape to continuously pull out the reaction-hardened cast plate into the lower part of the mold. The configuration of the playing equipment for performing the playing process is shown in FIG. 1.

Referring to Figure 1, the playing equipment 10 is provided in a ladle 12 containing molten steel, a tundish 14 supplying molten steel through an injection nozzle connected to the ladle 12, and a tundish 14 It includes a mold 16 that receives the molten steel and initially solidifies it into a predetermined shape, and a strand located under the mold 16 to transport and cool the unsolidified cast piece S.

The segment 18 constituting the strand includes a plurality of rolls (R) arranged to face each other, and a pressing force can be applied to the cast piece (S) by adjusting the separation distance between the rolls, and the cast piece by rotation It has a function of transporting.

The roll (R) of the playing equipment may cause cracks, hot abrasion or corrosion, deformation of the roll, etc. due to thermal fatigue during operation of the equipment due to continuous contact with the hot cast steel, and accordingly, the life of the roll may be shortened. . In addition, due to this, the maintenance cost of the playing equipment may increase, and problems such as a decrease in surface quality of the cast steel, non-uniform thickness of the cast steel, and decrease in productivity may occur.

To solve this, the roll (R) of the playing equipment may be made of an alloy steel having excellent surface properties by a hardfacing method in which a functional film is formed using thermal spray coating or growth welding. Therefore, there is a further need for technology development of an alloy material that has excellent bonding performance by melting of the welding material and the base material, and can increase heat resistance, corrosion resistance, and high temperature hardness to the roll surface.

Korean Patent Registration No. 10-1360552 (Registration date: 2014. 02. 03.) Korean Patent Laid-Open Patent No. 10-2014-0118698 (Publication date: 2014. 10. 08.) Japanese Laid-Open Patent No. 2007-136509 (Publication date: 2007. 06. 07.)

It is an object of the present invention to provide a special steel alloy for a performance roll playing equipment having excellent bonding performance by melting with a base material and having improved heat resistance, corrosion resistance, and high temperature hardness.

In addition, another technical problem to be achieved by the present invention is that by providing the special steel alloy for playing equipment of the present invention as a solvent for a hard face that strengthens the surface of a playing roll, cracks due to thermal fatigue, hot wear or corrosion, and damage to the roll It is an object of the present invention to provide a roll for playing equipment that can reduce deformation and the like and improve the equipment life and productivity of the playing equipment.

The object of the present invention is not limited to the above-mentioned object, and other objects that are not mentioned will be clearly understood by those of ordinary skill in the art from the following description.

In order to solve the above problem, the present invention is C 0.05 to 0.15 wt%, Si 0.3 to 1.0 wt%, Mn 0.8 to 2.5 wt%, Cr 11.5 to 15.0 wt%, Ni 2.2 to 5.0 wt%, Mo 1.0 to 2.8 wt% %, V 0.1 to 0.5% by weight, N 0.01 to 1.0% by weight, balance Fe and other unavoidable impurities can provide a special steel alloy for playing equipment.

The special steel alloy for the playing equipment may be of 0.04 to 0.1% by weight of N.

The special steel alloy for the playing equipment may be one containing 5 to 10% of ferrite.

The special steel alloy for playing equipment may have a chromium equivalent (Cr _eq ) of 10 to 22 defined by the following equation.

Cr _eq = Cr + Mo + 1.5Si + 0.5Nb +2Ti

The special steel alloy for playing equipment may have a nickel equivalent (Ni _eq ) defined by the following formula and a chromium equivalent (Cr _eq ) equivalent ratio (Cr _eq /Ni _eq ) to a nickel equivalent (Ni _eq ) of 1.3 to 3. have.

Ni _eq = Ni + 30C + 0.5Mn

The special steel alloy for the playing equipment may be one having a Rockwell hardness of 40 to 45 HRC.

In addition, in order to solve the above problems, the present invention can provide a roll for playing facilities made of a special steel alloy for playing facilities.

The special steel alloy for playing equipment for a playing roll according to an embodiment of the present invention has excellent bonding performance by melting with the base material, thereby improving heat resistance, corrosion resistance, and hardness, and the special steel alloy for playing equipment is hard-faced on the surface as a solvent. Rolls for performance equipment are cracks due to heat fatigue, hot wear or corrosion, By reducing the deformation, etc., there is an advantage that the equipment life and productivity of the playing equipment can be improved.

