RU1787663C - Method and apparatus for treating metal with gas during rising pouring - Google Patents

Abstract

Using; an inert or neutral gas is introduced into the center gas before the metal begins to flow under excess pressure, and during the casting period the pressure is increased at a rate of 0.20-0.50 atm / min and the gas supply is stopped after the casting is completed. The device for carrying out the method comprises a housing 1. and an annular cavity 2 in communication with a pipe 3 for supplying gas from the network and a gas supply hole and a central one made in the form of a slot channel 4 formed by two conical cylinders 5 and b inside the cone. The device is equipped with a receiving refractory funnel 7 and is installed on a gas tight seal 8 located on the upper base of the center 9. 2 s. n, f-ly. 1 ill., 3 tablets

Description

FIELD: metallurgy, in particular, metal siphon casting in g.

The purpose of the invention is to improve the surface quality of the ingot, improve its macrostructure and reduce gas consumption.

The drawing shows a device; general form. 3 ..... ::

The device comprises a housing 1 in the form of a hollow cylinder, an annular cavity 2, communicating with a pipe 3 for supplying gas from the network and an outlet for supplying gas to the center, made inside the housing in the form of a slit-like channel 4 formed by the walls of the cones 5 and 6 inserted one into another In addition, it is equipped with a receiving refractory funnel 7. The device is mounted on a gas tight seal 8 located on the upper base of the center 9.

Example. The experiments were carried out under industrial conditions when casting steel grades 20, 15KhF, 12-20KhNZA. ZOKHGSA, ZOKHGSN2A, ShKh15, 65G and others into ingots weighing 2.7; 3.6 and 4.8 tons. Using the proposed device, they poured .14 bushes - swimming trunks (bush - 4 molds) into ingots of the indicated weights, if the casting was carried out on several pallets. For comparison, 20 bushes - melting of similar steel grades spilled using a prototype device.

Before casting steel, a layer of refractory mass, asbestos cord or high-alumina felt with a thickness of 10-20 mm was laid on the upper base of the center, and then the proposed device was installed using a crane on a gas-tight seal. The connection of the device’s nozzle to the argon line was carried out with a flexible sleeve with a quick-disconnect connection. After that, a metal cover was placed on the upper base of the receiving funnel of the device, 5-10 minutes before the start of metal casting, argon was introduced into the center under an overpressure of 0.02 MPa. The duration of the introduction of argon into the center was determined depending on the volume of the working space of the molds and the gate system. In argon ingots weighing 2.7 tons, argon was introduced for 5 minutes, and for ingots weighing 4.8 for 10 minutes. Before casting, the metal cover was removed from the hopper of the device. During the casting of the metal, the argon overpressure was increased at a rate of from 0.01 to 0.060 MPa / min.

The width of the slit-like channel of the gas supply device during casting was in the optimal range (3-5

mm) The conical cylinder 6 was attached to the device casing by welding.

After the casting of the experimental mold bush was completed, the supply of argo was stopped. on and the device was disconnected from the gas pipeline. The device was removed from the center and preparations were made for the next melt.

The metal was controlled in accordance with the requirements of GOST and TU for each steel grade. Additionally, the surface quality of the ingots was visually evaluated, the depth of shrinkage defects in the profitable part of the ingots, the gas content and the mechanical properties of the deformed metal in the temperature range of hot deformation were determined.

A comparative analysis of the results of the study of steel, cast by the proposed method and the method specified in the prototype, revealed significant advantages as an experimental metal. The number and depth of defects on the surface of ingots spilled decreased

with argon treatment using the proposed device. Metal rejection during rolling of experimental melts averaged 0.3% against 1.0% in comparative melts. The number of blooms of I category of Surface quality increased from 47 (comparative melts) to 64.6% (experimental melts), and of the III quality category decreased from 16.5 to 10.4%, respectively. The concentration of gases in steel has noticeably decreased

20KhGNTR brands (see Table 1), and the number of revolutions increased twofold when twisting the samples in the temperature range. 1000-1 T50 ° C compared with steel cast according to the method of the prototype.

. Processing by the proposed method allowed to significantly reduce the contamination of the metal with non-metallic inclusions. Thus, the maximum (numerators) and average (denominators) scores for assessing the contamination of steel of the ZOKHGSA grade are given in table. 2.

By metallographic analysis of the surface of the rolled products obtained from ingots of experimental and comparative melts, it was found that the metal treatment with argon by the proposed method reduces the number and depth of surface defects.

Mechanical properties of cast steel

according to two technology options at 20 ° C they met the requirements of GOST for controlled grades of steel and practically did not differ. At the same time, the depth of occurrence of shrinkage defects in the profitable part of the ingots decreased by 0.6–2%, depending on the steel grade.

In the table. Table 3 summarizes the consumption of argon and rolling of open-hearth and steel, cast according to two technology options, into ingots weighing 4.8 tons. Comparing the data in Table. 3, it can be concluded that the proposed casting method allows reducing the argon consumption necessary for metal processing by the prototype method by two and more times and significantly improving the quality of billets obtained by rolling ingots.

At the same time, a decrease in the argon feed rate to the proposed device to values less than 0.020 MPa / min, or its increase to values greater than 0.050 MPa / min, significantly reduces the processing effect: an increase in metal reject during rolling of ingots is observed and the quality of the rolled surface deteriorates (see tab. 3). The optimal limits for the argon feed rate to the device of the invention are 0.20-0.50 MPa / min.

SUMMARY OF THE INVENTION

1. A method of treating metal with gas during siphon casting, which includes starting the supply of inert or neutral gas to a center gas before pouring into it a melt of inert or neutral gas under atmospheric pressure, pouring the melt into the center gas and ending the gas supply, heating and c in that, in order to improve the surface quality of the ingot, improve its macrostructure and reduce gas consumption, the gas is supplied during the melt pouring period with an increase in pressure, the increase being carried out at a rate of 0.20-0.50 atm / min;

2. A device for processing metal by gas during siphon casting, comprising a center, hollow cylinder body, an annular cavity in communication with a pipe for supplying gas from the network and an outlet for supplying gas to the center, characterized in that, in order to improve surface quality ingot, to improve its macrostructure and reduce gas consumption, it is equipped with a gas permeable seal located on the upper base of the center, and a receiving funnel located in the upper part of the housing, and a hole for supplying gas made inside the body in the form of a slit-like channel with a width of 3.0-5.0 mm, formed by the walls of the cones inserted one into the other.

Table 1

thirty

table 2

Table 3 The results of metal processing with argon during casting steel into ingots weighing t, 8 t

Processing method Increase rate Rejection within the limits of the wilam Cleanliness surface Argon consumption by gas and constructional excess pressure of defects,% of rolled metal by processing category.

Note. For breaks of the 1st category of quality, the surface area of the workpiece subjected to stripping did not exceed 15 of the total burnt, And the quality category was 25%.