JP2004238276A - Method for producing high carbon ferrochrome air granulated slag and grinding material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new method for producing high carbon ferrochrome air granulated slag. <P>SOLUTION: High carbon ferrochrome molten slag comprising 6 mass% or less of Cr<SB>2</SB>O<SB>3</SB>, 20-40 mass% of MgO, 20-40 mass% of Al<SB>2</SB>O<SB>3</SB>, 25-45 mass% of SiO<SB>2</SB>, and 1-5 mass% of CaO at a temperature of 1,300-1,450°C is air-granulated using a main nozzle for air granulation and an upper nozzle for preventing scattering provided above the main nozzle for air granulation to produce spherical high carbon ferrochrome air granulated slag with a particle size of 0.1-5.0 mm. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  A method and a method for manufacturing a high-carbon ferrochrome-blasted slag that can spray and pulverize molten slag flowing out of a high-carbon ferrochrome molten slag outflow gutter by air jetted from a nozzle to stably produce a high-quality blown slag with a high yield. Regarding cleaning materials.

  Prior to painting the surface of ships, bridges, oil tanks, castings, etc., blasting is performed. A general blasting method using a blasting machine is a method in which abrasive material such as steel or fine silica sand is sprayed onto the surface of a steel material by high-pressure air using a nozzle. The abrasive material blown out together with the air strongly collides with the target object, and removes dirt and an oxide film on the surface. As a result, a normal active surface is obtained on the surface of the target object.

  Conventionally, a steelmaking slag is used as the conventional crushed slag. The milled slag of this steelmaking slag had a problem that CaO content was high, easily broken, changed with time, and had low strength.

  A technique using a molten slag having a low CaO content generated during ferrochrome refining as a polishing material instead of steelmaking slag is disclosed.

  For example, Patent Document 1 (JP-A-56-9168) discloses an abrasive for blasting high-carbon ferrochrome slag having a particle size of 0.5 to 5.0 mm.

  Patent Document 2 (Japanese Patent Application Laid-Open No. Hei 9-109030) discloses that molten slag generated during ferrochrome refining is atomized with a supersonic gas of Mach 1 or more to obtain a granular material having a particle size of 0.2 to 2.5 mm. A method for producing an abrasive material is disclosed.

JP-A-56-9168 JP-A-9-109030

  However, the abrasive material for blasting described in Patent Document 1 is crushed slag and is expensive. Furthermore, the surface roughness cannot be obtained as a material to be polished, and the material to be polished is put on the surface to be polished.

  In the method for manufacturing a polishing material described in Patent Document 2, since the air is pulverized by a main single-stage nozzle that jets out a supersonic gas of Mach 1 or more, a portion of the falling molten slag that is not sprayed is removed. , And scatters on the upper side or the main first-stage nozzle side, and the yield is low. In addition, there are side nozzles on both sides of the main nozzle, which requires a large amount of air.

  An object of the present invention is to provide a new method for producing high-carbon ferrochrome crushed slag and an abrasive material produced by the method.

In order to solve the above-mentioned problem, the invention according to claim 1 includes a component Cr ₂ O ₃ : 6% by mass or less, MgO: 20 to 40% by mass, Al ₂ O ₃ : 20 to 40% by mass, SiO ₂ : High-carbon ferrochrome molten slag having a temperature of 1300 to 1650 ° C. at 25 to 45% by mass and CaO: 1 to 5% by mass using a main nozzle for air blasting and an upper nozzle for preventing scattering provided above the main nozzle for air blasting. It is characterized in that it is pulverized to produce a spherical high-carbon ferrochrome pulverized slag having a particle size of 0.1 to 5.0 mm.

  High carbon ferrochrome molten slag has a higher viscosity than steelmaking slag. For this reason, when the high carbon ferrochrome molten slag is to be pulverized, it is necessary to increase the flow velocity of the air ejected from the main nozzle for the pulverization to about the sonic speed or more. According to the present invention, since the upper nozzle for scattering prevention is provided in the upper direction of the main nozzle for wind breaking, first, the upper nozzle for scattering prevention changes the falling direction of the molten slag forward, and then, The main nozzle sprays and pulverizes the slag that has changed direction. For this reason, even if the flow velocity of the air ejected from the main nozzle for wind crushing is high, it is possible to suppress the flow of the molten slag to the side of the main nozzle for wind crushing.

