JPH02115313A - Operating method for converter and cast pig used therefor - Google Patents

Abstract

PURPOSE:To execute production as planned by preheating the cast pig obtained by pretreating molten iron and casting the pretreated molten iron into a specified shape by a hot-air heater, charging the cast pig into a converter, adding molten iron, and carrying out refining in the converter while mixing stored cast pig in deficiency of molten iron. CONSTITUTION:The molten iron desiliconized, dephosphorized, and desulfurized by pretreatment is used, and the cast pig for a converter having ruggednesses on the surface, having <=80% absolute volume, and capable of being efficiently heated is cast. When the molten iron is deficient for the production planning, the cast pig is charged into a batch packed bed type hot-air heater 1 placed on a hot air generator 4, the hot air generated in the generator 4 by a secondary-air inlet pipe 6 and a burner 5 is introduced into the heater 1 through an air hole 3 to preheat the cast pig to about 800 deg.C. The preheated cast pig is charged into the converter, pretreated molten iron is then charged, blowing is started, and the specified converter operation is performed. As a result, production can be executed as planned even in deficiency of molten iron.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a converter operating method and a pig iron used therein.

[Prior Art] In recent years, in converter steel manufacturing, there has been a trend toward implementing 100% hot metal pretreatment pig iron blending operations with the intention of reducing costs and improving quality.

In such pretreated pig iron, the removal of Si, S, and P is sufficiently performed, and the carbon content is also low, so that the heat source in converter steelmaking tends to be insufficient.

On the other hand, since the amount of steel produced in a converter fluctuates significantly compared to the amount of hot metal produced, it is necessary to use high-quality scrap or pretreated cold pig iron in order to maintain its elasticity and stabilize the quality of steel production. . In this case, the amount of heat for steelmaking in the converter is further insufficient.

As a heat compensation means to compensate for such a lack of heat source, conventionally,
These include post-compassion, carbonaceous addition, and charge preheating.

Post-compassion technology is a technology in which the CO gas generated in the steel bath during converter operation is reacted with 02 in the furnace to become CO2, and the heat generated at that time is transferred to molten steel. .

As for heat compensation by adding carbonaceous materials, there is a method of adding carbonaceous materials by injection from the bottom (addition from the top of the IT furnace).The added carbonaceous materials are burned in the steel bath or on the surface of the steel bath, and are further generated. CO gas is a technology that applies heat to the steel bath by the above-mentioned post-compression method. According to this method, considerable heat compensation is possible depending on the amount of carbonaceous material added, but there are problems such as vulcanization from the carbonaceous material and melting of the refractory due to combustion heat on the steel bath surface, as well as an extension of the refining time. There is a limit to the amount of heat that can be applied.

Furthermore, the conventional shape of the pig iron is not suitable for gas heating, so the heating efficiency is low.

Further, Japanese Patent Publication No. 63-42685 discloses a method in which a solid material is continuously charged into a reactor and the material is directly heated by the gas generated from one reactor. This technology directly exchanges the generated gas with continuous materials such as steel scrap, oily steel scrap, lime, etc., so the amount of material
It requires a perfect balance of ingredients, shape and product quality, and it is not easy to melt the target 'M' species.

[Problem to be solved by the invention]

According to the current heat compensation technology, the amount of heat compensation in post-compression is small at about 4% in terms of calorific value, and although the amount of heat compensation is sufficient with the addition of carbonaceous material, there is a problem of deterioration of the quality of steel due to vulcanization, and In both cases, a large amount of heat load poses a problem in terms of cost.

The object of the present invention is to solve these problems.

[Means to solve the problem]

In the present invention, pig iron that has been pre-treated and cast into a specific shape is charged into a batch type packed bed hot air heater, and hot air is blown into the heater to preheat the pig iron to, for example, 800°C. , is a converter operating method characterized by charging the preheated pig iron into a converter, adding it to hot metal and performing converter refining, and also a converter mold for use in carrying out this method. This is pig iron for a converter consisting of a single piece with an uneven surface and a shape with a single piece performance rate of 80% or less.

For such molded pig iron, the shape of the pig iron is determined so that the heating efficiency is good in the packed bed type hot air heater, the specified mold is manufactured, it is set in the pig iron casting machine, and the pig iron is used using this casting machine. Then, the pretreated hot metal obtained by applying the currently commonly practiced hot metal pretreatment technique is cast into a shape having a good heating efficiency.

In the present invention, the molded pig iron thus obtained is charged into a packed bed type hot air heater, heated to a predetermined temperature, and then promptly charged into a converter.

[Effect] The structure and operation of the present invention will be explained in detail below.

(1) Cold iron source to be used The most desirable thing is that the composition of the hot metal charged into the converter and the composition of the molded pig iron charged after heating are almost the same. Considering cost and quality, preliminary treatment is to remove Si and P.
, those subjected to S-removal are suitable.

That is, as a source of cold iron, a type pig iron made by casting pretreated hot metal is used. Such type pig iron is low P, low S, and low Si type pig.

(2) Method of thermal compensation In general, there are two ways to heat an object: (1) Heating by using a large amount of low-density thermal energy; Heating by using a small amount of high-density thermal energy; ■ Heating by using a large amount of high-density thermal energy. heating, and is determined mainly by the heating temperature reached.

In other words, the heating temperature reached is in the low to medium temperature range, that is, approximately 100%.
(1) or (2) up to 0℃, ■ or (J
heating is common.

The heating temperature of this technology is a maximum of 1000°C, and the above (1)
By this method, it is possible to heat the steel using inexpensive gases such as blast furnace gas, coke oven gas, converter gas, or mixed gases thereof, which are generated in large quantities in steel plants.