1 is a view showing a typical playing equipment,
2 is a graph showing the chromium equivalent (Cr _eq ) and the nickel equivalent (Ni _eq ) of the special steel alloy for playing equipment according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided as examples in order to sufficiently convey the spirit of the present invention to those skilled in the art to which the present invention pertains. Therefore, the present invention is not limited to the embodiments described below and may be embodied in other forms. In addition, in the drawings, the length and thickness of layers and regions may be exaggerated for convenience. The same reference numbers throughout the specification denote the same elements.

1 is a view showing a typical playing equipment, Figure 2 is a graph showing the chromium equivalent (Cr _eq ) and nickel equivalent (Ni _eq ) of the special steel alloy for playing equipment according to an embodiment of the present invention.

Special steel alloy for playing equipment according to an embodiment of the present invention is C 0.05 to 0.15 wt%, Si 0.3 to 1.0 wt%, Mn 0.8 to 2.5 wt%, Cr 11.5 to 15.0 wt%, Ni 2.2 to 5.0 wt%, Mo 1.0 To 2.8% by weight, V 0.1 to 0.5% by weight, N 0.01 to 1.0% by weight, the balance Fe and other unavoidable impurities.

In the special steel alloy for playing facilities, C (carbon) can improve high temperature strength and creep strength by combining with elliptical elements to form carbides. In order to secure precipitation of carbides according to each composition of the embodiment of the present invention, 0.05 It may contain to 0.15% by weight. If the content of C exceeds 0.15% by weight, it is preferable to have a range within the above upper limit, since an excess carbide is formed and the formation of carbide is coarsened and ductility is reduced, and a reinforcing layer cannot be obtained. If it is less than the weight %, the amount of carbon forming carbide is small, so that a structure capable of obtaining the desired hardness and strength may not be formed.

Si (Silicone) is an element with strong oxidizing power and acts as a deoxidation to remove oxygen from molten steel.It can be contained to improve the oxidation resistance of special steel alloys for playing facilities.Since excessive inclusion may reduce toughness, 0.3 to 1.0 It may be contained in a composition ratio of weight percent.

In addition, Mn (manganese) combines with oxygen and sulfur in the molten steel to form sulfides and oxides, which are partially removed along with slag, and Mn (manganese) plays a role in stabilizing the grain area, but when it is contained in excess Since hot workability may be deteriorated, it is preferably contained in the range of 0.8 to 2.5% by weight depending on the weight ratio of each of the composition of the present invention.

Furthermore, Cr (chromium) may be contained in a proportion of 11.5 to 15.0% by weight for corrosion resistance of the special steel alloy for performance equipment. If it is less than 11.5% by weight, securing corrosion resistance may decrease, and if it exceeds 15.0% by weight, a ferrite structure may be formed at room temperature, resulting in a decrease in strength.

In the special steel alloy for playing facilities, Ni (nickel) is a component that stabilizes crystal grains and increases toughness, but if the content is excessive, it may cause an increase in cost rather than an effect of increasing toughness, so it is contained in a ratio of 2.2 to 5.0% by weight. It is desirable.

In addition, Mo (molybdenum) can improve high-temperature strength by solid solution strengthening, but can be contained in an amount of 1.0 to 2.8% by weight for hot workability, and V (vanadium) helps to form carbides or nitrides to improve high-temperature strength. However, since excessive formation of precipitates such as carbides and nitrides lowers hot workability, it is preferably contained in an amount of 0.1 to 0.5% by weight.

The special steel alloy for playing equipment may contain 0.01 to 1.0% by weight of N (nitrogen), and further may contain 0.04 to 0.1% by weight. N improves high-temperature strength by solid solution strengthening, and when included with Mo, affects the improvement of corrosion resistance, and forms chromium (Cr) and nitride to improve high-temperature strength, and may contain 0.01 to 1.0% by weight.

As shown in area X of FIG. 2, the special steel alloy for playing equipment according to an embodiment of the present invention may further include ferrite, and further, may contain 5 to 10% ferrite.

The structure of the special steel alloy for playing equipment is determined according to the content of Cr and Ni, and the elements of Cr and Cr can activate the ferrite structure, and the elements of Ni and Ni can activate the austenite structure. Therefore, in general, a ferrite structure is formed as the chromium equivalent (Cr _eq ) equivalent ratio (Cr _eq /Ni _eq ) to the nickel equivalent (Ni _eq ) is increased, and the austenite structure may be activated as the equivalent ratio is small.

