JPS608284B2 - Manufacturing method of briquettes for modified carburizers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a ricket of a modified recarburizer for a low-frequency foundry furnace.

Conventionally, as a controlled carburizing material for low-frequency furnaces, compared to other hot metal furnaces, the molten metal has a slower carburizing property, so it has poor carburizing properties.
Therefore, at present, the electrode waste used as a carburizing material is crushed and sieved and used as a lump of about 5 to 6 ribs, or it is carburized in the form of fine particles.

However, in the former method, the crushing step, crushing process,
Moreover, the cost is high, and in the case of the latter, most of it scatters during carburization, resulting in a significant decrease in the carburization rate.

At the same time, there are problems such as the work environment being severely disturbed.
The present inventor provides a carburizer that uses carbonaceous electrode powder as a low-frequency furnace-adjusted carburizer and briquettes it to provide high strength and easily carburize.

Electrode powder has a higher fixed carbon content than other carbons and is extremely suitable as a recarburizing material for hot metal, but in powder form it has the above-mentioned drawbacks. Therefore, a binder is required to briquette it. Examples of binders include carboxymethyl cellulose (hereinafter referred to as CMC), which is used as a recarburizing material for arc furnaces, starch, and sulfite pulp waste liquid, but briquettes made using these binders are not bonded. The effect is obtained but the molten metal cannot be carburized in a short time, or the binding effect and carburization are sufficient but a large amount of binder is required, resulting in a decrease in fixed carbon or the binder in the briquettes being melted and damaged. This is undesirable because the briquettes are destroyed and pulverized, resulting in poor carburization and other negative effects. The present invention aims to provide a method for producing briquettes that are strong and can be easily carburized, which is characterized by using polyvinyl alcohol (hereinafter referred to as PVA) and CMC as binders in combination.

By using PVA and CMC in combination, it is possible to obtain briquettes with excellent carburization properties that do not compensate for the drawbacks that normally occur when each of these binders is used alone. In the present invention, a combination ratio (weight) of PVA and CMC having a degree of saponification of 75 to 99 mol % and a degree of polymerization of 300 to 2,400 (weight) of 8:2 to 5:5 is added to the weight part of the electrode powder 10 as a binder. It is characterized by adding and mixing 5 to 1.5 parts by weight, and then melting and molding in a state where the moisture content is 10 to 20%.

PVA as a binder has a polymerization degree of 300 to 2500, preferably 1700 to 2400, and a saponification degree of 75 to 9.
The product contains 9 mol%, preferably 75 to 88 mol%, because PVA requires water lacquer properties.

The reason why the combined use ratio of PVA and CMC is 8:2 to 5:5 is that it is not easily carburized in a melt wound outside this range.

In other words, if PVA exceeds 8% by weight, there is no problem in terms of strength, but if it is added to the molten metal, the briquettes will collapse and turn into powder, and will not be carburized. If it does not dissolve or requires a considerable amount of time to be carburized, it is meaningless as a controlled carburizing material.

The amount of the binder that uses PVA and CMC in combination is 0.5 to 1.5 parts by weight relative to the electrode powder.If the amount is less than 0.5 parts by weight, the strength of the briquettes will be low, and therefore the strength of the briquettes will be reduced during transportation. Not only is it not strong enough to withstand vibrations and shocks, but it turns into powder when poured into molten metal.

Moreover, if it exceeds 1.5 parts by weight, the fixed carbon content decreases and it cannot be used as a modified carburizing material for casting.

In addition, the binder of the present invention can be used in the form of a powder weight or an aqueous solution at the above ratio, but in the case of an aqueous solution, the viscosity varies depending on the ratio of PVA and CMC, so the amount of added water should be taken into consideration. There is a need to.

In order to uniformly mix the electrode powder and the binder, it is preferable to use the binder in powder form. The moisture content of the carbon material during molding is 1
A moisture content of 0 to 20% is preferable, and if the moisture content is less than 10%, it will be difficult to mold, and if it exceeds 20%, the molded briquettes will become porous after drying, causing a decrease in strength. shows a large tendency to The briquettes thus formed have sufficient strength to withstand transportation and are easily carburized into molten metal on the furnace surface.

In this way, the briquettes obtained according to the present invention are easily carburized in a short time without collapsing or pulverizing on the furnace surface, and are not only able to prevent various negative effects that occur in the case of ordinary powder carburization, but also are economical. You can obtain stable operations and products.

The briquettes obtained by this method can be used not only as a recarburizing material for low-frequency furnace preparation, but also as a carbon material for molten iron.

Next, the effects of the present invention will be explained based on examples.

Examples 1 to 4 PVA and C in 10 parts by weight of electrode powder having a fixed carbon content of %
Adding 1 part by weight of MC at various combination ratios,
After drying for about 3 minutes, 1 part by weight of water was added and the mixture was mixed for 2 minutes, and then molded into briquettes using a double roll press.

The molded briquettes were dried in a 120 to 150 qo hot air dryer until they had a constant weight. Table 1 shows these conditions and the measurement results of strength and carburization.

Comparative Examples 1 to 7 In briquetting in Example 1, outside the scope of the present invention and P
Comparative examples were made in which VA, starch, and CMC were added alone in different amounts, and the molding and briquetting were performed in the same manner, and the strength and carburization properties were measured.

These conditions and results are shown in Table 1.

The physical properties of the priquettes were measured by the following method.

1 Strength (compressive strength) The briquettes were placed on a commercially available automatic plate and gently pressed by hand, and the maximum load when the briquettes broke was defined as the strength.

2. Briquettes were placed in a molten metal with a collapsibility of 1500 qo, and the presence or absence of disintegration was observed during the carburization process.

3. Briquettes were put into a molten metal having a powder content of 1500 qo, and observed whether they would disintegrate and produce powder during the carburization process.

Items that are powdery are considered defective due to a decrease in carburization rate. 4. Carburization: A briquette was placed in a molten metal of 1500 qo, and the state of the briquette being melted and carburized was observed.

5 Judgment Criteria ◎: Carburization time of 5 minutes or less, in which the briquettes are carburized while being melted from the surface.

○: The briquette is carburized while being melted from the surface, but the carburization time is long.

△: The briquettes were not melted at all, resulting in poor carburization.

×: The briquettes were dusty and scattered, resulting in poor carburization.

Claims (1)

[Claims] 1 Saponification degree 75-99 mol%, polymerization degree 300-240
0.0 polyvinyl alcohol and carboxymethyl cellulose were added to the electrode powder in a weight ratio of 8:2 to 5:5.
A method for producing a briquette for a modified carburized material, which comprises adding and mixing 5 to 1.5% by weight, adjusting the moisture content of the molding material to 10 to 20%, and then kneading and molding.