RU2343209C2 - Wire for alloying of liquid steel by boron - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: in wire relation between boron content in powder filler and powder filler content in wire is a value (0.18-0.40):1, and relation between wire components is established as following, wt %: powder filler, containing boron 65-80, metal envelope 20-35. In the capacity of powder filler, containing boron, can be used alloy of boron with iron, at that boron content in alloy is 15-25 wt %.

EFFECT: increasing and stabilisation at high level of boron recovery range, decreasing of processing scrap, reduction of wire consumption and effectiveness increase of boron usage.

2 cl

Description

The invention relates to ferrous metallurgy, and in particular to out-of-furnace treatment of metallurgical melts with powdered reagents.

The closest in technical essence and the achieved effect to the claimed is a wire for alloying steel with boron, consisting of a metal sheath and a powder filler containing boron. The filling of the wire is 320 g / m (Dyudkin D.A., Kisilenko V.V., Onishchuk V.P. and others. Mastering the technology of out-of-furnace processing of various groups of steel grades with boron-containing flux-cored wire at RUE “BMZ” // Proceedings of the Eighth Congress of Steelmakers (Nizhny Tagil, October 18-22, 2004) - Moscow. - Chermetinformatsiya OJSC. - 2005. - S.407-411). This wire is selected as a prototype. The introduction of boron into molten steel in the form of a wire allows one to reduce waste and achieve an increased level of boron assimilation in comparison with the use of bulk materials, but still the average level of boron assimilation from a wire remains unstable - for steel 20KHNR - 81% (from 68 to 100%) , on cord steel grades - 68% (from 59 to 76%). This is due to the fact that the ratio between the components is not determined in the wire, which does not make it possible to stably provide the necessary stiffness of the wire for entering it to a sufficient depth so that the maximum volume of metal in the ladle is captured by the reaction of boron with the melt, which leads to unstable results when using wire, increased costs and reduced efficiency of the process of alloying liquid steel with boron.

The basis of the invention is the task of improving the flux-cored wire for alloying molten steel with boron by setting certain limits for the ratio between the individual components of the wire between themselves and the entire wire as a whole. The solution to this problem makes it possible to stably provide the necessary stiffness of the wire for its introduction to a sufficient depth, to melt and release the powder filler, to cover the maximum volume of metal in the ladle by the reaction of the interaction of boron with the melt, to synchronize in time the processes of boron release into the melt and heating of the powder filler to the ambient temperature metal, which will significantly accelerate the process of dissolution of boron in steel. This allows you to increase and stabilize at a high level the degree of assimilation of boron, reduce technological marriage, reduce wire consumption and increase the efficiency of use of boron.

The essence of the invention is that in a wire for alloying liquid steel with boron, consisting of a metal sheath and a powder filler containing boron, the ratio between the content of boron in the powder filler and the content of powder filler in the wire is (0.18 ... 0.40) : 1, and the ratio between the components of the wire is set as follows, wt.%:

boron-containing powder filler 65 ... 80 metal shell 20 ... 35

As a powder filler containing boron, an alloy of boron with iron can be used, and the boron content in the alloy is 15 ... 25 wt.%.

The essential features common with the prototype are:

- metal shell;

- powder filler containing boron.

Distinctive features of the prototype essential features are:

- the ratio between the boron content in the powder filler and the content of the powder filler in the wire is (0.18 ... 0.40): 1;

- the ratio between the components of the wire is set as follows, wt.%:

boron-containing powder filler 65 ... 80 metal shell 20 ... 35

An additional significant feature is:

- as a powder filler containing boron, an alloy of boron with iron is used, and the boron content in the alloy is 15 ... 25 wt.%.

The above features are necessary and sufficient for all cases to which the scope of the invention applies.

