KR101104969B1 - Method of manufacturing the wheel - Google Patents

Abstract

The present invention relates to a load-bearing wheel and a method for manufacturing the same, the load-bearing wheel according to the present invention is an element C: 0.55 ~ 0.65w%, Si: 0.2 ~ 0.5w% Mn: 0.8 ~ 1.5w%, P: max. 0.04w% S: max. 0.04w%, V: 0.2 ~ 0.4w%, Fe: 96.87 ~ 98.23w%, and the alloy is made of a mixture; The load supporting wheel according to the present invention is a melting step of melting the alloy at 1,630 ± 50 ° C. to form a molten metal, and injecting the molten metal into a centrifugal mold to cast the desired wheel size and demold to cool. In the molding step, the molded product is gradually heated up to 860 ± 10 ° C. to maintain the conditions of 1 hour / inch + α, followed by quenching at a rate of 20 ° C. per hour up to 550-600 ° C., and then air-cooled to room temperature in air. The spheroidizing annealing step of making the carbides spheroidized, and the quenching step of quenching by quenching by spraying water on the running surface after maintaining the molded product undergoing the annealing step again to 840 ~ 880 ° C. for at least 5 hours. After the molding is heated to 450 ~ 500 ℃ again to maintain a minimum of 5 hours, it is made through a tempering step of tempering by air cooling. The load-bearing wheel of the present invention made by such a process has fewer shrinkage holes than the existing products, and the structure is dense, so that the overall tensile strength is improved, the allowable load is increased, and the product recovery rate is improved. have.

Load-bearing wheel, hoist wheel, bogie wheel

Description

Method of manufacturing the wheel for load support

The present invention relates to a method for manufacturing a load-bearing wheel used to support heavy loads, and in particular, there is no shrinkage hole, the structure is dense and the recovery rate is increased, while the overall tensile strength is improved while the toughness is increased, and the allowable load is increased. The manufacturing method of the wheel using the alloy for load bearing wheels which became high.

In general, a hoist, a crane, a trolley, or the like, which is used to transport a heavy object, is provided with a wheel to facilitate the transport while supporting a heavy load.

As such, the wheels provided in the equipment such as the hoist not only support heavy loads but also have to move in a load-supporting state, and therefore, the wheels require excellent mechanical properties, that is, high strength, high toughness and wear resistance.

For this reason, cast-iron wheels (SCMn2), forgings (S45C) and forgings (SSWQ1R) are generally used for load-bearing wheels such as hoists. The surface heat treatment method, in which the quenching depth is only about 1 mm, does not change the tensile strength.

In other words, SCMn2A has a low material cost, but welding repair is involved due to casting defects such as shrink holes, pin holes, and sand mixing. If welding repair is not complete, cracks are generated during high frequency heat treatment. There is a problem provided as a cause of the peeling phenomenon.

S45C has a problem that although the material cost is expensive, the raw material is consumed a lot, the recovery rate is low, the processing cost is high, and the peeling phenomenon occurs due to the hardness difference from the base material because only 1 mm of heat treatment is performed on the surface of the high frequency heat treatment furnace.

SCM440 has a high material cost but a low recovery rate and high processing cost. However, when the high frequency heat treatment is performed after finishing, only 1mm of the surface is heat-treated, meaning there is no meaning of expensive material, and there is a problem in that peeling phenomenon occurs due to the hardness difference between the base material.

In addition, SSWQ1R has a problem that the material cost is high, the recovery rate is low, the quenching depth is deep, but the elongation rate, the sectional shrinkage rate is low, and the allowable load is low.

Therefore, the material for making the existing load-bearing wheels as described above is easily worn or damaged, so the wheels need to be replaced frequently. Productivity is lowered because it can not be used, this phenomenon eventually led to a rise in the cost of the product.

Therefore, the present invention solves the problems caused by the conventional load-bearing wheel as described above, while increasing the production rate of the product compared to the input amount of raw materials in the manufacturing process, while increasing the recovery rate, high tensile strength and wear resistance and toughness It is an object of the present invention to provide an alloy for a load-bearing wheel and a method for manufacturing a wheel using the alloy that can be raised at the same time.

The load-bearing wheel of the present invention for achieving the above object is an element C: 0.55 ~ 0.65w%, Si: 0.2 ~ 0.5w% Mn: 0.8 ~ 1.5w%, P: max. 0.04w% S: max. It is made by mixing 0.04w%, V: 0.2 ~ 0.4w%, Fe: 96.87 ~ 98.23w%.

