KR100256367B1 - The manufacturing method for high chrome carbide line alloy and same product - Google Patents

Abstract

PURPOSE: Provided is a method for manufacturing Cr-rich overlay welding alloy of carbide-based having superior scratch resistance by controlling heat treatment condition and metal constituents. CONSTITUTION: The Cr-rich overlay welding alloy of carbide-based is manufactured by overlay-welding an overlay welding alloy comprising C 2.0-6.5wt.%, Cr 15-35wt.%, Mn 0.1-6wt.%, Si 0.1-2wt.%, 15wt.% or less at least one element selected from Nb, Mo, W, Ni, a balance of Fe and other inevitable impurities on the surface of a base metal; heat treating in the temperature range of 900 to 1100deg.C for 1-10hrs.

Description

Manufacturing method of high chromium carbide based growth weld alloy to improve scratch wear resistance

The present invention relates to a method for producing a high chromium carbide-based growth weld alloy used in fields requiring abrasion resistance, such as dredging equipment, crushing rolls, and more particularly, to a high chromium carbide-based growth weld alloy for improving scratch resistance It relates to a manufacturing method.

High chromium iron alloys have high wear resistance by depositing very high chromium carbides [(Cr, Fe) ₇ C ₃ ] with the hardness value of Hv 1,100-1,700 by the carbon and chromium elements contained in the alloy. It is a particularly good alloy. These high chromium iron-based alloys are used throughout industrial equipment in various product forms, such as cast and raised welded parts. In particular, the area of extreme wear caused by friction with soil and minerals, namely dredging equipment, crushed products of cement factory, raw materials of steel mills and screens of sintered ore, hopper, raw material loading part of thermal power plant, inside of ready-mixed concrete machine, etc. Used for

High chromium iron-based alloys with chromium carbides are very important materials in applications requiring wear resistance. These high chromium iron-based alloys are manufactured by casting or wet welding, and above all, they are inexpensive and excellent in wear resistance compared to other materials.

High chromium iron alloys are classified according to the type of matrix or chromium carbide surrounding the chromium carbide. In other words, the matrix structure surrounding the chromium carbide is classified into austenite, martensite, and pearlite high chromium abrasion alloys depending on whether it is austenite, martensite, or pearlite phase, and regardless of the matrix structure. The presence of primary carbides in carbides surrounded by matrix structures is classified into hypereutectic high chromium abrasion alloys and, if primary carbides are present without primary carbides, they are classified as secondary eutectic high chromium abrasion alloys.

Austenitic high chromium iron alloys have been chromium-carbonized by increasing the carbon content to 5% to date after the first 2% C + 8% Mn + 29.5Cr + Fe (rest) alloys were published in US Patents 1,671 and 384 in 1928. Abrasion resistance has been improved by increasing the quantity and increasing the hardness value slightly. Martensitic high chromium iron alloys were first developed in US Pat. No. 1, 245, 552 in 1917, 2.25-2.85% C + 0.5-1.25% Mn + 0.25-1.0% Si + 24-30% Cr + Fe (rest of HC250). By heat-treating the alloy, it has been known as a material having excellent scratch resistance under low stress. Since then, up to 5% of carbon and 35% of chromium, the matrix is austenite or martensite, and the matrix is commonly used in alloys surrounding primary chromium carbides.

These high chromium wear resistant alloys have been used in different alloy systems depending on the conditions of use and production method. That is, in the case of castings that have been studied for many years, only a hole-hole high chromium wear alloy is manufactured and used. This is the result of research showing that the wear resistance of the super masonry high chromium-based carbide which shows the best scratch resistance and the higher carbide amount when the amount of carbide is around 30% decreases as the amount of carbide increases (KH Zum Gahr and DV). Doane, Mettallurgical Transactions A Volume 11A, April 1980 p613-620) and over-vacuum high chromium-based alloys cause cracks during casting. In the case of sub-process high chromium abrasion alloys made from castings, alloys with austenitic matrix structures are used where the impact is severe and heat treated martensite matrix structures are used where the impact is low and heat resistance is required. Eggplant alloy is used.

On the other hand, in the case of over-vacuum high chromium carbide-based haze having a coarse primary carbide and containing 30% or more of carbide, it is manufactured and used only by the growth welding method. This is because the eutectic high chromium-based alloy is not suitable to be manufactured as a cast due to the risk of cracking during casting or poor impact toughness. The high masonry high chromium-based alloy, which is manufactured and used only by the growth welding method, is used to form a coating layer from several mm in thickness to several cm by welding on a base material of mild steel having excellent impact toughness. At this time, since the coating layer of the eutectic high chromium carbide-based alloy is combined with the base material of the mild steel, there is no risk of damage.

