KR960000413B1 - Flux cored wire - Google Patents

Abstract

The flux cored wire is produced by filling a filler in a mid steel strip. The filler is produced by mixing ferrochrome of 50-60 wt.%, ferrosilicon of 10-16 wt.%, ferromanganese(high carbon) of 12-18 wt.%, ferromolybdenium of 10-16 wt.%, ferroniobium of 0.1-0.5 wt.%, ferroboron of 8-15 wt.%, calcium carbonate of 4-7 wt.%, fluorite of 2-5 wt.%, rutile of 2-4 wt.%, graphite of 1-3 wt.%, mica of 0.5-1 wt.%, and sintering the mixture.

Description

Flux Cored Wire and Welded Metal for Surface Hardening Welding

1 is a flux cored wire manufacturing process diagram.

2 is a flux cored wire manufacturing line.

3 is a sectional view of a welded part of the grinding mill roller for coal crushing.

4 is a cross-sectional view taken along the line A-A of FIG. 3, showing the hardness measurement position of the weld weld metal.

FIG. 5 shows the microstructure of the deposited metal.

The present invention relates to a flux cored wire used for surface cultivation of coal pulverizing mill rollers and a bowl or wegment, and furthermore, the wires are used for grinding rollers and the like. The present invention relates to a weld metal produced by wet welding.

Surface hardening welding means wear parts that are limited to long-term use on the surface of parts that have been exposed to impact and friction for a long time, such as grinding rollers, railway rails and rolling mills. Is a welding method for uniform welding (growth welding) and regeneration with a welding material of an alloy having abrasion resistance, heat resistance, or corrosion resistance, and this welding method is widely used for improving the surface performance and extending the life of the device.

Therefore, the welding rod used for the surface hardening welding should be selected and used according to the material, purpose of use, welding conditions, etc. of the welded object, so selecting an appropriate welding rod is a major requirement that determines the performance and life of the welded object. . There are various kinds of electrodes, but for surface hardening, so-called flux cored wires, which are formed by filling flux into a mild steel strip, are mainly used. There are various types of flux cored wires according to their composition and shape, and the general manufacturing process is made of U-shaped tubes made of thin strips (0.2 ~ 0.6mm) of 13mm to 16mm width as shown in FIG. It was roll-molded by filling flux and metal powder in the inside. The weight ratio of filled flux to total wire weight is approximately 40-50%.

The manufacturing process line for this is shown in FIG. The positive raw materials used for the positive cored wire are usually the arc stabilizer which stabilizes the arc, the gas former which blocks the molten metal from the atmosphere so that oxidation and nitriding reactions do not occur, and desulfurization and deoxidation by appropriate metallurgy reactions. It is made of a mixture of deoxidizer and slag forming agent to make a beautiful appearance by improving the fluidity of slag and slag, and the alloying component required for the weld metal.

In particular, metal-cored wires for self-shielding g-flux cored arc welding (SS-FCAW) for surface hardening are applied to the grinding rollers for coal and cement mills, pressure vessels and piping of power plants, which are subject to extreme wear. Metal Cored Wire) is used.

As shown in Table 1, the electrode consists of a large amount of chromium and carbon, and V, W, Mo, etc. are added to improve abrasion resistance through carbide precipitation, and Mn, Si, etc. are added to improve weldability, and arc is added. Oxides and minerals are added that play a role in stabilization and slag formation.

In the case of welding with a surface hardening welding rod, that is, a high chromium iron-based welding material having increased contents of chromium and carbon, it is true that a large amount of chromium carbide is deposited on the fused metal, thereby making a significant contribution to improving the hardness. Table 2 shows the components of the deposited metal.

However, when welding to precipitate chromium carbide (Cr-Carbide) with the conventional flux-cored wire, the carbide is dissolved evenly by arc heat during welding, and the carbide is not evenly distributed on the weld metal, and the chromium carbide is coarse at the grain boundaries in the weld metal. Since the precipitation is mainly focused on the grain boundary where carbides are collected, the hardness is high but the toughness of the metal is weak, and the performance of the roller or the rotating plate of the coal mill for grinding is poor and the life is short.

In order to solve this problem, a study has been attempted to precipitate niobium and boron carbides in addition to chromium carbide by adding niobium (Nb) or boron (B).

