RU2803447C1 - Method for manufacturing clad steel sheet - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention is related in particular to a method for manufacturing a clad steel sheet by hot pack rolling. The method includes heating a bimetallic gas-filled package containing the main and cladding layers of sheet material arranged to form an interlayer space, and hot rolling the package. In the process of heating the package, a part of the inert gas is released from the interlayer space by means of a gas pressure equalization unit. During the first pass of hot rolling of the package, inert gas is released from the interlayer space of the package by means of a gas ejection unit, which contains at least one outlet channel that communicates with the interlayer space of the package and is covered with a steel plug made of steel of the same class as the steel from which it is made. the main layer of the package. The ratio of the working surface area of the steel plug S (mm²) to the smallest thickness h (mm) of its wall in the area of the working surface is S/h = 238–982.

EFFECT: preventing untimely destruction of the plug blocking the channel through which the inert gas is released from the package during the first rolling pass, while ensuring complete removal of the inert gas from the interlayer space of the package.

3 cl, 7 dwg, 2 tbl

Description

Field of technology

The invention relates to the field of metallurgy, namely to a method for producing clad steel sheets by hot batch rolling.

State of the art

Clad steel sheets are used in petrochemical and nuclear engineering and shipbuilding. The clad sheet combines the beneficial properties of its constituent materials, while the main layer of the clad sheet, usually made of pearlitic steel, is designed to withstand static and dynamic loads, and the cladding layer, usually made of high-alloy corrosion-resistant steel, protects the main layer from corrosive effects.

Batch hot rolling is a thermomechanical cladding method, which consists in the fact that a sealed welded package containing the main and cladding layers is heated to a temperature of 1000-1290°C and subjected to hot rolling on a plate mill. As a result of hot rolling, a metallic bond is formed between the contact surfaces of the layers.

The main differences in the known methods of batch rolling of sealed bimetallic stacks are in the individual elements of the stack design, as well as in the methods used to protect the contact surface of the layers from oxidation during the heating process for rolling (in particular, evacuation, filling with inert gases, the use of coatings).

One of the most important tasks in the production technology of clad hot-rolled sheets is the creation of a uniform, strong connection of layers over the entire area of their contact.

The closest method of the same purpose to the claimed invention in terms of the combination of characteristics is a method for manufacturing a clad steel sheet, including heating a bimetallic gas-filled package containing a main and cladding layers made of sheet metal, and hot rolling of the package. The gas-filled package used in this case is designed with the ability to release part of the inert gas from it, which is realized in the process of heating the package for rolling. In addition, the package used is configured to release inert gas from it, which is implemented in the first pass of hot rolling of the package through a device (process bar) attached to the package and containing an outlet channel covered with a membrane. Namely, when rolling the package in the first pass, the pressure of the inert gas breaks the membrane of the outlet channel and the inert gas is displaced by the metal package (see RF patent No. 195651, published 02/03/2020, adopted as a prototype).

The reasons preventing the achievement of the technical result indicated below when using the known method, adopted as a prototype, include the fact that the prior art does not disclose the features characterizing the material and geometric parameters of the membrane used, which covers the outlet channel of the technological strip, through which the inert gas is released into the first pass of hot rolling of the package. An incorrect choice of geometric parameters and membrane material can lead to its untimely rupture, which in turn will lead to the formation of discontinuities along the adhesion line of the main and cladding layers or local separations of the cladding layer along the perimeter of the manufactured steel sheet.

Disclosure of the Invention

The problem to be solved by the claimed invention is to develop a method for manufacturing a clad hot-rolled steel sheet that is free from the indicated disadvantages of the prototype and ensures the creation of a uniform, strong adhesion of the layers of the clad sheet over the entire area of their contact.

The technical result of the claimed invention is to prevent untimely destruction of the plug blocking the channel through which the inert gas is released from the package during the first pass of its hot rolling, and, accordingly, to increase the likelihood of complete removal of the inert gas from the interlayer space of the package during the first pass of it hot rolling.