However, in the case of high chromium carbide-based alloys welded and welded up to now, they have been used as they are only welded on the base material of mild steel or alloy, and thus there is a limit in scratch wear resistance.

Thus, the present inventors conducted research and experiments to improve the scratch wear resistance of the high chromium carbide alloys subjected to conventional overgrowth welding as described above, and the present invention was proposed based on the results. An object of the present invention is to provide a method for producing a high chromium carbide-based growth weld alloy for improving scratch resistance by controlling the microstructure by appropriately controlling the composition of the carbide-based growth weld alloy and heat treatment conditions thereof.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention provides a method for producing a high chromium carbide based weld weld alloy having excellent scratch resistance, and is C: 2.0-6.5%, Cr: 15-35%, Mn: 0.1-5%, and Si: 0.1-2 by weight. %, Single or composite Nb, Mo, W and Ni: 0-15%, the rest: Fe and other inevitable growth in the temperature range of 900-1100 ℃ after the growth welding material to the base material It relates to a method for producing a high chromium carbide-based growth weld alloy excellent in scratch resistance and wear resistance comprising a heat treatment for 1-10 hours.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In order to achieve the above object, in the present invention, it is preferable to first make the growth welding material to be composed of the alloy component system as described above.

C is an iron strengthening element that increases the hardness of the material. In the present invention, it binds with chromium to form a hard primary chromium carbide, and the remainder is dissolved in the austenite structure. Therefore, the carbon content in the present invention should be at least 2.0% capable of forming chromium carbides which contributes to the wear resistance, and when added at 6.5% or more, the brittleness of the present invention becomes poor and rather inhibits wear resistance. Since the lower limit of the addition amount is 2.0%, the upper limit is preferably limited to 6.5%.

Cr is an essential element in the present invention. Coupling with carbon and iron forms hard carbides having low cost and excellent wear resistance, and improving oxidation resistance. In order to form a large number of chromium-based carbides during the heat treatment, more than 15% of the chromium carbide should be added. Since the effect of improving the wear resistance is not obvious and economical at the same time, the lower limit of the added amount is preferably 15% and the upper limit of 35%. .

Mn greatly affects the process reaction depending on the addition ratio with silicon in the present invention. And when it is dissolved, the function of removing dissolved oxygen in molten steel is less than 0.1%, its function is weak, and when it is added more than 6%, it lowers the hardness of austenite phase and eventually causes the disadvantage of inhibiting abrasion resistance. Is preferably 0.1% and the upper limit thereof is limited to 6%.

Si has a function of deoxidizing oxygen in molten steel in the present invention. When 0.1% or less is added, its function is weak, and when 2% or more is added, the present invention causes a perlite phase that impairs brittleness and abrasion resistance, so the lower limit of the added amount is preferably limited to 0.1% and the upper limit to 2%. .

Nb, Mo, and W combine with carbon to form carbides, and Ni imparts toughness and heat resistance. However, since these elements are expensive, the effect of addition is not clear compared to the degree of price increase depending on the amount added. Therefore, it is not necessary to add it, and since it has some effects, it is preferable to limit the lower limit of the added amount to 0% and the upper limit to 15%, in which the added effect becomes insignificant compared to the degree of price increase according to the added amount.

On the other hand, in the present invention, after the steel is formed in the above range, it is grown in a base material and then heat treated at a temperature range of 900-1100 ° C. for 1-10 hours to form chromium that is dissolved in the matrix structure surrounding the carbide. The carbon is bonded to each other to precipitate secondary carbides, and air-cooled to transform all or part of the matrix into martensite to improve scratch wear resistance. The reason is as follows.

In the growth welding process, a part of the base material is melted by arc heat, and a welding electrode material made of a high chromium carbide-based alloy component is melted and fused onto the base material. At this time, the fused molten metal is quenched very quickly (heating rate of 10 ³ ° C / sec) as heat is released into the base metal and the surrounding air, so that some chromium and carbon alloys cannot be sufficiently precipitated, and the base (austenite or pearlite phase) Supersaturated is employed. The chromium and carbon elements supersaturated in the base structure immediately after welding are bonded to each other when the growth welding material is kept at a high temperature for a long time to precipitate as a stable chromium carbide. And the matrix structure in which the supersaturated chromium and carbon components are precipitated as chromium carbides has a martensite transformation point temperature higher than room temperature, and as a result, part or all of the matrix structure is transformed into martensite phase during cooling.