According to a second aspect of the present invention, in the method for producing a high carbon ferrochrome crushed slag according to the first aspect, the main nozzle for blasting is a Laval nozzle, the wind speed is 340 m / sec or more, and the atomizing ratio (Nm ³⁾ / Min / slag kg / min) is 0.10 or more, and the wind speed of the upper nozzle for scattering prevention is 10 to 200 m / sec.

The slag that has landed or collides with the hood immediately after the blasting when the development of the solidified layer is insufficient becomes a flat slag. This phenomenon is related to the (air / slag) ratio. When the atomization ratio (Nm ³ / min / slag kg / min) is 0.10 or more, almost all spherical slag can be obtained. In addition, the slag particle size changes depending on the air velocity, and the higher the air speed, the smaller the average particle size tends to be. In order to reduce the particle size of the high-carbon ferrochrome slag having a high melting point and a high viscosity, and to collect it with good yield, the wind speed of the main nozzle exceeds 340 m / sec.

  According to a third aspect of the present invention, in the method for producing high-carbon ferrochrome slag according to the first or second aspect, the temperature is set to 1500 to 1650 ° C.

  The molten slag of high carbon ferrochrome tends to have a higher viscosity at lower temperatures. According to the third aspect of the present invention, the viscosity of the molten slag is reduced by air-blasting at a high temperature, and a small-diameter air-blasted slag can be obtained.

The invention according to claim 4, components Cr ₂ O _3: 6 wt% or less, MgO: 31 to 37 wt%, Al ₂ O _3: 23~31 wt%, SiO _2: 30 to 37 wt%, CaO:. 1 to High-carbon ferrochrome for producing 5% by mass, high-carbon ferrochrome molten slag having a mass ratio of SiO ₂ / MgO of 0.95 or more to produce spherical high-carbon ferrochrome slag having a particle size of 0.1 to 5.0 mm. This is a method for producing air-crushed slag.

When the mass ratio of SiO ₂ / MgO is 0.95 or more, the flowability of the molten slag is improved, and the yield of the air-milled slag is improved. In addition, cracking of the air-blasted slag during cleaning is reduced.

  According to a fifth aspect of the present invention, in the method for producing a high carbon ferrochrome blast slag according to the fourth aspect, the high carbon ferrochrome molten slag is prevented from being scattered provided above the main nozzle for the blast and the main nozzle for the blast. It is characterized in that it is crushed by using an upper nozzle.

  The invention of claim 6 is an abrasive material produced by the method for producing high-carbon ferrochrome slag according to any one of claims 1 to 5.

  Hereinafter, embodiments of the present invention will be described. FIG. 1 shows a manufacturing apparatus used in carrying out a method for manufacturing a crushed slag. The molten slag is transferred from slag pan 1 to tundish 2. Immediately below the tundish 2, a main nozzle 3 for air crushing (hereinafter simply referred to as a main nozzle) and an upper nozzle 4 for scattering prevention (hereinafter simply referred to as an upper nozzle) are arranged to face the falling flow of the molten slag. The upper nozzle 4 and the main nozzle 3 are arranged vertically, and the upper nozzle 4 is arranged above the main nozzle 3. The high-carbon ferrochrome molten slag is sprayed and pulverized (that is, air-crushed) by air jetted from the upper nozzle 4 and the main nozzle 3 to obtain an air-crushed slag having a particle size of 0.1 to 5 mm.

  In the present embodiment, a molten slag which is produced as a byproduct when high carbon ferrochrome is produced in an electric furnace is used as a raw material.

(component)
CaO: If CaO content is present, the strength is reduced, and the material becomes brittle and easily powdered.

Cr ₂ O ₃ : Cr ₂ O ₃ is 6.0% by mass or less to prevent elution of Cr.

