RU2369643C1 - Method of producing sorbitized high-duty rod - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to iron and steel metallurgy, particularly to production of rod out of high carbon steel designed for further processing into wire used in cables and hoses of high pressure. The method consists in metal melting, in tapping metal into a casting ladle, in reducing steel in the casting ladle, in out-of-furnace treatment by chemical composition, in slag formation, in metal jet degassing with argon, in teeming metal at rate V=-0.028×C+1.82×A-0.028×T+42.34, where V is rate of teeming, m/min; C is carbon contents in metal before teeming, wt %; A is ratio of rod section sides, T is temperature of metal in an intermediary ladle, °C; 0.028; 1.82; 44.34 are empiric ratios obtained experimentally by determining effect of each parametre to rate of teeming; further the method consists in rolling a work piece to rod of required diametre; in cooling rod with water to temperature Tc.w.c=(δ₁₀+37.4×C-0.0632×d+4.247):0.06 where Tc.w.c is temperature of casting after water cooling, °C; δ₁₀ - is required specific elongation, %; C is contents of carbon in metal; wt %; d is diametre of rod, mm; 37.4; 0.0632; 0.06; 4.247 are empiric ratios obtained experimentally by determining effect of each parametre to specific elongation; then the process consists in air cooling.

EFFECT: implementation of method produces structure uniform in cross section and upgrades plastic properties of rod.

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Description

The invention relates to ferrous metallurgy, namely to the production of wire rod from high-carbon steel grades intended for further processing into wire for the manufacture of ropes and high pressure hoses.

A known method of producing steel for metal cord, including smelting in a steelmaking unit of an iron-carbon melt with a carbon content of not more than 0.20 wt.%, Releasing unrefined metal into a steel pouring ladle with a main lining and a porous plug for purging with argon, preliminary deoxidation of the melt when releasing carbon-containing in the ladle materials and ferromanganese, while the silicon-containing ferroalloys are added to the metal after metal evacuation, the slag-forming mixture is added to the ladle, and the vacuum carbohydrate deoxidation in a metal ladle to a carbon content within the steel grade, final adjustment of steel according to the chemical composition and temperature of the ladle furnace and continuous casting (RU, No. 2265064 C2, class C21C 5/54, published on November 27, 2005 .).

The disadvantage of this method is the contamination of the metal with non-metallic exogenous inclusions due to increased wear of the lining of the steel pouring ladle. Also, the scope of this technology is narrowed in the absence of a metal vacuum installation in the workshop.

The closest in technical essence and the achieved result is a method for producing wire rod from high-carbon steel of cord quality (RU, No. 2269579 C1, class C21C 7/00, published on 02/10/2006), including metal smelting, metal heating to 1600-1660 ° C and the release of metal from the furnace into the ladle with a carbon content of not more than 0.55 wt.% And sulfur 0.015 wt.%, While the content of colored impurities (Cr, Ni, Cu) and nitrogen is 0.04 wt.% And 0.004 wt.%. Prior to the release of the metal, the necessary amount of carbon-containing material is planted in the steel pouring ladle. When the metal is discharged from the furnace, slag-forming materials are placed in the steel pouring ladle, and after the ladle is filled with metal by half, ferroalloys are added based on the average value of the elements in the steel grade. Then, without downloading the slag, the metal is purged with argon for 5-8 minutes, after which the metal is treated on a ladle furnace with slag of variable basicity, moreover, 70-80% of the time the metal is kept under white highly basic slag, and 20-30% of the time - under the cover of low-base slag and purge the metal with argon through the bottom tuyeres. High-base slag is baked at the ladle furnace in the ratio CaO / CaF ₂ 3: 1 with a total amount of 6-7 kg / t and with a slag / metal ratio of 1.1-1.4 / 100, and slag is deoxidized with a coke mixture with a flow rate of 1.5-2.5 kg / t to obtain a basicity of B = 2.8-5.0. Induction of low-basic slag is carried out by adding silica sand with a SiO ₂ content _of at least 98% with a flow rate of 0.7-2.3 kg / t to obtain a basicity of B = 1.5-2.3. After that, the metal is purged with argon under such slag for 10-20 minutes without exposing the metal mirror in the region of the purging spots with a flow rate of 30-125 liters per minute. After out-of-furnace treatment of steel, it is casted on a continuous casting machine at a speed of 1.8-2.4 m / min per section of the mold 125 × 125, where the metal stream is protected in the steel casting ladle-intermediate ladle section using a submersible refractory pipe with feed in the cavity of the argon pipe, while the temperature of the metal in the intermediate ladle is 1515-1525 ° C. Then, the obtained continuously cast billet is rolled to obtain a wire rod of the required diameter using water and air post-deformation cooling.

