JPS59113156A - Manufacture of lead free-cutting steel - Google Patents

Abstract

PURPOSE:To accelerate the dissolution and uniform dispersion of lead particles in molten steel by adding lead to the molten steel in a tundish and by applying ultrasonic vibration to the molten steel through immersed horns for ultrasonic vibration. CONSTITUTION:Lead particles are charged into molten steel in a tundish 3 from a charging inlet 7. Refractory horns 8 each provided with an ultrasonic vibrator 10 are immersed in the part of the molten steel mixed with lead particles and/or the part of the molten steel contg. dissolved lead. By applying ultrasonic vibration, the dissolution of lead in the steel is accelerated, and lead particles and free-cutting inclusions are uniformly distributed in the steel. Gravity segregation due to the difference in specific gravity between molten steel and lead is prevented, and the yield of dissolution of lead in steel is improved.

Description

[Detailed Description of the Invention] The present invention relates to a method for producing lead free-cutting steel, which is a type of free-cutting steel, in which the rigidity of the steel is improved by the presence of free-cutting elements in the form of inclusions in the steel. The present invention relates to a method for manufacturing lead free-cutting steel that uses ultrasonic waves to uniformize the distribution of lead particles and free-cutting inclusions in the steel.

Conventionally, the manufacturing method for lead free-cutting steel is continuous casting,
In the tandish, when pouring into the mold, when pouring into the mold, and when pouring into the mold, the molten steel is poured into the molten steel at the molten steel injection port, respectively.
Fine particles of lead of about 5-mm diameter are added to the steel to precipitate free-cutting inclusions consisting of lead particles of about 10μ in size as it cools and solidifies, and/or around nonmetallic inclusions with a high solidification point. A method is used to precipitate free-cutting inclusions formed by adhesion of lead.

However, the solubility of lead in steel is very small, at most 0.3%, and this varies depending on the temperature of molten steel and the content of C, Cr, Ni, etc., so a sufficient amount of lead can be solidified. It is difficult to dissolve and precipitate. Furthermore, when lead is added, some of the lead evaporates and evaporates, which further causes gravity segregation to the bottom of the steel ingot (in the case of continuous casting, gravity segregation inside the tundish), causing lead to evaporate and evaporate. It accumulates in the tundish, causing a decrease in lead yield. Furthermore, excessive agglomeration and segregation of lead observed in the steel during cooling and solidification causes non-uniform precipitation of free-cutting inclusions after cooling and solidification.

Therefore, in manufacturing lead free-cutting steel today, it is important to promote the dissolution of lead into molten steel, and to prevent lead particles in molten steel from distributing nonmetallic inclusions with high solidification points to which lead particles are attached. It is necessary to make it uniform.

Up to now, many proposals have been made to provide an excellent method for manufacturing lead free-cutting bolts that satisfies the above requirements, but none of them are necessarily satisfactory. There wasn't.

By the way, the phenomenon of ultrasonic emulsification, in which different types of liquids that cannot be easily mixed by normal stirring are instantaneously mixed using ultrasonic energy and become cloudy, is already known. It is used to make emulsions such as water and oil, nitrous acid and p-xylene, and nitrous acid and cyclohexane.

The present inventors focused on this phenomenon and set out to utilize ultrasonic energy in the production of lead free-cutting steel.As a result, the inventors developed an immersion-type ultrasonic imaging horn to generate ultrasonic vibrations in molten steel. He discovered that by adding lead particles, it was possible to promote the dissolution and uniform dispersion of lead particles in steel, and completed the invention.

Thus, the present invention is a method of improving the lead dissolution yield during the production of lead free-cutting steel and making the fraction of lead in the steel uniform by utilizing this ultrasonic emulsification phenomenon. teeth,
In a method for producing lead free-cutting steel by adding fine particles of lead to molten steel in a tundish in continuous casting and dissolving the lead in the molten steel, the mixed part of molten steel and lead particles and/or
or applying ultrasonic vibration to the molten steel portion in which lead has melted through a refractory horn to promote the dissolution of lead into the steel, and
This is a method for producing lead free-cutting steel, which is characterized by uniformizing the distribution of lead particles and free-cutting inclusions in the steel.

According to the present invention, the purpose of applying ultrasonic vibration is to promote the dissolution of lead particles and to uniformize the dispersion of lead in the steel. The position where the vibration is applied is not particularly limited, but is preferably at least one point between the mixing part and/or the melt qv part mentioned in b11, that is, the point where the lead particles are added and the position where the tundish nozzle is installed.

Further, as a means for applying ultrasonic vibration, any ultrasonic oscillation horn may be an immersion type refractory horn made of an appropriate refractory material such as alumina or magnesia. By using such a refractory horn as an immersion type, lead dissolution and uniform precipitation are promoted. The installation location of the immersion type refractory horn is preferably in the vicinity directly below the addition point of lead particles and in the vicinity directly above the tundish nozzle, thus applying ultrasonic vibration to the mixing section and/or molten steel section as described above. can be added.