And the load-bearing wheel according to the present invention is to manage the alloy at 1,630 ± 50 ℃ dissolution step to make a molten metal, injecting the molten metal into a centrifugal mold casting and demoulding to the desired wheel size Cooling molding step, the molding is gradually heated up to 860 ± 10 ℃ again, maintaining the condition of 1 hour / inch + α, and then quenched at a rate of 20 ℃ per hour to 550 ~ 600 ℃, then in room temperature in air A quenching annealing step of allowing the carbide to be spheroidized by air cooling to quenching, quenching step of quenching by molding the sprayed water to the running surface to maintain at least 5 hours by heating the molded product after the annealing step again to 840 ~ 880 ° C, After the quenched molding is heated to 450 ~ 500 ℃ again to maintain a minimum of 5 hours, it is made through a tempering step of tempering by air cooling.

The wheel produced by the manufacturing method of the load-bearing wheel of the present invention made in this process is significantly smaller than the conventional product, the structure is dense and the recovery rate is increased, while the overall tensile strength is improved and the allowable load is increased The effect can be obtained.

As described above, the load-bearing wheel of the present invention is an element C: 0.55 ~ 0.65w%, Si: 0.2 ~ 0.5w% Mn: 0.8 ~ 1.5w%, P: max. 0.04w% S: max. It is made of alloy made by mixing 0.04w%, V: 0.2 ~ 0.4w%, Fe: 96.97 ~ 98.23w%.

Among the above elements, carbon (C) plays a role in changing the properties of iron as the most necessary impurity among the five impurities, and improves tensile strength by generating martensite when quenched by solid solution in austenite.

In general, the tensile strength of carbon steel is represented by B (Kgf / mm²) ≒ 20 + 100 × w% (C), the carbon content of the alloy used to make the load-bearing wheel according to the invention content of 0.55 ~ 0.65w The% alone forms a tensile strength of 80 kgf / mm² (MIN).

At 0.65 w% or more, the hardness of hardening is almost the same, and only wear resistance and impact resistance change. Carbon not only increases the hardness, but also stabilizes the austenite matrix, while expanding the area on the austenite matrix, allowing the addition of chromium, molybdenum, etc. to improve corrosion resistance. In addition, carbon combines with added chromium, molybdenum, vanadium, tungsten, titanium and the like to form a hard carbide, and the remainder is dissolved in the matrix structure surrounding the carbide.

As a result of testing the alloy according to the present invention as a test result, when the content of C increased to 0.63w% from 0.57w%, it was found that the tensile strength and hardness increased.

Therefore, in the alloy according to the present invention, the content of C is defined as 0.55 to 0.65w%.

Among the elements, manganese (Mn) acts as a deoxidation desulfurization agent, and in particular, greatly affects the process reaction according to the addition ratio with silicon, and removes dissolved oxygen in the molten metal during solidification.

Therefore, manganese is preferably added at least 0.5w% showing an effective effect as a deoxidation desulfurization agent, when the amount of manganese exceeds 2.0w% has a disadvantage in that wear resistance is reduced and brittleness is promoted, the content of manganese is 0.5 ~ 2.0 w% is preferred.

Manganese, on the other hand, increases hardenability, increases strength, has no tempering resistance, and is effective as a deoxidizer. In addition, MnS, which is a nonmetallic inclusion, is formed in the crystal grains by combining with sulfur (S), which is ductile and is elongated in the processing direction during plastic working.

In addition, manganese is combined with sulfur (S) to increase the machinability and prevent red brittleness. The pearlite becomes fine due to Mn, and the yield strength of carbon steel is improved by solidifying ferrite. Increasing effectiveness at low cost. When a large amount is added, the oxide reacts with the furnace material to precipitate.

Therefore, in the present invention, the content of manganese is defined as 0.80 to 1.50w%.

The element V (vanadium), on the other hand, refines grains, improves toughness, increases tempering resistance, and increases toughness upon secondary curing.

It makes carbides, improves creep resistance, and is a strong ferrite element. In addition, the affinity for carbon and nitrogen is relatively strong, forming a stable composite carbide to improve the high temperature strength and breaking strength.