The specified technical result when implementing the invention is achieved by the fact that in the method of manufacturing a clad steel sheet, including heating a bimetallic gas-filled package containing the main and cladding layers of sheet material, placed to form an interlayer space, and hot rolling of the package, a package with a at least one device including a gas pressure equalization unit and a gas ejection unit, or a package with at least one device containing a gas pressure equalization unit and at least one device containing a gas ejection unit attached to it. In this case, during the heating process of the package, a portion of the inert gas is released from the interlayer space of the package by means of a gas pressure equalization unit, which includes a channel communicating with the interlayer space of the package and containing a substance that prevents the free movement of the inert gas. When performing the first pass of hot rolling of the package, inert gas is released from the interlayer space of the package through a gas ejection unit, which contains at least one outlet channel communicating with the interlayer space of the package and covered with a steel plug. Moreover, they use a plug made of steel of the same class as the steel from which the main layer of the package is made, and the ratio of the working surface area of the steel plug S (in mm ² ) to the smallest thickness h (in mm) of its wall in the area of the working surface is S/ h = 238÷982.

In addition, private options for implementing the method are provided, according to which:

- as a substance that prevents the free movement of inert gas, electrocorundum granules with a fraction of 3÷120 microns are used;

- the plug and the main layer of the bag are made of pearlitic steel.

To prevent incomplete removal of inert gas from the interlayer space of the package during the first pass of hot rolling, it is necessary that, regardless of the volume of this gas, the ejection effect appears in a timely manner - when the inert gas sharply picks up speed through the cross section of the destroyed plug, sufficient to remove the entire volume of gas until the moment of shutdown a cladding layer of a channel made in the main layer and connecting the interlayer space with the device used for releasing gas. The ejection effect is achieved by the fact that, due to interatomic interaction, the gas medium, quickly moving through the section of the destroyed plug, must completely exit the interlayer space, forming a vacuum there at the moment the layers close on the specified channel. It is important that the ejection process proceeds faster than the gas extrusion process due to the closure of the interlayer space during the first compression of the package, since otherwise part of the gas will be hermetically locked in the interlayer space, which will lead to the formation of discontinuities along the adhesion line of the main and cladding layers.

In the claimed invention, the release of inert gas from the package is carried out in the first hot rolling pass through at least one device attached to the package and containing at least one outlet channel blocked by a steel plug. At the same time, the author of the invention has established that stable and timely ejection of inert gas during the first pass of hot rolling of the package is carried out when the condition S/h = 238÷982 is met, where S is the working surface area of the steel plug (in mm ² ), h is the smallest thickness walls of the steel plug in the area of its working surface (in mm).

The “working surface” of the plug wall should be understood as the surface of the plug wall, which, before its destruction during the first pass of hot rolling of the package, interacts with an inert gas and is limited by a contour corresponding to the minimum flow area of the outlet channel in the area of this plug.

When S/h is less than 238, during the first pass of hot rolling of the package, untimely (later) destruction of the steel plug blocking the outlet channel occurs. In this case, part of the inert gas is locked in the interlayer space of the package, and destruction of the weld seam connecting the layers of the package is also possible. Incomplete removal of inert gas from the interlayer space leads to the formation of discontinuities along the line of adhesion of the main and cladding layers, as well as to local separations of the cladding layer along the perimeter of the manufactured steel sheet.

When S/h is more than 982, during the first pass of hot rolling of the package, untimely (early) destruction of the steel plug blocking the outlet channel occurs, which causes the absence of the effect of ejection of inert gas and the locking of its part in the interlayer space of the package. In this case, there is also a high probability of destruction of the specified plug during the process of heating the package for rolling, which will lead to depressurization of the package. Negative consequences include the formation of discontinuities along the adhesion line of the main and cladding layers, as well as the formation of local separations of the cladding layer along the perimeter of the manufactured steel sheet.

The use of a plug made of steel of the same class as the steel from which the main layer of the package is made reduces the likelihood of deformation of the plug and depressurization of the package during its heating for rolling. Otherwise, due to different coefficients of thermal expansion of the material of the main layer and the material of the plug under conditions of its rigid fastening in the outlet channel, the plug will experience significant internal stresses.