By externally preheating the pig iron to a medium temperature (for example, 800°C) for heat compensation, there is no contamination such as sulfur due to heat compensation.

■ Gas heating, which is most suitable for preheating in the low to medium temperature range, can be used and is economical.

FIG. 4 shows the relationship between the preheating temperature of high-purity iron and the blending ratio, which allows the preheating temperature to be determined according to the blending ratio.

(3) Pig shape suitable for gas heating When the pig iron is charged into the heating furnace, the better the heating gas flow, the more
Heating efficiency is improved. Therefore, the heat transfer performance was compared by creating irregularities on the surface of the mold pig iron and displaying the irregularities as a single actual rate. FIGS. 2(a) to 2(d) illustrate such a molded pig iron 10. Here, the unit performance rate is a value expressed as a percentage of the ratio of the volume of the pig iron to the volume of the smallest rectangular parallelepiped circumscribing the single pig pig.

In the batch type packed bed hot air heater shown in Fig. 1,
FIG. 3 shows the relationship between the individual performance rate and heating efficiency when heating the mold pig iron. Good heating efficiency can be obtained when the actual volume rate is 80% or less.

[Example] A converter operation according to the method of the present invention was carried out in a 200 ton top-bottom blowing converter.

A pretreated pig iron having the shape shown in FIG. 2(c) and having the following hot metal components after pretreatment was manufactured, and this was cast into a predetermined mold.

C: 4.21% by weight Si: O, 01% by weight Mn: 0.24% by weight P: 0.03% by weight S: 0.02% by weight The circumscribed rectangular parallelepiped of this type is 10cm wide x 30cm long.
cm x height 20 cm, the single performance rate is approximately 69.3%.

Next, this molded pig iron is charged into a batch-type packed bed heater l shown in FIG. 1 and heated. This batch type packed bed type hot air heater 1 is equipped with a hot air vent 3 at the bottom of a heating/charging pot 2. The heating/charging pan 2 is placed on a hot air generating furnace 4 equipped with a burner 5 and a secondary air introduction pipe 6 to be heated. The internal volume of this heating/charging ladle 2 is 5 to 2 of the heat throughput of the converter.
It should be large enough to store 0% cold pig iron. Further, a removable lid 8 is provided, and this lid 8 is provided with an exhaust gas pipe 7. Moreover, it is equipped with a hanging device (not shown), so that the contents can be easily charged into the converter.

The specifications of one example of the batch-type packed bed heater and its heating example are as follows.

Heating and charging pot shape: Inner diameter: 1.5m Filling height: 1.77m Charging amount: 14 tons (compound ratio 7%) Heating temperature: 2800℃ Heating time: lhr Heating furnace and charging m: Initial temperature 400 ℃ Initial temperature of cold pig iron: lO℃ Single actual rate: 0.64 Required heat amount: QN = 14000 kg x 0, 2 K c a 127 kg ”CX (80
0-10)'C = 2.2X10 KcaI2/hr Heating gas temperature: 100℃ Exhaust gas temperature = 400℃ (average) Heat gas amount: =to, 5xt'o Nrr? /hr Calorie supply: Qg=10-5XIOxlooo.

X 0.3 B = 4.0X10 KcaQ/hr Thermal efficiency: = 55.0 (%) The converter was preheated to 800°C with the above-mentioned batch type filling type hot air heater after carrying out the prescribed furnace repair after tapping the steel. The molded pig iron was charged, followed by 186 tons of pretreated hot metal, and blowing was started. After the start of blowing, normal converter operation was carried out.

Comparative Example A charcoal material top addition method was carried out using a 100 ton top and bottom blowing converter. An example of operation when the scrap ratio was increased by 20% was as follows. In addition, a conventional conventional example is shown together with a comparative example.

Differences from the normal base were listed for impurity components, steel production yield, and amount of corrosion loss of refractories.

Comparative example Regular hot metal: 70 tons (90 tons) Scrap: 30 tons (10 tons) Heat source for heating: 8 tons (Ol-ton) (coke) Sub-materials (lime etc.) + 3.91-tons (1,,5 )-n)
Steel making time - 43 minutes (18 minutes) Impurity components: +
0.2 (Base) (Cu+Ni+Cr
) Steel production yield: -2.3% (Base) Amount of corrosion of refractories: +25% (Base) [Effects of the invention] When there is a shortage of hot metal for the production plan 1 For example, (a) The blast furnace is malfunctioning. , when the required amount of hot metal is not produced.

(b) When there is a shortage of hot metal during blast furnace renovation, (c) When there is a shortage of hot metal when there is an economic fluctuation and the economy is on the upswing, the production plan is achieved by blending the molded pig iron that was stockpiled at this time. be able to.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of a batch-type packed bed hot air heater used in the implementation of the present invention, Fig. 2 is a perspective view showing an example of the molded pig iron of the present invention, and Fig. 3 is a graph showing the individual performance rate and heating efficiency. A graph illustrating the relationship, FIG. 4 is a graph showing the relationship between preheating temperature and blending ratio. ■-...Batch type packed bed hot air heater 2...Heating/charging pot 3...Hot air vent 4...Hot air generation furnace 5...Burner 6...Secondary air pipe 7.・・Exhaust gas pipe 8・−・Lid IO・−・Type pig

Claims (1)

[Scope of Claims] 1 Pig iron that has been pretreated and cast into a specific shape is charged into a batch-type packed bed hot air heater, and hot air is blown into the heater to preheat the pig iron. A method of operating a converter, characterized in that the preheated pig iron is charged into a converter, and the preheated pig iron is added to hot metal and subjected to converter refining. 2. Form iron for converter consisting of a single piece with an uneven surface and a shape with a single piece performance rate of 80% or less.