KR100307578B1 - Manufacturing method of pure iron powder by carburizing and decarburization from waste steel cans - Google Patents

Abstract

The present invention produces high value by producing pure iron powder, which is a raw material of various iron-based sintered products through carburizing and decarburization from a thin plate form of waste beverage without dissolving waste cans, thereby relying on imports from foreign countries. It is a very useful invention that can reduce the national waste by replacing iron powder and reap the effects of environmental protection and the like by reusing waste resources that pollute the environment.

Description

Process for producing pure iron powder by carburizing-decarburization from waste steel cans for beverages

The present invention relates to a method for producing pure iron powder from waste steel cans for beverages, and more particularly, to a method for producing pure iron powder from waste steel cans by carburizing-decarburization.

The age we live in now is due to the development of material civilization and the advancement of industrial society, and the kinds of waste are exploding and the amount is explosively increasing, finally causing serious social problems as the main cause of environmental pollution. In particular, the amount of steel cans and aluminum cans for waste beverages among metal wastes is increasing rapidly with increasing vending machines or changing food and beverage consumption patterns. As of 1991, domestic can demand is about 140,000 tons per year, an average annual growth rate of more than 23%. Unlike aluminum cans, however, steel cans for waste beverages are made of aluminum alloy, not cover and tap, and the amount of impurities such as Ti, Sn, Ni, and Cr oxides from the paint during melting In many cases, manufacture of the thin plate material for steel can production by remelting is virtually impossible. Therefore, until now, waste steel cans are not recycled, and most of them are disposed of or disposed of together with general garbage, thus increasing the environmental pollution.

This is an enormous waste for us who are absolutely short of resources, and the recovery of waste steel cans is a major research issue in terms of resource recycling and environmental pollution prevention. Since the government has produced more than 100,000 tons of steel annually, steel mills have to recycle more than 20% since 1994, and since 1998, the government has shown a great interest such as mandatory recycling of waste steel cans of more than 40% of production. Some steelmakers are scrapping waste steel cans and reusing them in small quantities, but their utilization is still insignificant at about 7.5% of the steel cans. It's a costly closure.

The present invention is to develop a high value-added material for new uses if recycling the resource value of the waste steel cans, as a part of the invention was to invent a method for manufacturing pure iron powder from steel cans for waste beverages, To date, no attempt has been made at home or abroad.

That is, the present invention produces high value by producing pure iron powder, which is a raw material of various iron-based sintered products, through carburizing and decarburization from the original plate without dissolving the steel can for waste beverage, thereby relying on imports from foreign countries. It is intended to replace iron powder.

Hereinafter, the manufacturing method of the present invention will be described step by step.

The present invention is largely a pre-treatment step to collect the waste steel cans to be easily put into the heating furnace, and to heat the cut steel cans in a heating furnace of 400 ℃ ~ 700 ℃ for about 30 minutes to the aluminum layer attached to the paint layer and can Separation process for separating cover and tap, carburizing process for carburizing steel cans, grinding process for powdering carburized steel cans, and decarburizing pulverized can powder It is made of a decarburization process.

Each process is described in more detail as follows.

The pretreatment process is to collect the waste steel cans left in the market and cut them into a suitable size so that they can be easily put into a heating furnace, and the collected steel cans are usually closed by a waste steel can squeezed material (450 × 300 × 200 mm) pressed by a press. It is delivered to the steel can processing plant. Waste steel cans are mainly made up of two-piece or three-piece steel cans for beverages. Therefore, the compacted material should be cut by a cutting device to a size suitable to be dismantled and put into a heating furnace.

The separation process is followed by putting the cut two-piece and three-piece steel cans into a heating furnace and heating them at 400 ° C. to 700 ° C. for about 30 minutes to cover the paint layer, the aluminum alloy cover and the tab ( tap).

At this time, the paint layer on the inner surface of the two-piece steel can began to decompose from 400 ℃ or lower, and as the temperature rose, complete peeling occurred from the Fe layer.The resin was completely decomposed when held at 700 ℃ for 30 minutes. Part of the layer was oxidized. On the other hand, the paint layer on the outer surface of the steel can was pyrolyzed first at around 500 ° C as the heating temperature was increased, and the white coat layer of TiO ₂ component was separated from the Fe layer at 650 ° C and completely peeled at 700 ° C.

On the other hand, the Sn layer on the inner surface of the three-piece steel can was oxidized at 400 ° C and the temperature was increased, so that the complete separation occurred at 500 ° C. The paint layer was removed by complete pyrolysis. However, although the white coat layer began to peel from Fe as the temperature increased, unlike the two-piece steel can, the white coat layer was not onna-zipped from the Fe layer even when held at 700 ° C for 30 minutes. Therefore, the steel can can be subjected to an external shock or vibration to peel off the white coat layer. When the steel can is impacted, the white coat layer can be peeled off even at a temperature lower than 700 ° C. At this time, because the heating temperature is high, part of the Fe layer was also oxidized, and peeling occurred in the form of an oxide with Mn dissolved in a small amount.