Other, maintain liquidity, hardness, since the toughness ensuring, Al ₂ O _3: 20~40 wt%, MgO: 20 to 40 wt%, SiO _2: a 25-45 mass%.

Here, Al ₂ O _3: 23~31 wt%, MgO: 31 to 37 wt%, SiO _2: 30 to 37 wt% is desirable.

When the mass ratio of MgO / Al ₂ O ₃ increases, the fluidity deteriorates. In addition, the recovery rate of the abrasive material deteriorates. When the mass ratio of MgO / Al ₂ O ₃ decreases, the slag (Cr ₂ O ₃ )% increases, and it cannot be used as an abrasive for environmental protection. For this reason, the mass ratio of MgO / Al ₂ O ₃ is appropriately 1.0 to 1.6. SiO ₂ is set to 30% by mass or more in order to secure the fluidity of the slag. When the mass ratio of SiO ₂ is 37% or more, there is a problem of corrosion of refractories, which is not practical.

The mass ratio of SiO ₂ / MgO is desirably 0.95 or more from the viewpoints of improving the fluidity of the molten slag and the yield of the crushed slag, and suppressing cracking of the crushed slag during polishing.

(temperature)
Hot water is discharged from the electric furnace at 1620 ° C., and its freezing point is 1260 ° C. Therefore, it is crushed between 1300 and 1650 ° C. In order to improve the fine grain yield by securing the fluidity of the molten slag, the temperature is preferably 1500 ° C. or higher.

(E / a value)
The larger the E / a value, the smaller the particle size.

E = (Amount of gas ejected from nozzle (Nm ³ / min)) × (Flow rate of gas ejected from nozzle (Nm ³ / sec)) ²
a = Molten slag flow rate (Ton / Hr)

  Wind speed and air volume are required for particle size control. High carbon ferrochrome molten slag has a high melting point and high viscosity. Therefore, a large atomizing energy is required as in the present invention.

(nozzle)
The slag that has landed or collides with the hood immediately after the blasting when the development of the solidified layer is insufficient becomes a flat slag. This phenomenon is related to the (air / slag) ratio. When the atomization ratio (Nm ³ / min / slag kg / min) is 0.10 or more, almost all spherical slag can be obtained.

  In addition, the slag particle size changes depending on the air velocity, and the higher the air speed, the smaller the average particle size tends to be. In order to reduce the particle size of the high-carbon ferrochrome slag having a high melting point and a high viscosity, and to collect it with good yield, the wind speed of the main nozzle 3 exceeds a sound speed of 340 m / sec. The nozzle is a Laval nozzle.

  The upper nozzle 4 is located above the main nozzle 3 and prevents the backflow of the slag, the rearward slag, and the upper scatter due to the high-speed main nozzle. Since granulation is not performed, the wind speed has an upper limit. The shape is a parallel tube or a tapered nozzle. Further, the air of the upper nozzle 4 also contributes as cooling air during the flight of the blast slag.

  FIG. 2 is a schematic diagram showing the flight of the falling slag by the upper nozzle 4 and the main nozzle 3. First, the upper nozzle 4 changes the falling direction of the molten slag 5 forward. Thereafter, the molten slag 5 whose direction has been changed by the main nozzle 3 is sprayed and pulverized. Since the falling direction of the molten slag 5 is changed, the flow of the molten slag 5 toward the main nozzle 3 can be suppressed. If the upper nozzle 4 is not provided, of the molten slag 5a that falls in the vertical direction, the portion that is not sprayed returns to the main nozzle 3, and the molten slag adheres to the main nozzle 3 and the operation cannot be performed.

  As described above, high-viscosity high-carbon ferrochrome slag can be fine-granulated with high yield by air-blasting with the two-stage nozzle. Of course, a similar effect can be obtained by providing a nozzle in the upper direction of the upper nozzle 4 and air-blasting with a three-stage nozzle.

  In order to prevent the backflow of the molten slag by the upper nozzle 4, the main nozzle 3 can be provided with the inclination angle α, so that the flight time can be maintained. Actually, the inclination angle of the upper nozzle 4 is 5 ° to 10 °, and the inclination angle of the main nozzle 3 is 5 ° to 20 °.