The special steel alloy for playing equipment may have a chromium equivalent (Cr _eq ) of 10 to 22 defined by the following equation.

Cr _eq = Cr + Mo + 1.5Si + 0.5Nb +2Ti ... … … … … … (One)

In addition, the casting facilities special steel alloy is nickel equivalent (Ni _eq) is be 1.3 to 3. chromium equivalent (Cr _eq) equivalent ratio (Cr _eq / Ni _eq) for the defined and nickel equivalent (Ni _eq) by the following equation is I can.

Ni _eq = Ni + 30C + 0.5Mn... … … … … … … … … (2)

For example, as shown in Figure 2, when the chromium equivalent (Cr _eq ) according to Equation (1) is 16 to 21, and the nickel equivalent (Ni _eq ) according to Equation (2) is 7 to 12, special steel for playing facilities The alloy may have a nickel equivalent (Ni _eq ) to a chromium equivalent (Cr _eq ) equivalent ratio (Cr _eq /Ni _eq ) of 1.3 to 3. This may include some austenite and ferrite structures in the martensite structure, and thereby, a special steel alloy for playing equipment with improved heat resistance, corrosion resistance, and hardness may be made with excellent bonding performance by melting with the base material.

In addition, the special steel alloy for playing equipment may be tempered at a temperature of 800 to 1020°F for 4 to 8 hours to reach Rockwell hardness HRC of 40 to 45. At temperatures below 800˚F, tempering does not occur sufficiently, and thus retained austenite remains, resulting in poor toughness and insufficient impact resistance. At temperatures above 1020˚F, the hardness is less than HRC 40, so sufficient hardness cannot be maintained.

Therefore, the roll for playing facilities provided with the special steel alloy for the playing facilities as a solvent reduces cracks, hot wear or corrosion, and deformation of the rolls due to heat fatigue, thereby improving the equipment life and productivity of the playing facilities.

Hereinafter, the special steel alloy for playing equipment according to the present invention will be described through the following experimental examples, and the following experimental examples are only examples for explaining the present invention, and the present invention is not limited thereto.

Experimental example

Special steel with the composition of 0.06% by weight of C, 0.6% by weight of Si, 2.3% by weight of Mn, 12.5% by weight of Cr, 4.2% by weight of Ni, 1.6% by weight of Mo, 0.3% by weight of V, 0.05% by weight of N, balance Fe and other inevitable impurities The alloy was prepared.

The special steel alloy was manufactured with a 3.2mm diameter wire, and the A36 base material was heated at around 250°C, and then grown and welded twice by submerged welding, and the special steel alloy was welded to the surface of the base material under conditions of 26 to 30V and 300 to 450A. I did. Thereafter, post-heat treatment was performed within the range of 250 to 300°C for 2 to 4 hours, and heat treatment was further performed to relieve residual stress. The process for relieving residual stress was heat-treated at 530° C. for 4 to 8 hours and then cooled to 200° C. by furnace cooling. Thereafter, the following tests were performed by cutting into specimens having sizes of 20mm *20mm *50mm and 12.5mm *12.5mm *20mm (width * length * height).

Comparative example

C 0.12% by weight, Si 0.4% by weight, Mn 1.2% by weight, Cr 13.5% by weight, Ni 2.5% by weight, Mo 1.2% by weight, V 0.18% by weight, Nb 0.18% by weight, balance Fe and other unavoidable impurities The alloy was prepared. Subsequently, after welding to the base material in the same process as in the experimental example, heat treatment was performed, and a specimen was prepared.

Test Example 1-Wear test

The amount of weight reduction was measured by performing a wear test on each specimen using the method of ASTM G65, respectively, for the special steel alloys for performance equipment provided from Comparative Examples and Experimental Examples. That is, after the above specimen was prepared, it was processed into a size conforming to ASTM G65 standard. After grinding the surface (#80), the initial weight was measured. And after the 6,000 wheel test, the weight was measured and the surface was polished, and the 6000 wheel test was again performed.

Test Example 2-Corrosion resistance test

The special steel alloys for performance equipment prepared from Comparative Examples and Experimental Examples were immersed in 6% iron chloride solution in a room temperature environment for 72 hours using the method of ASTM G48 A, respectively, and then the weight reduction ratio was measured.

Test Example 3-Tissue Experiment

The special steel alloy specimens for performance equipment prepared from Comparative Examples and Experimental Examples were polished and then etched in each Lepera etching solution for 90 seconds, and then magnified 200 times with an optical microscope and observed, and each microscopic structure was analyzed.