The known method does not achieve the required technical result for the following reasons.

The known method does not provide the required standard combination of complex strength (σ _in and σ _t ) and plastic (δ ₅ ) properties of the finished product, because it does not take into account the influence of deviations of the chemical composition of steel within the grade.

A wire rod obtained in a known manner is characterized by insufficient plastic properties, which leads to increased breakage of the wire rod. This is due to the fact that, at a high casting speed, the crystallization rate of the obtained continuously cast billet with a small square section is high enough, which leads to the formation of a coarse dendritic structure and does not completely remove the axial segregation. Subsequent unregulated water post-deformation cooling in the presence of axial segregation and a coarse dendritic structure does not allow to obtain a uniform cross-sectional structure, which negatively affects the plastic properties of the resulting wire rod, which impede the drawing process to the specified cord cord sizes and are accompanied by breaks in the drawing process.

The basis of the invention is the task of improving the method for producing sorbitized wire rod for critical purposes by optimizing process parameters. The expected technical result is a decrease in the content of non-metallic inclusions by ensuring the optimal crystallization rate of the continuously cast billet, which leads to a uniform cross-sectional structure and provides an increase in the plastic properties of the wire rod.

The problem is solved in that in a method for producing a sorbitized wire rod for critical purposes, including metal smelting, metal discharge into a steel pouring ladle, metal deoxidation in a steel pouring ladle, out-of-furnace treatment in chemical composition, slag induction, argon purge of metal, metal casting, rolling of continuously cast billet to of obtaining a wire rod of the required diameter using water and air post-deformation cooling, according to the invention, the metal is cast at a speed Anna from the ratio:

V = -0.028 × C + 1.82 × A-0.028 × T + 42.34,

where V is the casting speed, m / min;

C is the carbon content in the metal before casting, wt.%;

A is the aspect ratio of the cross section of the workpiece;

T is the temperature of the metal in the intermediate ladle, ° C;

0.028; 1.82; 44.34 - empirical coefficients obtained experimentally to determine the influence of each parameter on the casting speed,

and post-deformation water cooling of the wire rod is carried out to a metal temperature, determined from the dependence:

Mp = (δ ₁₀ + 37.4 × C-0.0632 × d + 4.247): 0.06,

where Tv.o - metal temperature after water cooling, ° С;

δ ₁₀ - the required elongation,%;

C is the carbon content in the metal, wt.%;

d is the diameter of the wire rod, mm;

37.4; 0.0632; 0.06; 4.247 - empirical coefficients obtained experimentally to determine the effect of each parameter on elongation.

The essence of the proposed technical solution is to select the speed of metal casting depending on the cross section of the continuously cast billet, the temperature of the metal in the intermediate ladle and the carbon content before casting, rolling the continuously cast billet with regulated water cooling to the required diameter of the wire rod based on the required elongation.

The casting of metal at a speed of the proposed dependence allows to obtain a continuously cast billet of the required quality with a minimum content and size of non-metallic inclusions due to the formation of a dendritic macrostructure with dendrites of a certain size and minimal axial segregation.

The process of obtaining a critical rod is to ensure its necessary plastic properties due to regulated water cooling, which allows to obtain a uniform cross-section of the structure of supercooled austenite, and then the use of intensive air cooling with the help of fans on the air-cooling conveyor results in a sorbitol-like structure close to eutectoid.

Example

Responsible sorbitized wire rod was prepared as follows. The intermediate was smelted in a steelmaking unit and, at a content of 0.05 wt.% Carbon, was discharged into a 200-ton steel-pouring ladle. Before releasing the metal, 650 kg of carbon-containing material were planted in the steel pouring ladle at its bottom. In the process of metal release, slag-forming, 1100 kg of ferromanganese and 780 kg of ferrosilicon were planted in the bucket. The metal was purged with argon. When the first portions of furnace slag appeared on the trench, the argon supply was stopped and the slag was cut off. After the metal was released, the metal bucket was transferred to the ladle furnace installation. At the ladle furnace, the metal was averaged with argon at a flow rate of 625 l / min for 3 minutes, then the metal temperature was measured and a sample was taken to determine the chemical composition of the metal. The chemical composition of the metal is as follows, wt.%: 0.63 carbon, 0.16 silicon, 0.46 manganese, 0.017 sulfur and 0.007 phosphorus, the temperature of the metal was 1524 ° C.