In addition, the separation of the aluminum alloy cover and tab from the body of the steel can is the aluminum alloy cover and tab of the upper part of the steel can, which is an Al-Mg alloy of ASTM 5000 series, is mechanically press-contacted with the body, and the melting temperature of Fe and Al is different. Because of its size, it can be easily separated. That is, since the aluminum alloy cover is thin and easily forms an oxide film like the steel can body, even if it is heated above the melting point, the wettability with the steel can body is not great, so the two parts can be separated. However, covers and tabs made of Al-Mg alloys of ASTM 5000 series start to dissolve at 575 ° C and 600 ° C, respectively, and become liquid at 615 ° C and 630 ° C, respectively, and are separated from the body. Proceeded. Therefore, the temperature suitable for separation of the aluminum cover and the tab is preferably 630 ° C., which is a solid liquid coexistence section of the aluminum alloy.

As such, the Sn layer on the inner and outer surfaces or the paint layer on the outer surface was oxidized / burned at a heating temperature of 500 ° C. to be separated and removed, and a higher heating temperature (650 ° C. to 700 ° C.) was used to remove the white coat layer containing TiO _2. C) and external vibrations were required. In addition, the aluminum alloy cover and tab on the top of the can can be removed by using the melting temperature difference between iron and aluminum alloy.

As described above, the steel cans from which the paint layer and the aluminum alloy cover and tab are removed are subjected to a carburization process so as to be easily broken. The carburizing process is used to carburize the carburizing furnace. Used. The carburized gas was blown from the bottom of the furnace to improve the flow of the gas, and the amount of gas blown was 2.2 L / min. The pretreated waste steel cans are charged into the carburizing furnace and valves are properly adjusted to prevent the explosion of propane gas. The N ₂ gas in the furnace is replaced with carburizing gas, and the austenite zone is 900 ~ 950 ℃ (930 ℃ is most preferred. After heating for about 35 ~ 45 minutes, the carburizing material was quenched in water.

The hardness value according to the carburizing time showed the maximum value (H _v 412) when the carburizing time was 40 minutes. At this time, the matrix structure was vulnerable as martensite, so it was easily broken.

The pulverization process is to obtain a polygonal and spherical particle powder of 50㎛ ~ 180㎛ size by pulverizing 2 ~ 3cm size by rapid cooling after carburizing process in order to powder the steel cans.

The decarburization process is used to make pure iron powder by decarburizing using a mixed gas of H ₂ O and H ₂ using a decarburization furnace, where the temperature of the decarburization furnace is 1 at 700 ° C. at which temperature does not suddenly sinter. After maintaining for some time, the mixture was cooled to room temperature in an H ₂ gas atmosphere to prevent reoxidation.

The decarburization reaction is as follows. Fe (C) + H ₂ O → Fe + CO + H ₂

The apparent density, flow time, compact density, densification rate, and Rattler test values of decarburized powder are as follows.

TABLE 1

The chemical composition of the decarburized powder is as follows.

TABLE 2

As described above, according to the present invention, the pure iron powder having a high Fe content and a markedly reduced impurity was obtained.

By replacing the expensive pure iron powder raw material, which is almost entirely dependent on imports, with the cheap waste steel cans manufactured by the present invention, there is a tremendous import substitution effect, and by protecting the environment by reusing waste materials that have been left unclean and polluting the environment. In addition to lowering the production cost of iron powder, it is possible to supply low-priced iron powder, thereby creating high value added up to several times the profits obtained by reusing conventional waste cans.

Claims (4)

A pretreatment step of collecting the waste steel cans for easy insertion into a heating furnace; a separation step of separating the paint layer and the aluminum alloy cover and tap attached to the cans from the cut steel cans; Carburizing from waste steel cans for beverages characterized by the carburizing process for carburizing, the carburizing process for pulverizing the carburized steel can, and the carburizing process for decarburizing the pulverized can powder. -Pure iron powder manufacturing method by the decarburization method. The method of claim 1, wherein the cut steel can introduced into the heating furnace during the separation process is heated for 30 minutes at 400 ℃ ~ 700 ℃ and the steel can is vibrated to separate the paint layer, cover and tab from the can body. Method for producing pure iron powder by carburizing-carburizing method from the waste steel can for beverage, characterized in that configured to. The carburizing process according to claim 1, wherein the carburizing process is used during the carburizing process, wherein the carburizing gas is mixed with air having a volume ratio of 10: 1 and propane gas and heated to 900 to 950 ° C for 35 to 45 minutes. Method for producing pure iron powder by carburizing-decarburizing method from waste steel can for drink, characterized in that the carburizing treatment is carried out by quenching in water after maintaining the degree. According to claim 1, during the decarburization process using a decarburization furnace (爐) to degassing, using a mixed gas of H ₂ O and H ₂ heated to 700 ℃ to maintain for about 1 hour, H to prevent reoxidation _{2 A} method for producing pure iron powder by carburizing-decarburizing from a waste steel can for drinks, which is cooled to room temperature in a gas atmosphere.