Test Example 4-Tempering hardness measurement

The special steel alloy for performance equipment prepared from Comparative Examples and Experimental Examples was maintained at a temperature of 800 to 1200°F for 4 to 8 hours and subjected to tempering by furnace cooling, and then its HRC hardness was measured to record the tempering HRC hardness for each temperature.

Test Example 5-Thermal fatigue experiment

The special steel alloy for performance equipment prepared from Comparative Examples and Experimental Examples was mounted on a test equipment equipped with a propane torch for heating the specimen and a water cooling nozzle for cooling, and rotated to perform a heating-quenching cycle 1,000 times, and then visually inspected surface damage. Was observed.

result

As a result of performing the ASTM G65 abrasion test, it was found that the amount of reduction after wear was smaller in the experimental example than in the comparative example, and the hardness of the special steel alloy for playing equipment of the present invention was more excellent. Even in the tempering hardness characteristics according to temperature, the hardness of the special steel alloy for playing equipment of the present invention, which was tempered at 800 to 1200˚F, was more excellent than HRC 40. However, at less than 800˚F, the comparative example showed high hardness.However, when tempering at this temperature, the tempering temperature was too low and the ductility and toughness were insufficient, and thus the impact resistance was insufficient, causing cracks in actual application. There was a problem.

In addition, it was found that the weight reduction ratio of the special steel alloy for playing equipment of the present invention to the 6% iron chloride solution was significantly lower than that of the comparative example, and thus the corrosion resistance was further improved than the conventional one. In the example of the present invention, when immersed in a 6% FeCl solution at room temperature for 72 hours, a weight reduction of 0.061 g/cc occurred, which was found to have 2.5 times superior corrosion resistance (40% of the comparative example) compared to the comparative example. Became.

Furthermore, as a result of visual observation in the thermal fatigue experiment, the special steel alloy for playing facilities of the comparative example showed overall surface damage, but the special steel alloy for playing facilities, which is an experimental example of the present invention, was able to observe insignificant surface damage compared to the comparative example.

In addition, in the result of observing the surface after the lepera etching with a microscope, it was clearly shown that the corrosion proceeded along the grain boundaries of the comparative examples, but in the experimental example, corrosion along the grain boundaries did not appear, and better corrosion characteristics were observed. . In other words, it was found that the special steel alloy for playing equipment of the present invention further improved corrosion resistance.

Therefore, it can be seen that the hardness, heat resistance and corrosion resistance of the special steel alloy for playing equipment of the present invention are improved by reducing the carbon content than the comparative example and containing nitrogen, and this results in cracks due to thermal fatigue, hot wear or corrosion, roll It is possible to provide a roll for playing equipment to reduce the deformation of the.

Although described above with reference to preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention within the scope not departing from the spirit and scope of the present invention described in the following claims. You will understand that you can do it.

10: performance equipment
12: ladle
14: Tundish
16: mold
18: segment

Claims (7)

C 0.05 to 0.15 wt%, Si 0.3 to 1.0 wt%, Mn 0.8 to 2.5 wt%, Cr 11.5 to 15.0 wt%, Ni 2.2 to 5.0 wt%, Mo 1.0 to 2.8 wt%, V 0.1 to 0.5 wt%, N 0.01 to 1.0% by weight, the balance consisting of Fe and other inevitable impurities,
Chromium equivalent (Cr _eq) is defined as the following equation is 10 to 22, and the nickel equivalent (Ni _eq) is defined by the following equation to the nickel equivalent (Ni _eq) chromium equivalent (Cr _eq) equivalent ratio (Cr _eq / on Ni _eq ) is 1.3 to 3, and the martensite structure includes austenite and ferrite structure, but the ferrite structure is 5 to 10 area% of a special steel alloy for playing equipment.
Cr _eq = Cr + Mo + 1.5Si + 0.5Nb + 2Ti
Ni _eq = Ni + 30C + 0.5Mn
The method of claim 1,
The special steel alloy for playing equipment is a special steel alloy for playing equipment, characterized in that N 0.04 to 0.1% by weight.
delete delete delete The method of claim 1,
The special steel alloy for playing equipment is a special steel alloy for playing equipment, characterized in that the Rockwell hardness is 40 to 45 HRC.
A roll for playing equipment made of a special steel alloy for playing equipment according to any one of claims 1, 2 and 6.

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