Therefore, the matrix structure surrounding the carbide immediately after the growth welding undergoes a heat treatment process to transform into a high hardness martensite phase in which fine secondary carbides, which may contribute to improved wear resistance, are deposited. At this time, in order to precipitate the secondary carbide during the heat treatment, sufficient thermal conditions should be provided by maintaining the temperature in the temperature range of 900-1,100 ° C for 1-10 hours. At temperatures below 900 ° C., secondary carbides take too long to precipitate, and a holding time of 10 hours or more is no more pronounced secondary carbide precipitation effect and at the same time uneconomical. And the temperature of 1100 ℃ or more is uneconomical because the decarburization reaction is severe on the surface of the growth layer, the surface hardness is lowered and the risk of lowering the wear resistance and heat treatment in an inert atmosphere to prevent this. Therefore, the heat treatment process is preferably maintained for 1-10 hours in the temperature range of 900-1,100 ℃ to sufficiently precipitate the high hardness chromium carbide-type secondary carbide and then transform the matrix structure to high hardness martensite phase while air-cooled to room temperature.

Hereinafter, the present invention will be described in more detail with reference to Examples.

EXAMPLE

30 volts of the growth welding material (flux cored wire having an outer diameter of 3.2 mm) of the comparative material (1, 2) and the invention material (1-7) formed on the base material of mild steel (SS41 steel) having a thickness of 9 mm as shown in Table 1 below. The welding bead was welded in two layers so that the weld bead width was 50 mm and the thickness of one growth layer was 5 mm under 400 amp welding conditions.

The comparative materials (1, 2) and the inventive material (1-6) welded and raised as described above were maintained at 1000 ° C. for 4 hours, and then air-cooled. The comparative material (3) made the invention material (6) at 890 ° C. for 1 hour. After maintaining for a while and then heat-treating under conditions of air cooling, the hardness and the amount of wear before and after the heat treatment were measured and the results are shown in Table 2 below.

At this time, the hardness value of each sample was measured using the Vickers hardness tester. In addition, wear measurement was performed under the same conditions of load: 20kg, wear distance: 4300m, rotation speed: 200RPM, sand diameter: 0.15-0.3mm in a low stress dry sand abrasive test (ASTM Standard G65-85). The amount of wear at the time of the test is shown.

TABLE 1

TABLE 2

As can be seen in Table 2, in the case of the comparative material (1-3) in which the alloy composition does not satisfy the scope of the present invention, the hardness value was rather lowered and the amount of wear was also increased, resulting in the heat treatment inhibiting wear resistance. Brought it. However, all of the invention materials (1-6) satisfying the scope of the present invention by the heat treatment showed a sharp increase in hardness value and at the same time a reduction in wear. In addition, the invention material (7) to which Nb was added also showed excellent hardness value and wear characteristics. Therefore, it can be seen that the heat treatment process has an excellent effect of increasing the hardness and wear resistance of the high chromium carbide based welding material.

As described above, the present invention has the effect of producing a growth welding alloy by controlling the alloying components and by producing a high temperature heat treatment under the appropriate conditions it can produce a growth welding product excellent scratch resistance.

Claims (2)

In the method for producing a high chromium carbide based weld weld alloy having excellent scratch resistance, C: 2.0-6.5%, Cr: 15-35%, Mn: 0.1-6%, Si: 0.1-2%, Residual: High chromium carbide with excellent scratch wear resistance, which includes heating and welding a growth welding material composed of Fe and other inevitable impurities to a base material, and then heat-treating for 1-10 hours at a temperature range of 900-1100 ° C. Method for Producing Cultivated Welding Alloy. In the method for producing a high chromium carbide based weld weld alloy having excellent scratch resistance, C: 2.0-6.5%, Cr: 15-35%, Mn: 0.1-6%, Si: 0.1-2%, Nb, Mo, W, and Ni: 15% or less, remaining: Fe, and a growth welding material composed of other unavoidably contained impurities were grown and welded to the base material, and then 1-10 at a temperature of 900-1100 ° C. A method for producing a high chromium carbide based growth weld alloy having excellent scratch wear resistance, including heat treatment for a time.