When the amount of carbon is small, as the amount of vanadium increases, the grains become finer to stabilize the matrix phase. Therefore, the content of vanadium is preferably to be contained 0.2w% or more in order to show an effective effect to enhance the strength.

However, when the content of vanadium exceeds 2.0w%, vanadium is expensive, and therefore, it is disadvantageous in terms of economics, and there is a disadvantage in that oxidation of the metal protective film is dissolved.

Therefore, the content of vanadium is 0.2 ~ 2.0w%, but the addition of 0.25w% or less increases the quenchability and the addition of more than 0.3w% decreases the quenchability. Indeed, even in the experiment of the alloy according to the present invention, the measured values of elongation and section shrinkage when containing 0.35w% were higher than those when V contained 0.18w%.

For this reason, the alloy according to the present invention defines the content of V in 0.2 ~ 0.4w%.

In addition, the elemental Si (silicon) is effective as a deoxidizer because silicon oxide in molten steel is easily combined with Mn oxide and the like to facilitate flotation. Solid solution in the ferrite does not significantly affect the mechanical properties of the steel. When 2w% or more is added, toughness decreases and plasticity is impaired, but fluidity problems occur in the forming step, so that the addition of Si improves fluidity and solidification.

      For this reason, the content of Si in the alloy according to the present invention is defined as 0.2 ~ 0.5w%.

The remaining elements, P and S, depend on the amount of natural content of the individual elements in the alloying process. The maximum content is not more than 0.04 \ w% because S is Mn. In order to improve machinability by combining with Zn, Ti, Mo, etc., when Fe lacks Mn, it combines with Fe to form FeS inclusions. This FeS is very fragile and has a low melting point which causes cracking during processing.

In addition, P is not a problem if it is uniformly distributed in the steel, but usually forms a harmful compound called Fe₃P. The Fe₃P is extremely fragile and segregated so that the Fe₃P is not homogenized even after annealing, but increases in the processing of forging and rolling. It is an element harmful to steel, such as lowering impact resistance and promoting temper brittleness.

Therefore, in the alloy according to the present invention, two elements of S and P are max. Limit to ~ 0.04w%.

After mixing the elements constituting the alloy of the present invention configured as described above, and melted to a temperature of 1,630 ± 50 ℃ to make a molten metal, the molten metal is put in a mold and then molded into the desired wheel size by centrifugal casting method Cool to room temperature and mold.

As such, the centrifugal casting method is used in the forming process of the wheel according to the present invention. The centrifugal casting method is a casting method in which a mold is rotated at a high speed (300 to 3000 rpm) by compression and solidifying the mold inner surface by centrifugal force when the molten metal is injected and solidified. to be.

This centrifugal casting method,

(1) The molten metal is flowed into the mold at high speed to prevent poor fluidity and smooth texture.

(2) Due to the high pressure on the molten metal, the casting structure is compact and there are no pores. In addition, separation and removal of metal inclusions is rapid due to the specific gravity difference.

(3) No need for core, shorten working time and mass production.

(4) No hot water or hot water is necessary.

(5) There is almost no residual stress because there is no suppression of shrinkage during solidification.

Has such features.

In the mold used in the centrifugal casting method, a mold and a soft mold are mainly used, and the material of the mold is a heat resistant cast iron or a heat resistant steel to which molybdenum (Mo) is added.

In centrifugal casting, (1) distribute the molten metal evenly over the entire surface of the mold, (2) directional solidify the molten metal from the mold surface to the inner surface, and (3) the inclusions in the molten metal It is necessary to adhere to the principle of gathering in order to obtain a uniform and sound casting. For this purpose, it is important to properly set the rotation speed, injection temperature and injection speed of the mold.

The injected molten metal undergoes directional solidification from the outside, whereby the outer periphery is separated from the mold surface by the contraction and a gap is formed therebetween. The solidified layer is subjected to tensile stress by the centrifugal force acting on the inner molten metal. At this time, if the rotational speed is too large or the injection temperature is too high, hot cracking occurs in the longitudinal direction or the circumferential direction.

In addition, if the rotational speed is too small or the injection speed is too large, the centrifugal force is insufficient, causing dropping. This causes rapid internal oxidation, hinders directional coagulation, and can also cause shrinkage pores.

