JPH0418125A - Production of metal fiber for reinforcement of refractory - Google Patents

Abstract

PURPOSE:To obtain the subject fiber having increased strength at normal temperature and useful for embedding in a high-alumina castable refractory to prevent the collapse of the refractory by forming an alloyed steel containing chromium and aluminum in the form of a wire, etc., and hardening the wire by cold working. CONSTITUTION:An alloyed steel composed of 10-27% chromium, 1-7% aluminum and the remaining amount of iron and inevitable impurities (e.g. carbon and silicon) is rolled to form a wire or ribbon, which is subjected to cold working and then press-forming, etc., to obtain the objective fiber.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is aimed at preventing the collapse of high-alumina monolithic refractories used in high-temperature applications in steel manufacturing by embedding them in the refractories. The present invention relates to a method for manufacturing the metal fiber used.

[Issues with conventional technology]

Traditionally, the materials of metal fibers used to prevent the collapse of monolithic refractories have been soft steel for medium-temperature applications, various types of stainless steel, and NK? for high-temperature applications. 250. -2O
It was made of N4 heat-resistant steel. Products manufactured from these materials exhibit sufficient heat resistance in medium temperature ranges such as forging or rolling heating furnaces, and high temperature ranges such as homogenization heating furnaces for steel ingots and slabs. However, long-term contact with molten steel,
The above-mentioned conventional method is used for ultra-high temperature applications such as tamp tubes and lids for continuous casting that receive radiant heat from 7-volume steel in a nearby furrow or receive high-temperature radiant heat during smelting of molten steel, and immersion tubes used in degassing scouring systems. Even alloy steels still lack oxidation resistance,
Its lifespan was limited to about 40 tappings.

For this reason, there has been a demand for a PL with excellent oxidation resistance and low material cost.

Furthermore, conventional metal fibers do not have sufficient bonding strength with high-alumina monolithic refractories for high-temperature applications, which hastened their collapse.

Furthermore, conventional metal fibers are flexible when they have a small diameter, so when they are kneaded into refractories, the metal fibers tend to clump together and are not evenly dispersed in the refractories. This creates areas in the refractory where no metal fibers exist, resulting in a significant decrease in strength.

For this reason, it is necessary to use a wire with a considerably large diameter, which raises the problem of increased material costs.

[Means to accomplish the task]

Therefore, the present invention seeks to provide a method for producing metal fibers for reinforcing refractories that can address the above-mentioned problems. In order to achieve that purpose, the present invention uses 10 to 10% of chromium.
27% aluminum, and 1 to 7% aluminum is made into a wire or band shape, and then the material is subjected to further cold working to increase the strength at room temperature through work hardening. This is a method for producing metal fibers for reinforcing refractories to be embedded in shaped refractories.

〔Example〕

The alloy steel used in this example contains 16% chromium.

Contains 2% aluminum, with the remainder consisting of iron and unavoidable impurities. This unavoidable impurity includes carbon 0.1
5% or less, silicon 0501-2.0%, manganese 0,0
1 to 1.5%, nickel 0.02% to 2.0%, etc.

In this alloy steel, the chromium content must be in the range of 10 to 27%, since oxidation resistance is improved when the chromium content is 10% or more, and cold workability becomes extremely poor when the chromium content exceeds 27%. Furthermore, by adding aluminum to this, oxidation resistance is significantly improved. This is thought to be due to the fact that an aluminum oxide film is deposited on the surface layer of the alloy, which protects the base metal from oxidation. At the same time, this aluminum oxide film combines with alumina contained in refractories for high-temperature applications at high temperatures, and as a result, the metal fibers chemically bond with alumina through the aluminum oxide film. Therefore, even if a crack occurs in the refractory, the fibers will not come out, which is thought to prevent the refractory from collapsing. Such an effect can be seen from an aluminum content of 1%, and it is usually sufficient to include 2% or more, but if it exceeds 7%, it is not only uneconomical because the cost of raw materials increases, but also reduces the amount of aluminum oxide generated. The aluminum content should be in the range of 1 to 7%, since the aluminum content would be excessively high and the hard coating would cause significant roll wear during rolling.

In addition, this alloy steel contains 0.1 to 0.6% titanium and 0 niobium.
,01-0.5%, Poron 0.002-0.015%,
By adding one or more of 0.005 to 0.1% of other rare earth elements, the grain size of this alloy steel can be adjusted and the workability can be improved. However, these additive ingredients have no effect below the above lower limit,
Furthermore, if the upper limit is exceeded, the workability will be deteriorated and the precipitation of aluminum oxide will be hindered, so the above additive components must be within the above range.