The release of part of the inert gas from the package during its heating for rolling is carried out through the channel of a device attached to the package containing a substance that prevents the free movement of the gaseous medium. At the same time, the author of the invention experimentally established that the optimal operation of this device, ensuring the release of the necessary part of the expanding inert gas and preventing the entry of the external atmospheric environment into the interlayer space of the package, is carried out when using electrocorundum granules of fraction 3÷ as a substance that prevents the free movement of the gaseous environment 20 microns.

Brief description of drawings

The present invention is illustrated by drawings, where:

- figure 1 shows a general view of the bimetallic package;

- figure 2 shows a general view of the ejector body;

- Figure 3 shows a cross-section of a bimetallic package with an ejector body attached to it, made in the area of the gas ejection unit;

- figure 4 shows a cross-section of the ejector body in the area of the gas ejection unit (option);

- figure 5 shows a cross-section of the ejector body in the area of the gas pressure equalization unit, presented in general form;

- Figure 6 shows a cross-section of the ejector body in the area where the gas pressure equalization unit is located (version with two vertical channels);

- Figure 7 shows a cross-section of the ejector body in the area where the gas pressure equalization unit is located (version with one vertical channel).

Structural elements are indicated in the figures by the following positions:

1 - main layer;

2 - cladding layer;

3 - sealed weld;

4 - location area of the ejector body;

5 - surface on which the outlets of channels intended for communication with the external environment are located;

6 - surface on which a technological hole (or holes) is located, formed when creating a system of channels with a filler that prevents the free passage of a gaseous medium;

7 - surface on which the outputs of channels intended for communication with the interlayer space of the package are located;

8 - sealed weld;

9 - ejector body;

10 - steel plug;

11 - communication channel between the interlayer space of the package and the ejector body;

12 - sealed weld;

13 - channel through which inert gas enters the gas pressure equalization unit;

14 - a system of channels with a filler that prevents the free passage of the gas environment;

15 - communication channel between the gas pressure equalization unit and the external environment;

16 - sealing element;

17 - fixing element;

18 - filler that prevents the free passage of the gas environment.

Carrying out the invention

To implement the claimed method, a bimetallic gas-filled package is used, containing a main (1) and cladding (2) layers made of sheet material, connected by a sealed weld (3). A general view of the bimetallic gas-filled package is shown in Fig. 1.

As the initial workpiece for the main layer (1), in particular, a plate made of unalloyed or alloyed steel is used, and as the initial workpiece for the cladding layer (2), a sheet made, in particular, of high-alloy corrosion-resistant steel is used.

The bimetallic gas-filled package used is configured to release part of the inert gas from it during the process of heating the package for rolling. In addition, the bimetallic gas-filled package used is configured to release inert gas from it during the first hot rolling pass of this package.

The possibility of releasing part of the inert gas from the bimetallic gas-filled package during its heating for rolling is realized due to the gas pressure equalization unit.

The possibility of releasing inert gas from a bimetallic gas-filled package during the first pass of its hot rolling is realized due to the gas ejection unit.

The gas pressure equalization unit and the gas ejection unit can be made either in a single device (hereinafter referred to as the “ejector body”) or in separate devices.

In this case, the following versions of the bimetallic gas-filled package are possible:

- containing one or more ejector bodies;

- containing one or more devices, each of which has a gas ejection unit, and one or more devices, each of which has a gas pressure equalization unit.

The following describes in detail the design of the bimetallic package containing one ejector body.

The ejector body (9) is a steel product containing a system of channels. A general view of the ejector body (9) is shown in Fig.2. The most rational shape of the ejector body (9) is a parallelepiped, but another shape is also acceptable. On the surface (5) there are channel outlets (not shown in Fig. 2) intended to communicate the internal structure of the ejector body (9) with the external environment. On the surface (7) there are channel outlets (not shown in Fig. 2) intended to communicate the internal structure of the ejector body (9) with the interlayer space of the package. On the surface (6) there is a technological hole (or holes) (not shown in Fig. 2), formed during the manufacture of a system of channels (14) with a filler that prevents the free passage of the gaseous medium (shown in Figs. 5-7).