Therefore, the inventors have recognized that the impact toughness improvement of the weld metal is most important for this material because it is caused by cracks as the main wear factor of the high chromium growing layer. As a result of many years of research, a certain amount of boron (B) and a small amount By adding niobium (Nb) to the existing flux cored wire, the grain boundary corrosion caused by chromium-carbide precipitates is reduced, and the carbide produced is refined and homogenized to improve wear resistance and toughness, and to enable multilayer welding with a thickness of 60 mm or more. It succeeded in improving the use time of the deposit by 2.0 ~ 2.5 times or more. The flux cored wire composition of the present invention is shown in Table 3.

The main object of the present invention is to provide a flux cored wire suitable for the growth welding of coal mill grinding rollers and rotary plates, and another object of the present invention is to provide a weld metal welded to the rollers and rotary plates of grinding mills.

According to a first aspect of the present invention, the present invention is a flux cored wire made by filling a filler in a mild steel strip, wherein the filler is ferrochrome 50-60 Wt%, ferrosi silicon 10-16 Wt%, Ferro Manganese (High Carbon) 12-18Wt%, Ferro Molybdenum 10-16Wt%, Ferroniobium 0.1-0.5Wt%, Ferroboron 8-15Wt%, Calcium Carbonate 4-7Wt%, Fluorite 2-5Wt%, Geum Heungseok 2- A flux-cored wire for surface hardening welding is characterized by mixing and sintering 4 Wt%, graphite 1-3 Wt% and mica 0.5-1 Wt%.

According to a second aspect of the present invention, the present invention provides C: 4-6Wt%, Si: 1.5-3.5Wt%, Mn: 3-5Wt%, Cr: 15-25Wt%, Mo: 4-7Wt%, B: 0.5 -2.0 Wt%, Nb: 0.02-0.30 Wt%, providing a deposited metal formed by surface hardening welding consisting of the remaining Fe.

Hereinafter, the manufacturing process of the flux cored wire of the present invention will be briefly described.

The flux cored wire is 50-60Wt% ferrochrome, 10-16Wt% ferrosilicone, 12-18Wt% ferro-manganese (high carbon), 10-16Wt% ferro-molybdenum, ferro niobium 0.1-0.5Wt%, ferroboron 8-15Wt%, calcium carbonate 4-7Wt%, formed 2-5Wt%, Geum Heungseok 2-4Wt%, graphite 1-3Wt%, mica 0.5-1Wt% It is filled into the inside of the base and molded into a certain shape.

Hereinafter, the reason which limited the numerical value of each filler of this invention welding wire is demonstrated.

Ferro chromium is an important component that causes chromium-carbide precipitation to improve abrasion resistance, but it is difficult to obtain a predetermined hardness at 50 Wt% or less. Cr-rich carbides at 60 Wt% or more are very rapidly coarse at high temperatures. It is dislodged and has a light ferrite, resulting in poor wear resistance.

Ferro silicon and ferro manganese (high carbon) are used to prevent deoxidation of weld metals as well as to contain impurities, and at higher than 16 Wt% of ferro silicon and above 18 Wt% of ferro manganese, overdeoxidation and grains cause coarsening and corrosion resistance. In the case of less than 10 Wt% of silicon and less than 12 Wt% of manganese, it is not possible to obtain a healthy weld metal due to the lack of deoxidation.

Ferro molybdenum improves corrosion resistance and abrasion resistance, with an emphasis on preventing high temperature embrittlement by adding 10-16Wt% to improve corrosion resistance and abrasion resistance or to prevent brittleness at high temperatures.

Ferro niobium is a deoxidizer that replaces silicon (Si) and manganese (Mn), and forms insoluble niobium (Nb) carbide to reduce grain boundary corrosion by precipitation of Cr carbide. At the same time, the wear resistance decreases and the metal plays an important role as a heat-resistant alloy of intermetallic compounds, but embrittlement phenomenon occurs due to grain boundary precipitation. When 0.1 Wt% or less is added, it is difficult to obtain a predetermined effect due to the addition of Nb.

Feroborone is a chemically stable material with carbon at a high temperature of 2500 ° C, which favors heat treatment conditions such as improved hardenability and combines with nitrogen to increase wear resistance and corrosion resistance. Feoro boron is less than 8Wt%, weak bonding force with nitrogen and less quenching, wear resistance, corrosion resistance is reduced, if more than 15Wt% toughness is the cause of cracking.