There is a causal relationship between the essential features and the technical result — an increase and stabilization at a high level of the degree of assimilation of boron, a decrease in technological rejects, a decrease in wire consumption and an increase in the efficiency of use of boron, which is explained as follows. A wire with the specified limits of the ratio between the components is steadily immersed in a bucket of liquid steel to a sufficient depth. In the local zone of interaction with the melt, the metal shell melts, the powder filler is released and the boron begins to dissolve in the volume of liquid steel, increasing the content to the required value of chemical analysis of a given steel grade. The indicated ratio between the boron content in the powder filler and the content of powder filler in the wire in the range (0.18 ... 0.40): 1 allows you to synchronize in time the processes of boron release into the melt and heating of the powder filler to the temperature of the surrounding metal, which significantly accelerates the dissolution process boron in steel. The indicated ratio between the powder filler containing boron and the metal sheath (65 ... 80) :( 20 ... 35) wt.% Stably provides the necessary wire stiffness for entering it to a sufficient depth so that the maximum volume of metal is covered by the reaction of boron with the melt the bucket. The process of treating liquid steel with wire with all the specified parameters proceeds quietly, without emissions and sparging. All this allows you to significantly increase the degree of assimilation of boron, reducing its fumes. The ratio between the boron content in the powder filler and the content of powder filler in the wire within the specified limits is due to the fact that if it is less than 0.18: 1, the powder filler will be released into the melt with a temperature lower than that of the surrounding metal, and there will be additional losses heating and dissolving boron-containing material, lowering the temperature of the steel in the ladle and, as a result, lowering the efficiency of boron use. If the indicated ratio is more than 0.40: 1, this will lead to the manufacture of a wire with a thin sheath and, when used, the sheath will melt to an insufficient depth, the powder filler will be released into the melt and the boron will dissolve in the upper layers of the metal, which will lead to reduce the degree of assimilation of boron and, as a result, reduce the efficiency of use of boron, increased consumption of wire. Failure to comply with the specified ratio between the components of the wire will not make it possible to stably provide the necessary stiffness of the wire for its introduction to a sufficient depth and will lead to separate local zones of the melt not covered by the reaction of interaction with boron or, conversely, a supersaturated boron, which will significantly reduce the efficiency of wire use the second case will lead to increased burnout and will not give the opportunity to consistently receive a high level of its assimilation. As a powder filler containing boron, an alloy of boron with iron can be used, and the boron content in the alloy is 15 ... 25 wt.%.

The analysis showed that the claimed invention has a novelty and inventive step, and it is the specified set of essential features that provides a technical result - increasing and stabilizing at a high level of boron assimilation, reducing technological marriage, reducing wire consumption and increasing boron utilization efficiency.

A flux-cored wire is made as follows. The metal strip is profiled into a groove-like sheath. Dosed portions from the hopper fill the shell with powder containing boron, which is evenly distributed over the gutter of the shell. Then, with the help of roller stands, they compress the shell and form a lock. The finished wire is wound on coils and delivered to the steel processing department.

At one of the metallurgical enterprises in the steel mill tested the proposed wire. Steel 20KHNR is smelted in an electric arc furnace (boron content limits are 0.001 ... 0.005%), released into a 100-ton bucket and transferred to an out-of-furnace treatment plant equipped with wire feeders, where deoxidation, averaging blowing and other necessary technological operations are carried out. Then a metal sample is taken, the content of boron in the metal is determined, and the amount of boron that must be introduced into the bucket in the form of a flux-cored wire is calculated. After this, a flux-cored wire of ⌀ 13 mm is introduced into a sheath made of 08Yu steel with ferroboron filling (17% boron). The filling of the wire along the ferroboron is 500 g / m, along the boron - 85 g / m. The ratio between the powder filler containing boron and the metal shell was 74:26 wt.%, The ratio between the content of boron in the powder filler and the content of powder filler in the wire is 0.23: 1. Introduce 30 m of wire (0.33 kg / t). Before the introduction of the wire, the boron content in the steel was 0.0002%. The increase in boron content in the finished metal was 0.00235%, and the boron content in the finished metal was 0.00237%. Conducted 20 treatments. The minimum degree of boron assimilation was 85.2%, the average - 92.1%, there was no technological defect.

At the same out-of-furnace metal processing unit, 20KhNR steel was treated with flux-cored wire filled with ferroboron (26% boron). The ⌀ 12 mm wire filling along the ferroboron was 300 g / m, along the boron - 78 g / m. The ratio between the powder filler containing boron and the metal shell was 62:38 wt.%, The ratio between the content of boron in the powder filler and the content of powder filler in the wire is 0.42: 1. The minimum degree of boron assimilation was 65.2%, the average - 72.1%, technological marriage - 1.6%. When the same amount of boron was added to the finished metal as in the inventive wire, the consumption of this wire was 42% higher.

Claims (2)

1. The wire for alloying liquid steel with boron, consisting of a metal shell and a powder filler containing boron, characterized in that the ratio between the content of boron in the powder filler and the content of powder filler in the wire is (0.18-0.40): 1, and the ratio between the components of the wire is set as follows, wt.%:
boron-containing powder filler 65-80 metal shell 20-35 2. The wire according to claim 1, characterized in that the boron-iron alloy is used as a powder filler containing boron, wherein the boron content in the alloy is 15-25 wt.%.