The ejector body (9) is attached to one of the ends of the main layer (1) of the bimetallic package in the area (4). The choice of the end of the main layer (1) of the package for placing the ejector body (9) on it depends on the direction of the first rolling pass of the package (see Fig. 1).

The cross-section of the bimetallic package with the ejector body (9) attached to it, made in the area of the gas ejection unit, is shown in Fig.3.

The ejector body (9) is attached to the end of the main layer (1) of the package with a sealed weld seam (8). The gas ejection unit communicates with the interlayer space of the package through a channel (11) made in the main layer (1). The outlet channel of the gas ejection unit is blocked by a steel plug (10).

During the first rolling pass of a heated bimetallic gas-filled package, inert gas from the space between the main (1) and cladding (2) layers enters under pressure through the channel (11) into the gas ejection unit, which leads to the destruction of the plug (10) and the release of gas through corresponding channel.

The gas ejection unit may have two or more outlet channels, each of which is closed with a separate steel plug.

The shape of the steel plug (10) can be different (in particular, round, oval, square, rectangular).

Figure 4 shows one of the possible mounting options for a steel plug (10), which in this case is placed inside the outlet channel of the ejector housing (9) and is secured by means of a sealed weld (12).

In accordance with the claimed invention, S/h = 238÷982, where S is the area of the working surface of the steel plug (in mm ² ), h is the smallest wall thickness of the steel plug in the area of its working surface (in mm).

The minimum flow area of the outlet channel in the area of the steel plug (10), shown in Fig. 4, is limited by a contour of diameter D. Thus, for this embodiment of the claimed invention where π is a mathematical constant (the number Pi, the rounded value of which is equal to 3.14), h is the smallest wall thickness of the steel plug in the area of its working surface, limited by a contour with diameter D (in mm).

Other methods of placing the steel plug (10) and its fastening are also acceptable, ensuring hermetically sealed closure of the outlet channel of the ejector body (9). In this case, for example, in the case of using a flat end plug, the minimum flow cross-section of the outlet channel will correspond to the cross-section of the outlet channel at the point where the plug adjoins its end.

The material for making the plug (10) can be pearlitic steel, for example, steel 09G2S.

Before rolling the bimetallic gas-filled package, it is heated in a furnace. When the bag is heated, the temperature of the inert gas located inside it rises, and, accordingly, its pressure increases. This necessitates the release of part of the inert gas from the package. The possibility of releasing part of the inert gas from the package during its heating is realized by means of a gas pressure equalization unit.

The gas pressure equalization unit can have various versions. Next, two possible options for such an implementation are disclosed.

Figure 5 shows a cross-section of the ejector body (9) in the area where the gas pressure equalization unit is located. The channel system (14) is shown in Fig. 5 in general form, as it can have several versions.

This unit includes a system of channels (14) containing a filler (18) (see Figs. 6, 7), which prevents the free passage of the gaseous medium. The filler (18) ensures the passage of inert gas through the channel system (14) only when the required excess gas pressure inside the package is reached.

The system of channels (14) on the one hand communicates with the channel (13), through which the inert gas enters the gas pressure equalization unit, and on the other hand, with the channel (15) connecting the gas pressure equalization unit with the external environment.

Figure 6 shows an embodiment of the channel system (14), which has two vertical channels, and Figure 7 shows an embodiment with one vertical channel. In this case, the operating principle of both options is the same and is as follows.

The gas pressure equalization unit communicates with the interlayer space of the bimetallic package. When a gas-filled package is heated in an oven, the temperature of the inert gas inside the package rises, which leads to an increase in gas pressure in the internal space of the package.

The filler (18) ensures the passage of inert gas through the channel system (14) only when the required excess pressure is reached. Inside the channel system (14), the filler is fixed by elements (17), which in particular are non-sealed screws or plugs. Using elements (16) (for example, steel plugs), the process holes are sealed, for which, for example, welding can be used.

