RU2430977C1 - Procedure for heating blanks at section and wire mills - Google Patents

Abstract

FIELD: metallurgy. ^ SUBSTANCE: blank is preliminary heated in heating furnaces to temperature of 800-850C and cleaned from scale at given temperature. Further, it is heated to temperature of rolling in a heating installation by conductive and/or inductive procedure. Also, the said installation, roller-bed transporting blank to it and roller-bed transporting blank to a roughing train are covered with heat insulated jacket filled with protective gas. ^ EFFECT: reduced exhaust of harmful substances, reduced scale formation, increased quality of section iron, facilitation of uniform blank heating by length and cross section. ^ 1 ex, 1 dwg

Description

The invention relates to ferrous metallurgy, and in particular to methods of heating billets of steels of various chemical composition on varietal and wire mills.

There is a known method of heating billets on high-quality and wire mills, including heating the billets in heating furnaces to the rolling temperature, cleaning the hot billets from scale by hydraulic breakdown and further rolling on the respective mills (Danieli News Issue No. 136. December 2003, p. 18).

The disadvantages of this method are the loss of metal with waste and furnace scale and the uneven heating of the workpiece along the length and cross section.

The closest analogue to the claimed method is a method of heating billets, including heating the billets in heating furnaces to temperatures of 900-1150 ° C, removing scale, heating the inductor to the rolling temperature and further rolling, described in the article "Application of induction heating in the metallurgical industry". Author: V. B. Demidovich (www.estel.ee/estel/document.php?id=10).

The disadvantages of this method are the unjustified overheating of workpieces to temperatures of 900-1150 ° C, as a result, the large total energy costs and losses of metal with fumes and furnace scale, intense scale formation, as a result, increased wear of the rolls and wire fittings, uneven heating of the workpiece along the length and section. In addition, it is not possible to return the workpiece back to the furnace before feeding the workpiece to the inductor in the event of an emergency stop of the mill, which significantly increases rejects due to cooling of the workpieces before entering the mill and the forced discharge of the workpieces.

The technical problems solved by the invention are as follows:

- the exception of the release of billets in the event of an emergency stop of rolling mills, since the billets are intensively heated immediately in front of the mill;

- a significant reduction in gas consumption, as a result, a reduction in emissions of harmful substances (combustion products);

- reduction of the temperature of the atmosphere in the furnace, as a result, an increase in the service life of refractories

- high heating rates (short time and high productivity);

- operational process control due to less equipment inertia;

- less scale formation and, as a result, better finished product quality, less wear on rolls and wire fittings;

- high quality of heating (uniformity in length and cross section) due to internal heating.

The problem is solved in that in the method of heating billets on high-quality and wire mills, including heating the billet in heating furnaces, cleaning the billet from scale, heating it by induction, in contrast to the closest analogue, heating the billet in heating furnaces is carried out to a temperature of 800-850 ° C, then the workpiece is cleaned of scale at a given temperature, then it is heated by the conductive and / or induction method to the rolling temperature, and the installation is heated by conductive and / or ind The method of rolling and live rolls: leading the blank to it and leading the blank to the roughing group of stands, are covered by a heat-insulated casing, in addition, the casing is filled with protective gas.

The essence of the proposed technical solution is as follows.

When the billet is heated in a heating furnace to 800-850 ° C, less scale formation occurs, while heating to these temperatures is more efficient in a flame manner.

Induction and / or conduction heating can increase the heating rate of the metal and reduce the inertia of the heating section, while the protective atmosphere prevents the formation of scale on the workpieces, thereby reducing the consumption coefficients of the final product.

The insulated (lined) protective casing minimizes heat loss to the atomosphere in the area from the heating furnace to the mill roughing stands.

Before the workpiece is fed into the conduction and / or induction heating installation, it remains possible to return the workpiece back to the furnace in the event of an emergency stop of the mill, which significantly reduces metal rejection due to cooling of the workpieces before entering the mill and forced discharge of the workpieces. Between the stripping and before the workpiece is dispensed from the heating device, the workpiece can be in a protective atmosphere (for example, nitrogen), which virtually eliminates the oxidation of metal in this area. Shielding gas is supplied directly to the insulated casing and the conductive and / or induction heating device.

The implementation of the proposed method is illustrated in the drawing, where 1 is a heating furnace; 2 - a device for cleaning workpieces from scale; 3 - heated above the Curie point and peeled workpiece; 4 - insulated casing; 5 - a device of conductive and / or induction heating; 6 - workpiece heated to rolling temperature; 7 - draft mill stand.

An example of a specific implementation of the method.

High-quality billets with dimensions of 150 × 150 × 12000 mm are fed into a heating furnace, for example, of a flame type, where they are heated to a temperature of ~ 800 ° C, which slightly exceeds the Curie point (768 ° C for pure iron). This allows you to get rid of the intense oxidation of the metal in the furnace and virtually eliminate furnace scale and fumes. A billet with a temperature of 800 ° C from the furnace is fed to the delivery roller and mechanically cleaned, for example, with rotating brushes or with a metal scraper, which helps to get rid of the scale formed after continuous casting machines. After mechanical cleaning, the workpiece is non-stop along the rolling table covered by a heat-insulated casing (metal frame, lined with heat-insulating material inside) is fed into the conductive and / or induction heating unit of the workpieces, where it is heated to a rolling temperature, for example, to 1150 ° C, then the workpiece is fed through the live roll to roughing group of stands. The choice of frequency during conductive and / or induction heating varies depending on the grade of steel, the initial and required final temperature of the workpiece. In the case of induction heating for a workpiece with a cross section of 150 × 150, the frequency is 0.05 ÷ 1 kHz. Installation of heating by the conductive and / or induction method and live rolls: leading the workpiece to it and leading the workpiece to the roughing group of stands are covered with a heat-insulated casing made of a metal frame inside lined with heat-insulating material. Shielding gas, such as nitrogen, is supplied directly to the insulated jacket.

Claims (1)

A method of heating billets on high-quality and wire mills, including heating the billet in heating furnaces, cleaning the billet from scale and heating the billet after cleaning, characterized in that the billet is heated in heating furnaces to a temperature of 800 ÷ 850 ° C, then the billet is cleaned from scale at a given temperature, then it is heated to a rolling temperature in a heating installation using a conductive and / or induction method, said heating installation, a roller table leading the workpiece to it, and gang, to feed the workpiece roughing stands, harboring insulated casing which is filled with protective gas.

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