However, in the method for producing metal fibers for reinforcing refractories according to the present invention, alloy steel having the above composition is first rolled into a wire or strip shape, and then the wire or strip material is further cold-worked to form the material. The room temperature strength is increased by work hardening. In addition, wire rods are cold-worked to form a round cross-sectional shaft shape as shown in Fig. 1, or belt-shaped materials are cold-worked to form an angular cross-section shaft shape as shown in Fig. 2. Alternatively, press processing may be further added to that shown in FIG. 1 to form a metal fiber having a shaft diameter varying in size at a constant pitch, as illustrated in FIG. 3.

Alternatively, the wire can be bent into a waveform of equal pitch and width as shown in Fig. 4, a rectangular waveform as shown in Fig. 5, or an unequal pitch waveform as shown in Fig. 6. is the seventh
Metal fibers of various shapes can be manufactured by bending the fiber into a waveform of unequal pitch or unequal width as shown in the figure, and cutting it to a fixed size.

The metal fibers produced in this way have increased rigidity due to work hardening compared to those produced without cold working. Therefore, when kneaded into a refractory, the metal fibers are well dispersed without clumping together into lumps. The high-alumina monolithic refractories kneaded with metal fibers are solidified and constructed into ultra-high temperature structures such as furnace walls or converter tundishes. At this time, the metal fibers are buried in the refractory in a three-dimensional entwined state in a net shape, and the intertwined structure increases the mechanical strength of the refractory.

Note that the cross-sectional shape of the wire is not only circular but also oval.

It may be rectangular or the like, and in that case, the wire diameter should be 0.1 to 1n+ in short diameter or thickness and 0.2 to 2 in long diameter or width to improve economic efficiency.
Cranes, 10 to 80 orchid in length, and the pitch of the waveform is 2
~6fi was practically effective.

In addition, when cutting the wire rod, the mechanical bond with the refractory becomes stronger by making the wire rod have burrs, burrs, slight bends, and twists, and by creating a shape that is a combination of these. This makes it difficult for fibers to come out even if cracks form in the refractory.

When the metal fibers produced in this way were mixed into a high alumina monolithic refractory and used as a tandem refractory for a converter, the lifespan was approximately 1.5 times longer than that of conventional materials. That is, the life of the conventional converter tundish was about 40 times, but when the metal fiber of the present invention was mixed, the life was extended to 60 times.

Table 1 shows the chemical compositions of conventionally used mild steels, various chromium steels, various stainless steels, and the alloy steel of the present invention, each of which was embedded in a high alumina monolithic refractory and heated at 1250°C.
The oxidation depth after heating is shown in 00 JP-A.

Generally, the bond strength between a refractory and a metal depends on the strength of the metal oxide coating and the boundary strength between the coating and the refractory. The thicker the metal oxide film, the stronger the boundary strength with the refractory, but the strength of the oxide film itself decreases, making the refractory more likely to collapse.

As in the present invention, the alloy steel containing ~7% aluminum deposits an aluminum oxide film on the surface, which chemically bonds with alumina in the high alumina monolithic refractory and forms a bond with the refractory. increases the boundary strength of As a result, the aluminum oxide film can be made thinner and the bonding strength can be improved.

〔Effect of the invention〕

As explained in the examples above, the metal fiber for reinforcing refractories of the present invention significantly improves oxidation resistance by containing predetermined amounts of chromium and aluminum. By embedding the alumina in the metal fiber, the alumina is chemically and firmly bonded to the thin and strong aluminum oxide coating deposited from the metal fiber. Therefore, due to the combined effect of its strong bond and oxidation resistance, separation from the refractory is suppressed and the structure can be strongly reinforced. However, since the metal fibers are manufactured by subjecting the material to cold working, the rigidity increases through processing and hardening, and even if the wire diameter is small or the thickness of the plate is thin, it will not harden and be uniformly dispersed in the refractory. It has beneficial effects such as ease of use.

[Brief explanation of the drawing]

The drawings show metal fibers for reinforcing refractories according to the present invention, and FIGS. 1 to 3 are perspective views of straight rod-shaped metal fibers, and FIGS. 4 to 7 are perspective views of corrugated metal fibers. Figure 1 Figure 2 Figure 8 Figure 4 Figure 5-4, 4. , 4-I B Figure 7

Claims (1)

[Claims] High alumina, which is characterized by making alloy steel containing 10 to 27% chromium and 1 to 7% aluminum into a wire or band shape, and then cold working the material to increase its strength at room temperature through work hardening. Method for producing metal fiber for reinforcing refractories to be embedded in monolithic refractories