Note that the structure and other details of the ultrasonic oscillation horn are already clear to those skilled in the art from the above description, and no further explanation is necessary.

The invention will now be further explained with reference to the accompanying drawings.

FIG. 1 schematically shows a method for manufacturing lead free-cutting steel by continuous casting according to the present invention. Molten steel contained in a ladle 1 is supplied to a tundish 3 through an immersion nozzle 2. and then injected into the mold 5 from the dandy nozzle 4. Lead particles (preferably about 0.5 m in diameter) are added to the molten steel 6 accommodated in the tundish 3 from the copper particle input lower at a position intermediate between the immersion nozzle 2 and the tundish nozzle 4 as shown by the arrow in the figure. (fine particles) are added.

In the illustrated example, refractory horns 8 for applying ultrasonic waves are provided near the addition point of lead particles and near the tundish nozzle m, respectively, by being immersed in the molten steel. This refractory horn 8 is connected to an ultrasonic transducer 10 via a metal horn 9, preferably made of titanium or steel. In this state, when ultrasonic vibrations are applied during melting and lead particles are added, the addition of ultrasonic vibrations can prevent gravitational segregation due to the difference in specific gravity between molten steel and lead inside the tundish, and melt into the steel. It is possible to improve the lead yield.

Here, the length of each of the metal horn and refractory horn is 2 people, tB is the ultrasonic wavelength in the horn, respectively,
If λ and λB are satisfied, the vibration displacement at the tip of the refractory horn can be maximized by satisfying tk=---2. An example of how the horn is attached at this time is schematically shown in FIG. 2 together with the vibration displacement distribution. In the figure, the ultrasonic vibrator 10 and the metal horn 9 are screwed together, and the metal horn 9 and the refractory horn 8 are crimped using a jig 11.

When each horn has the above length, the vibration displacement distribution in the horn will be as shown in the figure, and as can be seen from these,
It is possible to give the maximum vibration m displacement to the tip of the horn. -1
However, as shown in Figure 1, by applying ultrasonic vibrations not only to the point where lead particles are added but also to the point directly above the tundish nozzle, the dispersion of lead into the steel within the tundish can be made more uniform. can be converted into

When ultrasonic vibration was applied using the method of the present invention using an ultrasonic vibrator with an oscillation output of 400 W, the solubility of lead particles in molten steel was 0.13% compared to the conventional case in which no ultrasonic waves were applied.
% improved. As described above, the present invention can improve the solubility, uniformize the precipitation of free-cutting inclusions, and produce excellent lead free-cutting steel.

Examples of the method of the present invention are shown below, but are merely for illustrating the present invention and are not intended to limit the invention.

EXAMPLE A slab was tested for casting using an apparatus similar to that shown in FIG. 1. At that time, ultrasonic vibration was applied under the casting conditions shown in Table 1 at -Aoi 2.

The results are summarized in Table 3. As can be seen from these results, compared to when no ultrasonic vibration is applied, adding ultrasonic imaging increases the dissolution rate of lead into steel, improves the yield, and improves the dissolution rate of lead into steel. The homogeneity of the slab was improved due to better uniformity of dispersion.

Table 1 Casting conditions (weight %) Slab size: 400+omX300mm Casting speed: 0.
6? PI/1lth Lead added! ::0.35% Lead addition rate: 4Kg/sds Lead addition position: 500m before the tundish dripping part Ultrasonic vibration frequency: 18 kHz Ultrasonic output: 400W/1 unit Ultrasonic addition position: 1 lead gradual addition position , and two ultrasonic horns in total between the lead addition position and directly above the strand (directly above the mold) Material and shape: Metal horn (material: titanium) 25m + φ (diameter) x 1
40 pieces (length) ・Refractory horn (material: alumina) 25m + φ (@diameter) X 3405w + (length)

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing how ultrasonic vibration is applied when manufacturing lead free-cutting steel by continuous casting according to the present invention; and FIG. 2 is an example of how an ultrasonic vibrator and horn are attached. FIG. 1... Ladle, 2... Immersion nozzle, 3... Tundish nozzle, 4... Tandish nozzle, 5... tA
"ls 6...molten steel, 7...lead particle inlet, 8.
... Refractory horn, 9... Metal horn, 10... Ultrasonic vibrator. Applicant's agent Patent attorney Akira Hirose -O/Zatatsumi 2

Claims (1)

[Claims] In a method for manufacturing lead free-cutting steel by adding fine particles of lead to molten steel in a tundish in continuous casting and dissolving the lead in the molten steel, the mixed part of molten steel and lead particles and/or
Alternatively, ultrasonic vibrations are applied to the molten steel part in which lead has melted through a refractory horn to promote the dissolution of lead into the steel and to reduce the distribution of lead particles and free-cutting inclusions in the steel. A method for manufacturing lead free-cutting steel that is characterized by uniformity.