JPS5992151A - Production of free-cutting lead steel by continuous casting method - Google Patents

Abstract

PURPOSE:To prevent the generation of lead fume and lead dust and to melt and disperse uniformly lead by covering lead particles or lead compd. particles with an iron hoop, molding the particles to a wire shape, adding the wire to the part in a tundish onto which a molten steel drops and providing a stirring mechanism between said part and a tundish nozzle. CONSTITUTION:A wire 7 formed by covering lead particles or lead compd. particles with an ultrathin iron hoop is supplied to the part A onto which the molten steel from a ladle 1 drops or to the part B right above a tundish nozzle 5. A stirring mechanism for a molten steel 2 is provided between the part A and the nozzle 5 in the case of supplying the wire 7 to the part A where the molten steel from the ladle 1 drops. Then the molten steel 2 is forcibly stirred before it arrives at the nozzle 5, and the excess lead is prevented by a gate from being mixed with the molten steel in a casting mold. It is possible to use a porous plug and an immersion lanse as the stirring mechanism in the case of supplying the wire 7 to the part B right above the nozzle 5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing lead free-cutting steel by a continuous casting method. Lead has a low melting point and boiling point, and a high vapor pressure, so when lead is added to molten steel for the purpose of producing lead free-cutting copper, it is often used in addition 1. The generation of lead-containing dust or toxic gas is unavoidable.

Since the ingot-making method is better at dealing with such problems, lead free-cutting steel has conventionally been produced in Japan by the ingot-making method.

On the other hand, the continuous casting method (hereinafter referred to as the renzu method) generally has the advantages of higher yield and production efficiency than the ingot casting method, so the production of lead free-cutting copper using the renzu method is more effective. Although this is desirable, it has the following problems.

That is, in the continuous VD method, molten steel in a ladle is received by a -H tundish, and the molten steel is normally distributed and supplied to a plurality of molds. In this way, the complicated process of injecting molten steel from the ladle into the tandice I and from the tandice to the mold is required, and because the length of the tundish is extremely long, usually 4 to 7 meters, there is no chance that the molten steel will come into contact with the atmosphere. In addition, the molten steel in the tundish is violently stirred by the injection flow from the ladle, and furthermore, it is dispersed at 200 to 300 °C.
Even if lead is added to the molten steel stream for the purpose of manufacturing free-cutting copper, the aforementioned black smoke consisting of lead dust and lead fume is generated in many cans.
Unfortunately, there was a problem with the health management of the workers. There is a risk of dissolution of lead into steel by 0.22%.

The present inventors previously proposed a method for manufacturing lead free-cutting steel using a continuous casting method in Japanese Patent Application Laid-Open No. 57-17357.

It consists of adding lead particles to molten steel together with an inert carrier gas. In step 1-, unmelted lead is removed by installing a drain in the tundish, while the area around the molten steel injection flow between the tundish and the mold is shielded to recover the lead fume generated. , IF prevents oxidation of lead due to the surrounding atmosphere.

By adopting such a method, the conductivity was improved, but there was a large amount of lead that was not used due to the dispersion of lead fume and 1.7, and there were many hygienic problems. I couldn't think of anything.

Thus, the object of the present invention is to produce lead free-cutting steel with a high lead yield without causing health and safety problems by continuous casting. ! It is to provide law.

Furthermore, it is an object of the present invention to provide a method for manufacturing lead free-cutting copper using a continuous casting method, which allows lead to be added uniformly and in a controlled manner easily and easily.

The present invention provides an improved method for manufacturing lead free-cutting pieces using a continuous casting method in which molten steel in a ladle is supplied to a mold via a tongue tissue. In this method, lead grains or lead compound grains are formed into a linear shape with an iron hoop to be nucleated.The wire obtained in steps 1 to 1 is placed in the hot water area of the ladle or directly above the mold using a tamp and r. Addition 17 to the molten steel in the tundish, and if the addition position of the wire is the dripping part from the ladle, the stirring mechanism for the molten steel in the tundish from the dripping part from the ladle to the tundish nozzle. Further, when the addition position of the wire is directly above the mold, a mechanism for stirring the molten steel in the tundish directly above the mold is provided to uniformly disperse the added lead.