(Physical properties of crushed slag)
Ultra-hardness: Spinel (MgO.Al ₂ O ₃ ) or forsterite (2 (MgO _0.96 .FeO _0.04 ) SiO ₂ ) has a main mineral composition, has high hardness, and becomes ultra-hard when further cooled rapidly.
-Abrasion resistance: Not only hard but also resistant to abrasion and excellent in durability.

  The particles are spheronized by crushing, and those having a diameter of 2.5 mm or less are almost spheroidized. Those having a diameter of 2.0 to 5.0 mm are formed as slightly distorted spheres (sub-spheres), but any of them can be used as spheroidized ferroalloy slag.

(About abrasive material)
The abrasive material of the present invention is used for blasting as a coating base treatment or the like.

  As described above, a general blasting method using a blast machine is a method in which fine particles (abrasive material) of steel or silica sand are blown onto the surface of a target object by high-pressure air using an ejector nozzle. The abrasive material blown out together with the air strongly collides with the object, and removes dirt and an oxide film on the surface thereof. As a result, a clean active surface is obtained on the object.

  It is considered that the abrasive used for the blasting treatment has high hardness and low specific gravity. In other words, those with high hardness have excellent scavenging properties and high scavenging efficiency, and those with low specific gravity hardly cause clogging of the ejector nozzle, and can stably supply the ejector nozzle. Can be easily cleaned.

  Conventionally used abrasive materials include those made of steel such as steel shot, steel grit, cut wire, granulated slag (copper slag, nickel slag, lead slag, etc.) and silica sand.

  However, silica sand has sufficiently high hardness, low specific gravity, and excellent work efficiency.However, when it collides with a target object, it is very easy to be crushed, there is a problem that the working environment is bad, and the specific gravity is slightly too small. Therefore, it is difficult to make the surface of the target object a surface having a roughness of 40 μm or more. For this reason, thick coating paints such as heavy anticorrosion paints that have been frequently used in recent years have a problem that the adhesion of the coating films is poor. Steel shots and other materials made of steel are less likely to be crushed during work and generate less dust. Therefore, the work environment is very good compared to silica sand, but the specific gravity is relatively large, so the air supply is insufficient. Then, there is a problem that it is difficult to be sucked into the ejector and the cleaning efficiency is reduced.

  The reason why the particle size is limited to 0.1 to 5.0 mm is that if the particle size is less than 0.1 mm, the surface roughness of a predetermined value or more necessary for improving the adhesion of the coating film even in a thick coating type paint. On the other hand, if it exceeds 5.0 mm, the suction efficiency of the ejector is reduced, the working efficiency is deteriorated, and the possibility that the ejector is blocked is increased.

  Further, since the crushed spherical slag blast material converts much of the impact energy into impact on the periphery, it can fly a wide range of rust, thereby increasing the blasting ability (that is, the blasting ability).

  Further, the abrasive material of the high carbon ferrochrome crushed slag has a small amount of dust at the time of blasting, so that the working hand can be confirmed in the close striking, the quality of the base adjustment can be easily confirmed, and the safety at the time of working can be secured. A major factor maintaining the superiority with other abrasive materials is that the amount of dust is small due to the low crushing rate during blasting.

  In addition, since it has a uniform roughness, it has excellent paint adhesion.

  Since the shape is spherical, the fluidity is good and the pressure feeding becomes easy. For this reason, the wear of the hoses and nozzles of the polisher is reduced, and the maintenance burden on the machine is reduced.

  Since the air-milled slag exhibits weak alkalinity (pH 8 to 9.5), the polished surface also becomes weakly alkaline and has an anticorrosive effect.

  The air-blasted slag produced by the method for producing high-carbon ferrochrome air-blasted slag of the present invention may be used as a material for a mold, an aggregate for concrete, a cement for mortar, a non-slip floor material, etc. it can.

  A high-carbon ferrochrome molten slag having a tapping temperature of 1620 ° C. was poured from an electric furnace (40000 KVA), flowed through a flow gutter, and air-crushed by a nozzle arranged below the gutter.