Calcium carbonate stabilizes the arc to suppress blow hole and spatter generation to the maximum, thereby making it stable in workability, but worsening the stability of the arc above 7.0 Wt%, and below 4.0 Wt% (Shielding gas) is insufficient and oxygen and nitrogen in the air invade into the weld metal, and as a result, they remain as impurities to obtain a healthy weld metal.

Fluorite is effective for refining molten steel and improving molten metal fluidity. At 2Wt% or less, refining of the molten steel is unreliable, and at 5Wt% or more, beads are poor.

Rutile Sand contributes to slag fluidity and arc stability, and when slag flow is lower than 2.0Wt%, the slag flow becomes unstable, and when it is above 4.0Wt%, slag peeling is difficult.

Graphite is added to increase the arc stability and carbon in the fused metal. To obtain 4-6 Wt% carbon to the deposited metal, 1-3Wt% was added.

When 0.5-1Wt% is added and the mica is less than 0.5Wt%, the arc is unstable, and when it is 1Wt% or more, slag fluidity is deteriorated, so slag peeling is difficult and the appearance of beads becomes worse.

In order to test the efficacy of the flux cored wire of the present invention, the inventors made six samples shown in Table 4, and performed multilayer welding on the grinding mill roller for coal grinding of FIG. As a result, a, b, c was capable of multi-layer welding up to 60 mm, but d, e, f had a risk of breaking the roller due to rapid propagation of cracks at 25-30 mm.

3 is a sectional view of the coal grinding mill, in which the reference numeral 21 denotes the inner space of the roller, 23 denotes the base material of the roller, and 25 denotes a weld metal.

4 is a position chart of the hardness measurement of the raised weld metal, and reference numeral 1-10 denotes a hardness measurement site.

As a result, samples a, b and c of the present invention were capable of multi-layer welding with a thickness of 60 mm or more. This was impossible.

Table 5 shows the components of the weld metal that has been welded by the wires of samples a, b and c. d, e, and f show the fused metal component at the time of 30 mm wet welding.

Table 6 shows the hardness values of the welded metal section welded and welded with the wires of sample a-f. Here, it can be seen that the hardness values of a, b, and c welded by the present invention are excellent.

Table 7 shows the amount of wear when the grinding mill roller welded by the outer wire of Samples a-f was used under the same conditions.

Table 8 shows the fused metal toughness test results of Samples a-f.

Table 9 shows the chemical composition of the raw material for filling perlux.

Table 10 shows the mild steel components.

TABLE 1

TABLE 2

TABLE 3

TABLE 4

TABLE 5

TABLE 6

TABLE 7

O. Okoshi type abrasive wear test

-Sliding speed: 1.37m / sec

-Slide length: 600m

Final load: 3.2kg

Rotating disk: ø30. h 3 mm (SCM 440)

TABLE 8

TABLE 9

TABLE 10

As a result of the test, it was confirmed that the weld metal welded by using the flux cored wire of the composition had excellent wear resistance and toughness, which greatly increased the life and performance of the product than the conventional one. In addition, it is possible to weld a multi-layered welding with a thickness of 60 mm or more, and it can be seen that it has an excellent effect not only for grinding but also for curing growth of rolls and piston rings of rolling mills.

Claims (3)

In a flux cored wire filled with a filler inside a mild steel strip, the filler is ferrochrome 50-60 Wt%, ferro silicon 10-16 Wt%, ferro manganese (high carbon) 12-18 Wt%, ferro Molybdenum 10-16Wt%, Ferroniobium 0.1-0.5Wt%, Ferroboron 8-15Wt%, Calcium Carbonate 4-7Wt%, Fluorite 2-5Wt%, Gelatin 2-4Wt%, Graphite 1-3Wt%, Mica 0.5- A flux cored wire for surface hardening welding, characterized by mixing and sintering 1 Wt%. C: 4-6Wt%, Si: 1.5-3.5Wt%, Mn: 3-5Wt%, Cr: 15-25Wt%, Mo: 4-7Wt%, B: 0.5-2.0Wt%, Nb: 0.02-0.30Wt %, Weld metal formed by surface hardening welding consisting of the remaining Fe. The weld metal according to claim 2, wherein the weld metal is formed by a flux cored wire for surface hardening welding according to claim 1.