In view of the above circumstances, in the manufacturing process of the wheel according to the present invention, as described above, the alloy is managed at a melting temperature of 1,630 ± 50 ° C., and is set at a tapping temperature of 1,590 ± 50 ° C. and an injection temperature of 1,560 ± 50 ° C. to work.

The work is preheated to the mold in the range of 200-250 ° C., and the mold is pre-coated with coated sand. After about 1630 ℃ of molten metal is transferred using a preheated ladle (Laddle), it is injected at a temperature of about 1550 ~ 1570 ℃ centrifugal casting.

When manufactured using the centrifugal casting method as described above, there is an advantage that shrinkage pores are eliminated, the structure is dense, and the recovery rate is higher than the existing products.

In this way, the molded product formed by centrifugal casting is transformed from dendrite destruction and casting structure into a stable matrix structure, and spheroidizing annealing is performed to spheroidize while cutting the precipitated carbide, thereby depositing about 80% of carbide. To give toughness.

When the carbide surrounds the grain boundary, the material becomes generally weak. In this case, when the heat treatment is performed to spheroidize the carbide, the toughness is increased while maintaining the strength. In addition, spheroidization of carbides is necessary to improve mechanical properties such as plastic working and cutting property. The practice implemented for this purpose is spherical annealing.

In the present invention, the casting made through the centrifugal casting method is gradually heated again to 860 ± 10 ℃, 60 to 90 minutes in a state that the temperature (860 ± 10 ℃) to a depth of 1 inch (inch) inside the casting After the conditions are maintained, cooling is again performed at a rate of 20 ° C. per hour up to 550 ° C. to 600 ° C., followed by slow cooling (air cooling) to room temperature in air to form carbides.

When the spheroidizing annealing is performed through such a process, cracking may occur while the brittleness becomes weak while performing heat treatment to obtain high strength, but the product according to the present invention is a spherical structure, so that no crack is generated and the toughness is increased. You can get it.

After the annealing step is heated again to 840 ~ 880 ℃ to maintain for at least 5 hours, and then spray spray water to quench by spraying water on the running surface of the wheel (spray quenching) step, thus spray quenching When the water cooling stage is carried out, the water cooling stage is abnormally quenched, the other end is air cooled, and only the required surface layer can be rapidly hardened.

On the other hand, the cooling rate is partially different according to the size of the product, the type of the transformed phase is different. The mass effect, which differs in the effect of heat treatment according to the size of the material, can be reduced by spray quenching.

In addition, the residual stress generated by heat treatment causes heat treatment cracking or fatigue fracture, but the compressive stress on the surface improves the fatigue strength of the product within the range where cracking does not occur. Normally, residual stress due to tempering is caused by thermal stress during quenching or by stress accompanying phase transformation.

When the steel is quenched, the surface is cooled before the inside, and the product causes compressive residual stress on the outside, and the tensile residual stress on the center. This is called the thermal stress residual stress distribution, and the compressive residual stress is present on the surface to increase the fatigue strength.

Accordingly, in the present invention, by spray quenching as a heat treatment process of the wheel molding, it is also suitable for the circular shape of the product, the running surface (Tread surface) that touches the rail (rail) in order to roll the wheel in the hoist, etc. Can increase wear resistance.

Then, as a final process, the spray-quenched molding is heated to 450-500 ° C. again, followed by a tempering step of tempering by air cooling for at least 5 hours. Tempering is the operation of heating to a temperature below the transformation point and cooling at a moderate rate to reduce the hardness and increase the viscosity of the quenched steel. Quenched steel must be tempered and used immediately after hardening.

In the present invention, to give toughness to the product is carried out at 450 ~ 500 ℃. The change of the tissue by tempering depends on the change of heating temperature and time. Martensite rapidly changes to truesite at about 250 ° C. and is complete around 350 ° C. TrueCyte begins to change from around 400 ° C to solvites and ends at 600 ° C.

By tempering through this process, 1) it can increase the tensile strength of the entire heat treated area by improving the quenching depth, thereby increasing the allowable load, and 2) improving the quenching depth not only on the rail contact surface but also on the flange part. 3) The tissue of the rim (Rim) area that requires abrasion resistance and the tissue of the arm (Boss) that requires high toughness have an effect of obtaining a different form.

As a result of testing the mechanical properties of the wheel of the present invention made through the process as described above to the specimen of various configurations was as follows.