The wire for adding lead is obtained by filling a hollow wire made of an ultra-thin iron hoop with lead particles or lead compound particles (e.g., 1) bO, PbS with a particle size of 0.1 to 0.8. Anything is fine.

According to the present invention, the production of lead fume and lead dust during addition is prevented because the lead grains are powdered, and furthermore, the lead particles are formed into a wire shape and the 7'r material is mechanically tanned. Since it can be pushed into the molten steel, it can be easily supplied into the molten steel. When using lead compound particles, the effect of lowering the vapor pressure of lead is expected.

The part where the wire for adding lead falls from the ladle or the mold i
(If lead is supplied to the molten steel in the tundish above, the stirring flow of the molten steel itself can be effectively used to uniformly melt and disperse the added lead, which is advantageous.

However, it has been found that the stirring flow of the molten steel itself is insufficient to achieve completely uniform dispersion of the added lead, so according to the present invention, a mechanism for stirring the molten steel within the tundish is provided in the tundish.

In order to dissolve and disperse the added lead as uniformly as possible, this stirring mechanism is used to feed the wire from the ladle to the dripping part from the tundish nozzle. It will be established as appropriate until the end.

In this case, the molten steel stirring mechanism may be, for example, at least one pipe provided at the bottom of the tongue tissue, a porous plug for inert gas injection provided at the bottom of the tongue tissue, or a mechanism immersed into the molten steel from the top of the tongue tissue. An immersion lance for inert gas injection or the like can be used alone or in appropriate combination.

The wire is supplied to the molten steel in the tundish directly above the mold, that is, the continuous casting mold, by utilizing the turbulent flow of the molten steel near the tundish nozzle, and the lead-added material is This is an effective method when the amount is small. When feeding the wire to this position, the tundish is equipped with an appropriate molten steel stirring mechanism that stirs the molten steel in the tundish directly above the mold. Porous plugs or immersion lances from above can likewise be used alone or in suitable combinations.

Although no particular mention was made of the oxidation of the molten steel in the tundish or the molten steel poured into the mold and the generation of lead fume due to this, the oxidation of molten steel and the generation of lead fume due to this is possible even in the present invention. It is necessary to prevent this from occurring, and it is necessary to isolate the molten steel from the atmosphere by appropriate means.

The invention will now be further elucidated in conjunction with the accompanying drawings.

Attached figure m1kj is a schematic conceptual explanatory diagram showing an outline of the continuous l* casting method for carrying out the method according to the present invention.

One ladle of molten steel 2 passes through a sliding nozzle 3 (not shown), is supplied into a tundish 4, and then passes through a mendish nozzle 5 to a plurality of continuous casting molds 6 (usually 3 to 4 molds).
0.1 (one of which is shown in the figure) is injected into J'+.

In the illustrated example, only the inside of the tongue tissue 40 is cut off from the atmosphere, but it may be shielded from the atmosphere at any arbitrary point if necessary.

According to the present invention, the wire 7, which is made of lead grains or lead compound grains, is connected to the dripping part of the ladle (the part indicated by the symbol (A) in the figure) or the trough. Dish nozzle 5
The top part of the page, that is, the part of the mold (code 03 in the figure)
(indicated by ).

In the former case, it is preferable that the wire be inserted into a region within a range of about 300 degrees in diameter from the center of the dripping part. The form of this wire supply is not particularly limited;
The coiled wire 7 may simply be sent out one by one using appropriate means as needed.

In addition, when the above-mentioned wire is supplied to the dripping part (A) from the ladle, an appropriate stirring mechanism for the molten steel is connected to the tundish from the dripping part in order to ensure uniform melting and spreading of the added lead. Provided before reaching the nozzle. In the illustrated example, gaps are provided at the bottom of the tundish and at the top of the molten steel in the tundish, respectively. In addition to this, when hm Even if it settles, if the above-mentioned separation is provided, it will be mixed into the casting pot through the tundish nozzle.
It never comes.

An inert gas (e.g. argon) provided at the bottom of the tundish as a stirring mechanism for the molten steel for propelling.
There are porous plugs for blowing and submerged lances also for blowing inert gas, and these stirring mechanisms may be used alone or in combination.

