JPS6075513A - Treatment of molten iron or molten steel - Google Patents

Abstract

PURPOSE:To prevent moisture from entering molten iron or molten steel and to utilize the sensible heat of quick lime discharged from a lime calcining kiln at a high temp. by feeding the quick lime to the molten metal without reducing the high temp. CONSTITUTION:Quick lime discharged from a lime calcining kiln at a high temp. is crushed with a crusher 3 at the high temp. and classified with a classifier 20. The classified quick lime is stored in a hopper 21 without reducing the high temp. The quick lime stored at the high temp. is blown into molten iron or molten steel from a blowing lance 24. Moisture is absorbed in quick lime at ordinary temp., and when the quick lime is used, H2 is dissolved in molten steel to cause hydrogen embrittlement. By this method, such hydrogen embrittlement is prevented, and the sensible heat of the quick lime is utilized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for de-S and de-P treatment of hot metal and molten steel by using quicklime in an anhydrous and high-temperature state.

(Conventional technology and problems to be solved) In recent years, quality requirements for steel materials have become stricter depending on the conditions of use.
Hot metal and molten steel processing methods such as degassing have been developed. Among these treatment methods, there is a method in which quicklime powder is blown into the molten steel to cause desulfurization inclusions to float, thereby improving the quality of the steel.

However, the quicklime powder used in this method absorbs a large amount of moisture from the air, and this moisture enters the molten steel as H2, which is captured in the steel during the solidification process and is used to meet strict quality requirements. Hydrogen embrittlement may occur in steel, which may lead to destruction of structures.

For the above reasons, conventional powder blowing degassing equipment (RH-
It was necessary to perform de(H) treatment using a DH device). In addition, this degassing process causes the temperature of the molten steel to drop.
It was necessary to raise the temperature of the molten steel in advance. These are factors that significantly increase the cost of producing steel ingots.

In order to solve these problems, there is a demand for low-moisture quicklime for steelmaking, and the method for producing it is to react the quicklime skin with carbon dioxide gas to form carbonated lime.

0.0-Fe203-Ae20. There is a known method of fusing mixtures of such materials at high temperatures to form a compound that is difficult to absorb water, but this method is expensive in terms of accounting costs and requires a large amount of lime to supplement the lime content necessary for dephosphorization and desulfurization. Since it is necessary to charge quicklime whose skin is made of lime carbonate or the above-mentioned composite, there are major disadvantages as the storage and charging equipment becomes larger and the amount of coating material charged into the steelmaking furnace increases.

There is also a method of heating quicklime just before blowing it in and quickly blowing it in before it absorbs moisture again, but this is expensive due to the installation of heating equipment and the like.

(Structure of the Invention) The present invention utilizes the sensible heat of high-temperature quicklime fired in a lime kiln to produce high-grade steel that eliminates the degassing step in hot metal and molten steel processing by using quicklime in a moisture-free high-temperature state. It enables manufacturing.

Figure 1 shows an example of the material balance of (H) in a converter, and as seen in the figure, (H) is mixed into the steel.
The OaO added during processing is a major factor in H).

At this time, the amount of moisture brought in is greatly influenced by the temperature of the OaO, as shown in FIG.

Therefore, in the present invention, when supplying aaO into hot metal or molten steel, the calcined CaO is not cooled once and is kept at a high temperature of 50°C or higher before being blown into the hot metal or molten steel. It is.

(Example) The processing flow according to the present invention is shown below.

↓ Next, the drawing of the apparatus for carrying out the method of the present invention is shown in 4-4. Show and explain.

In Figure 3, the rotary kiln] - at] 300°C
1. The raw stone fired at ~100°C is taken out of the cooler 2 by opening the gate valve 8 of the chute 7 at a high temperature of 1,300°C to 1,000°C, for example, and taken out of the cooler 2 into a primary crusher equipped with an intermediate humper 9. ] Roughly crush at 0. The crusher 1o is, for example, a roller mill with a water-cooled structure,
Coarsely crushed quicklime particles or powder are sent to the crusher 3 via the chute 11 and are crushed to a predetermined particle size.

The crushed low-moisture quicklime powder is sent to the pressure pipe 1 by the blower 18.
9 and is separated into a pumped fluid and quicklime powder by a classifier (for example, a cyclone) 20, and the quicklime powder descends and is stored in a storage hopper 21, which is provided at the lower end of the hopper as required.

It is cut out into a blowing tank 23 as appropriate by a discharge device 22,
Low-moisture quicklime is blown into the hot metal and molten steel through the lance 24.

In the present invention, the crusher is placed on the side of the lime calcining furnace, but depending on the factory layout, it is also possible to place the crusher on the side of the on-site machine.

That is, the high-temperature lime immediately after calcination may be placed in an insulated container and transported to the pulverizer at the site of use.

Although the fluid used for transportation from the crusher is discharged from the classifier 20, it exchanges heat with the blown N2, is cooled, and then circulates to the blower 18, thereby further enhancing the effects of the present invention.

[Example] adopted for molten steel treatment according to the present configuration described above is shown below.

6- Temperature of calcined limestone〉 1 (after 24 hours) ...900℃↓ When blowing is performed at about 750℃ using N2 as a carrier gas, the amount of attached moisture is about 0.8%, compared to the conventional 5 to 6 As a result, (H) in the molten steel after blowing
) i- is 1 to 1.5 p compared to the conventional value of 3 to 5 ppm
It was about pm.

7- (Effects of the Invention) According to the present invention, there is no need for prior treatment to obtain low-moisture quicklime (e.g., carbonate calcification treatment), which was conventionally used, and low hydrogen content, which was achieved by conventional techniques, is unnecessary. Steel is obtained, and 1
For the above steel types, the degassing (H) step can be omitted, and the cost of producing steel ingots can be significantly reduced.

[Brief explanation of the drawing]

Figure 1 shows the H balance during blowing. FIG. 2 is a graph showing the relationship between the initial temperature of limestone, the elapsed time, and the amount of moisture absorbed. FIG. 3 is an explanatory diagram of an apparatus for carrying out the method of the present invention. 1... Rotary kiln 2... Cooler 5...
Crusher 7...Chute 8...Gate valve 9...Hopper 10...Crusher 11...Chute 1B...Blower 19...Pressure pipe 20...Classifier 21. ...Storage hopper 22.
...Discharge device 23...Suction tank 8- 24...Lance 9- Rod/ Figure 2: Open (/11/r,)

Claims (1)

[Claims] S removal by blowing 0.20 grade powder into hot metal or molten steel. In a method of performing treatments such as dephosphorization, 1. High-temperature quicklime discharged from a lime kiln is crushed at high temperature, classified, and then stored in a hopper while maintaining the high temperature state, and the quicklime powder is injected into hot metal through a blowing lance. Or a method for treating molten pig iron or molten steel, characterized by supplying it into molten steel.