During the purge, the chemical composition of the steel was adjusted by additives of ferroalloys and the rest of the carbon-containing material in the form of a flux-cored wire.

After obtaining the necessary parameters: metal temperature 1524 ° C, the required chemical composition, wt.%: 0.827 carbon, 0.29 silicon, 0.56 manganese, 0.005 sulfur and 0.008 phosphorus, the metal was transferred to a continuous casting machine. After installing the bucket on the stand, the intermediate bucket was filled with metal, and the metal temperature was measured, which amounted to 1500 ° C. The casting was carried out on a 5-strand continuous steel casting machine, on the mold section 150 × 150 at a speed selected from the proposed dependence:

V = -0.028 × 0.827 + 1.82 × 1-0.028 × 1500 + 42.34 = 2.1 m / min.

After casting and cutting metal, workpieces with a length of 11,700 mm were placed into cooling boxes, where they cooled to 100 ° C. Then, samples (templates) were taken from the middle blanks for each stream to assess the macrostructure. If the macrostructure corresponded to the requirements of normative documentation, they were shipped to the varietal workshop.

After inspection of continuously cast billets and sorting of billets with existing surface defects, they were transferred to loading tables of a fine-grained wire mill. Billets with a cross section of 150 × 150 mm were placed in a walking-hearth heating furnace, where they were heated for two hours. After heating the billets, they were fed to a rolling mill, where, according to the order, a rolled wire of 6.5 mm diameter was rolled with the required elongation of at least 10% for steel with a carbon content of 0.80-0.85 wt.%. The rolling was carried out according to the following mode: the temperature of the onset of rolling was 1050 ° С, the total degree of deformation was 680, interdeformational cooling to a temperature of 850-890 ° С before the finishing group, rolling in the finishing group, the speed of the end of rolling was 79 m / s. After rolling, the wire rod was intensively cooled in a water cooling line. The time between the end of rolling and the start of cooling was 0.024 s. Water cooling was carried out in two boxes equipped with six nozzles each, to a metal temperature determined by the proposed dependence:

Melting point = (10 + 37.4 × 0.827-0.0632 × 6.5 + 4.247): 0.06 = 745 ° C.

Next, the rolled products were stacked with a coil former on an air-cooled conveyor. After laying, the temperature of the wire rod was fixed, which was 750 ° C, then the wire rod was subjected to air cooling using 14 fans to a temperature of 400 ° C with a cooling rate of 3.5-4.5 ° C / s. After the air-cooled conveyor, the decomposed turns were collected in a riot, the mass of which was 2000 kg.

Then, wire rod samples were taken, tests were carried out, the following properties were obtained: temporary resistance (σ _B ) 1190 N / mm ² , elongation (δ ₁₀ ) 13%.

The wire rod obtained by the proposed method is characterized by higher plastic properties compared to the wire rod obtained in a known manner - the closest analogue. Subsequently, during drawing, in the presence of higher values of relative elongation, a higher total degree of compression during cold deformation is provided, which reduces or eliminates the number of times the expensive patenting process is used.

Thus, the use of the proposed method allows you to master the production of wire rod for critical purposes with the required plastic properties, improves the quality and manufacturability of wire rod production, as well as its further processing at all stages with minimized costs.

Claims (1)

A method of producing a sorbitized wire rod, including metal smelting, metal pouring into a steel pouring ladle, metal deoxidation in a steel pouring ladle, out-of-furnace treatment by chemical composition, slag induction, metal purging with argon, metal casting, rolling of a continuously cast billet to obtain a wire rod of the required diameter using water and air and air post-deformation cooling, characterized in that the metal is cast at a speed selected from the ratio
V = -0.028 · C + 1.82 · A-0.028 · T + 42.34,
where V is the casting speed, m / min;
C is the carbon content in the metal before casting, wt.%;
A is the aspect ratio of the cross section of the workpiece;
T is the temperature of the metal in the intermediate ladle, ° C;
0.028; 1.82; 42.34 - empirical coefficients obtained experimentally to determine the influence of each parameter on the casting speed, and post-deformation water cooling of the wire rod is carried out to a metal temperature, determined from the dependence
T.v.o = (δ ₁₀ + 37.4 · C-0.0632 · d + 4.247): 0.06,
where t.v.o. - metal temperature after water cooling, ° C;
δ ₁₀ - the required elongation,%;
C is the carbon content in the metal, wt.%;
d is the diameter of the wire rod, mm;
37.4; 0.0632; 0.06; 4.247 - empirical coefficients obtained experimentally to determine the effect of each parameter on elongation.