  The conditions are shown below.

  The amount of slag was 12 tons in 20 minutes.

Air was sent from the compressor to the Laval-shaped main nozzle, and the air was discharged at an air volume of 111 Nm ³ / min and a wind speed of 512 m / sec.

The upper nozzle sent air from a blower and discharged it at an air volume of 50 Nm ³ / min and a wind speed of 30 m / sec.

  The blasted slag was flown into a wind tunnel having a length of 30 m and a height of 6 m in front of the nozzle, and was collected after cooling.

  The recovered particle size was 94% at 0.1 to 5.0 mm.

  Tables 1 to 3 show the properties of the recovered ferrochrome slag.

  Blasting was performed using the high carbon ferrochrome crushed slag of the present invention, nickel slag, garnet, and silica sand.

  The conditions were as follows.

Blasting condition ・ Compressor pressure: 7kg / cm ²
・ Nozzle tip pressure: 5 kg / cm ²
・ Projection distance: 80cm

Surface to be polished ・ SS material, tar epoxy resin paint

  Table 4 shows the dust amount of the abrasive.

  A major factor in maintaining the superiority with other abrasive materials is that the amount of dust generated is small due to the low crushing rate during blasting.

  The base adjustment rank Sa2Ｓ1 / 2 is maintained.

  The surface roughness measurement of the blast surface by the stylus roughness meter can be said to be sufficient as an underlayer in the range of Rz (same average value) of 75 to 50 μm.

Table 5 compares the amount of dust generated when the mass ratio of SiO ₂ / MgO in the molten slag is 1.06 and 0.84.

It was found that when the mass ratio of SiO ₂ / MgO was 1.06, the cracks of the air-blasted slag during polishing were reduced.

Production equipment used for implementing the method for producing air-crushed slag. The schematic diagram which shows the flight of the falling slag.

Explanation of reference numerals

1. Slag pan 2. Tundish 3. Main nozzle for wind crushing (main nozzle)
4: Upper nozzle for scattering prevention (upper nozzle)
5,5a ... Molten slag

Claims (6)

Components Cr ₂ O _3: 6 wt% or less, MgO: 20 to 40 wt%, Al ₂ O _3: 20~40 wt%, SiO _2: 25 to 45 wt%, CaO: temperature 1300 to 1-5 wt% The 1650 ° C. high carbon ferrochrome molten slag is blasted using a main nozzle for blasting and an upper nozzle for preventing scattering provided above the main nozzle for blasting, and has a spherical height of 0.1 to 5.0 mm in particle diameter. A method for producing high carbon ferrochrome slag which produces carbon ferrochrome slag. The wind breaking main nozzle is a Laval nozzle, the wind speed of which is 340 m / sec or more, the atomizing ratio (Nm ³ / min / slag kg / min) is 0.10 or more, and the wind speed of the scattering prevention upper nozzle is The method for producing a high carbon ferrochrome crushed slag according to claim 1, wherein the slag is 10 to 200 m / sec.   The method for producing a high-carbon ferrochrome-blasted slag according to claim 1 or 2, wherein the temperature is set at 1500 to 1650 ° C. Components Cr ₂ O _3: 6 wt% or less, MgO: 31 to 37 wt%, Al ₂ O _3: 23~31 wt%, SiO _2: 30 to 37 wt%, CaO: 1 to 5 wt%, SiO ₂ / A high-carbon ferrochrome style in which a high-carbon ferrochrome molten slag having a mass ratio of MgO of 0.95 or more and a temperature of 1300 to 1650 ° C. is crushed to produce a spherical high-carbon ferrochrome crushed slag having a particle size of 0.1 to 5.0 mm. Manufacturing method of crushed slag.   The high-carbon ferrochrome wind according to claim 4, wherein the high-carbon ferrochrome molten slag is subjected to air-blasting using a main nozzle for air-blasting and an upper nozzle for preventing scattering provided above the main nozzle for air-blasting. Manufacturing method of crushed slag.   An abrasive material produced by the method for producing high-carbon ferrochrome-blasted slag according to any one of claims 1 to 5.

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