Among these, the porous plug and the immersion lance can also be used as a molten steel stirring mechanism when inserting the wire 7 into the tundish nozzle part (13).

Note that these molten steel stirring mechanisms may be of any type as long as their specific structures are already well known to those skilled in the art, so further explanation will be omitted.

According to the invention, lead content 1if 0.06% to 0.30
56 lead free-cutting steel can be easily manufactured without any health and safety issues,
Moreover, lead-containing deposition can be controlled arbitrarily within the above range.

EXAMPLES According to the method shown in the accompanying drawings, lead free-cutting steel having the following composition was manufactured using the wire obtained in step 1- in which lead grains were coated with iron hoops. (r: Lpb amount 1 and Toga 0 amount) Table 1 Steel composition (iffi multiplied by %) CSi Mn P S Cu i'
l+≦0.10≦0.0150.90 0.0400.
280≦0.25 (1,2 flSSS S 1.20 0.09 (10,3300,35 Lead-added wire has an outer diameter of 6 m + n (diameter), and a hoop thickness of 04 to 0.6
A hollow wire made of mild steel between the wires was filled with lead grains with an average diameter of about 0.5 l (diameter) at 150 to 1 (i 0 ?) per 1 m of wire length.The results are shown in Table 2. Because of the insertion, the PB yield was considerably poor.In this case, a tan tissue with double upper and lower openings as shown in the attached drawing was used.

In test tube No. 2, a wire was inserted directly above the tundish nozzle, and argon gas was blown through a bolus norag (not shown) provided at the bottom of the tundish.

In this case, a single sheath was used, which was placed only at the bottom of the tundish.

Trial IIl! Ji No. 9331d, a wire was added to the dripping part from the ladle. In this case, a double passage was provided as shown.

Test No. 4 shows an example of wire addition directly above the strand nozzle, and in particular in this case, the wire was supplied while blowing arcon gas into the molten steel from the tip of the immersion lance.

Table 2 1 0.35 0.03 or less 8,6
2 0.20 0.14 7(1,0
30,300,1653,3 40,250,1664,0 Next, regarding the case of test number 2, the Pb analysis of the cast slab was performed using the 400X3 at a position 3 m from the meniscus.
PB content is 011-0.15% in the cross section of 00mm
was within the range. It can be seen that Pb is extremely uniformly dispersed.

Regarding the case of test number 3, PB as the casting time elapsed.
Figure 2 shows the change in metallurgical content.

As can be seen from these results, according to the present invention, in all cases, Pb is uniformly dissolved and dispersed, and the yield of Pb is also improved.

A simplified conceptual diagram of the method of making poetry, and the second figure is
1 is a graph showing the Pi) distribution of slabs obtained by the method according to the present invention.

DESCRIPTION OF SYMBOLS 1... Ladle, 2... Molten steel, 3... Sliding nozzle, 4... Tundish, 5... Tundish nozzle, 6... Mold, 7... Wire, (A) ...Boiling water part, 03)...Button, J type position" 2 parts.

Applicant Agent Patent Attorney Hiroshi

Claims (2)

[Claims] (1) A method for manufacturing lead free-cutting steel using a continuous casting method in which molten steel in a ladle is supplied to a mold via a tundish, in which lead grains or lead compound grains are covered with an iron hoop and formed into a linear shape. The obtained wire is added to the molten steel in the tundish at the part where the hot water drips from the ladle, and a stirring material structure is provided for the molten steel in the tundish between the part where the hot water drips from the ladle and the tundish nozzle. A method for producing lead free-cutting steel characterized by uniformly dispersing added lead. (2) A method for producing lead free-cutting steel by a continuous casting method in which molten steel from a ladle is supplied to a mold via a tundish,
A wire obtained by agitating lead particles or lead compound particles with an iron hoop and forming them into a linear shape is added to the molten steel in the tundish directly above the mold, and the molten steel in the tundish directly above the fishing mold is stirred. A method for producing lead free-cutting steel, characterized by providing a mechanism to uniformly disperse added lead.