Electrocorundum can be used as a filler (18), and in this case it is preferable to use electrocorundum granules with a fraction of 3÷20 microns.

The following describes an option for assembling one of the possible designs of a bimetallic gas-filled package used to implement the claimed invention. This method consists of sequential implementation of the following stages.

1) Rough abrasive cleaning of the mating surfaces of the workpieces of the main (1) and cladding (2) layers.

2) Drilling into the workpiece the main layer (1) of the channel (11), intended for connecting the interlayer space of the package and the ejector body (9).

Depending on the number of devices used, designed to release inert gas from the package during its heating and rolling, a corresponding number of channels (11) for gas exchange are made in the base layer blank during the assembly process of the package.

3) Welding to the workpiece the main (1) layer of the ejector body (9), containing a gas ejection unit, as well as a gas pressure equalization unit.

4) Finish abrasive cleaning of the mating surfaces of the workpieces of the main (1) and cladding (2) layers.

5) Degreasing the mating surfaces of the workpieces of the main (1) and cladding (2) layers.

6) Laying the cladding (2) layer on the workpiece of the main layer (1) with the formation of an interlayer gap by the mating surfaces.

7) Welding the contour of the package to form a sealed weld (3).

8) Replacement of the atmosphere in the interlayer space of the package with an inert gas (in particular, argon) by sequential evacuation and supply of inert gas through a through hole (not shown in the figures) in the ejector body (9).

At the moment the atmosphere is replaced, a hermetically removable plug (not shown in the figures) is installed in the channel (15), which is removed after equalizing the pressures in the interlayer space of the package filled with inert gas and atmospheric air.

9) Installation of a plug (not shown in the figures) into the through hole in the ejector body (9) and its subsequent welding.

10) Removing the removable plug from the channel (15) (not shown in the figures) and filling it with burnable sealant.

The assembled bimetallic gas-filled package is placed in a furnace, where it is heated to a temperature of 1000÷1290°C. After the package is released from the furnace, it is hot rolled on a thick-sheet reversing mill. It is preferable to ensure absolute compression in the first rolling pass of at least the thickness of the cladding layer (2).

The claimed method was tested on the equipment of the Stan-5000 metallurgical complex of JSC Vyksa Metallurgical Plant. Table 1 shows the parameters of the pilot production of clad steel sheets and the results of their tests. The obtained test results of the manufactured sheets, characterizing the strength of the connection of the layers and the continuity of their adhesion, indicate that when using the invention, the declared technical result is achieved.

The claimed method is intended for use in industry, namely for the production of clad steel sheets. Moreover, for the claimed method in the form as it is characterized in the independent claim of the invention, the possibility of its implementation has been confirmed using the means and methods described in the application or known before the priority date.

Claims (6)

1. A method for manufacturing a clad steel sheet, including heating a bimetallic gas-filled package containing a main and cladding layers of sheet material placed to form an interlayer space, and hot rolling of the package, in this case, a package is used with at least one device attached to it, including a gas pressure equalization unit and a gas ejection unit, or a package with at least one device attached to it containing a gas pressure equalization unit and at least one device , containing a gas ejection unit, Moreover, during the heating process of the package, a portion of the inert gas is released from the interlayer space of the package by means of a gas pressure equalization unit, which includes a channel communicating with the interlayer space of the package and containing a substance that prevents the free movement of the inert gas, and when performing the first pass of hot rolling of the package, it is ensured release of inert gas from the interlayer space of the package through a gas ejection unit, which contains at least one outlet channel communicating with the interlayer space of the package and covered with a steel plug, Moreover, they use a plug made of steel of the same class as the steel from which the main layer of the package is made, and the ratio of the working surface area of the steel plug S (mm ² ) to the smallest thickness h (mm) of its wall in the area of the working surface is S/h = 238÷982. 2. The method according to claim 1, in which electrocorundum granules with a fraction of 3÷120 microns are used as a substance that prevents the free movement of inert gas. 3. The method according to claim 1 or 2, in which said plug and the main layer of the package are made of pearlitic steel.

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