Types of Psalms

division C (W%) Si (W%) Mn (W%) P (W%) S (W%) V (W%) Psalm 1 0.63 0.35 1.00 0.018 0.020 0.30 Psalm 2 0.61 0.37 1.04 0.020 0.015 0.35 Psalm 3 0.58 0.33 0.96 0.016 0.020 0.33 Psalm 4 0.59 0.35 1.03 0.023 0.017 0.30 Psalm 5 0.62 0.38 1.06 0.019 0.014 0.38 Psalm 6 0.60 0.36 0.98 0.021 0.020 0.34 Psalm 7 0.62 0.35 1.05 0.020 0.018 0.28 Psalm 8 0.64 0.41 1.03 0.024 0.020 0.29 Psalm 9 0.57 0.38 0.95 0.018 0.016 0.33 Psalm 10 0.60 0.42 1.01 0.023 0.017 0.32 Psalm 11 0.55 0.36 0.99 0.019 0.021 0.31 Psalm 12 0.62 0.38 1.03 0.024 0.013 0.34 Psalm 13 0.61 0.35 1.06 0.027 0.020 0.32 Psalm 14 0.57 0.31 0.98 0.023 0.016 0.36 Psalm 15 0.60 0.34 1.03 0.018 0.014 0.31 Psalm 16 0.64 0.30 1.00 0.023 0.020 0.34 Psalm 17 0.62 0.33 0.97 0.018 0.013 0.33 Psalm 18 0.60 0.32 0.99 0.020 0.016 0.27 Psalm 19 0.62 0.38 1.03 0.026 0.020 0.30 Psalm 20 0.60 0.35 1.00 0.023 0.018 0.32

Mechanical properties according to the type of each specimen

division YP (Kgf / mm2) TS (Kgf / mm2) EL (w%) ROA (w%) HB Psalm 1 54.2 103.3 15.9 38.7 294.0 Psalm 2 53.7 102.1 15.8 39.1 290.0 Psalm 3 52.8 95.3 16.0 38.3 286.0 Psalm 4 52.6 96.6 15.8 38.9 288.0 Psalm 5 54.9 104.2 15.4 41.9 298.0 Psalm 6 52.8 100.2 15.7 40.5 290.0 Psalm 7 53.4 101.6 15.5 39.1 292.0 Psalm 8 54.9 104.6 15.8 38.2 302.0 Psalm 9 52.7 98.6 16.0 39.8 287.0 Psalm 10 52.3 100.5 15.2 38.6 307.0 Psalm 11 52.2 99.4 15.8 38.4 287.0 Psalm 12 53.3 101.1 15.6 38.3 310.0 Psalm 13 53.8 101.7 15.5 38.4 298.0 Psalm 14 52.6 99.6 14.8 39.9 285.0 Psalm 15 53.5 98.2 14.5 39.2 286.0 Psalm 16 54.0 103.5 15.2 39.8 317.0 Psalm 17 54.9 104.9 16.0 38.8 330.0 Psalm 18 56.3 106.1 15.4 39.6 293.0 Psalm 19 54.6 103.9 15.9 39.3 286.0 Psalm 20 53.8 102.7 16.0 40.2 290.0

YP: Yield Point

TS: Tensile Strength

ES: Elongation

ROA: Reduction of Area

H.B: Hardness Brinell

Claims (2)

delete Element C: 0.55 to 0.65w%, Si: 0.2 to 0.5w% Mn: 0.8 to 1. 5 w%, P: max. 0.04w% S: max. 0.04w%, V: 0.2 ~ 0.4w%, Fe: 97.17 ~ 98.23w% are mixed and dissolved at 1630 ± 50 ℃ to make molten metal, and the molten metal is injected into centrifugal mold to Molding step of casting and demolding to size and cooling to produce a molded product, the molded product in the molding step is gradually heated up to 860 ± 10 ℃ again to maintain 60 to 90 minutes, 20 ℃ per hour to 550 ~ 600 ℃ After cooling by thickening, and then air-cooling to room temperature in air, the spheroidizing annealing step to form a carbide spheroidized, and the molded product subjected to the annealing step is again heated to 840 ~ 880 ℃ to maintain a minimum of 5 hours Quenching step of quenching by spraying water to the running surface, and heating the quenched molding again to 450 ~ 500 ℃ to maintain a minimum of 5 hours, then load support including tempering step of tempering by air cooling Method of producing a wheel