WO2014048629A1

WO2014048629A1 - Roller table and method of rolling a material

Info

Publication number: WO2014048629A1
Application number: PCT/EP2013/066645
Authority: WO
Inventors: Mark BRUNGER
Original assignee: Siemens Plc
Priority date: 2012-09-28
Filing date: 2013-08-08
Publication date: 2014-04-03
Also published as: GB2506395A; GB201217336D0

Abstract

A roller table for a metal hot rolling mill has a heat shield comprising heat-insulating panels (22, 24, 26, 32) mounted relative to a material travel path (28) extending along the table over at least a part of the length of the table. The insulating panels further comprise heating elements and the roller table further comprises a controller for controlling operation of the heating elements.

Description

ROLLER TABLE AND METHOD OF ROLLING A MATERIAL

This invention relates to a roller table, in particular for a metal hot rolling mill and a method of rolling a material on the roller table.

Rolling hot material on a roller table, for example metal slabs or bars, such as steel bars results in a temperature drop for the slab and particularly for thick slabs, the edges suffer greater heat loss than the middle. Roller table heat shields are known, for example as described in EP0857523, which are designed to reduce the rate of loss of heat. Although these heat shields prevent a certain amount of heat loss during rolling, there are still some situations in which a reheating process is required in order to achieve the required final dimensions and properties. In order to avoid having to provide this reheating facility, the mill operator may restrict the size of product being rolled. Even so, some products may have poor quality edges and the overall yield is reduced by the need to remove these edges at the end of the rolling process.

In accordance with a first aspect of the present invention, a roller table for a metal hot rolling mill comprises a heat shield comprising a one or more heat-insulating panels mounted relative to a material travel path extending along the table over at least a part of the length of the table; wherein the or each insulating panel further comprises heating elements; and wherein the roller table further comprises a controller for controlling operation of the heating elements.

Preferably, the heating elements comprise electrical resistance elements.

Preferably, the heat insulating panels comprise at least one of upper heat insulating panels above the material transport path, or lower heat insulating panels beneath the material transport path.

Preferably, the lower panels are arranged in groups between successive rollers of the roller table.

Preferably, the table further comprises side heat insulating panels.

In accordance with a second aspect of the present invention, a method of rolling a material on a roller table having a heat shield comprising heat-insulating panels mounted relative to a material travel path, wherein one or more of the panels comprise heating elements; the method comprising determining a required temperature profile for the material to be rolled and controlling operation of the heating elements in each panel according to the required profile. Preferably, the method further comprises measuring the temperature of the material as it enters the roller table and comparing the temperature with the required temperature profile and operating the heating elements according to the result of the comparison.

Preferably, the required temperature profile is set to exhibit a reduction in temperature along the length of the material to be rolled.

Preferably, the method further comprises controlling operation of heating elements in at least one of side panels, upper panels or lower panels, respectively beside, above or below the material travel path.

Preferably, the heating applied to the panels is varied across the width of the panels.

This allows the heat that is re-radiated across the width of the product to be controlled.

Preferably, the heating applied to the panels is varied along the length of the roller table.

Preferably, the heating is applied to the panels before a head end of a product to be rolled arrives at the heat insulating panels.

Controlling the heating in this way enables the appropriate amount of heat to be applied at the head end of the product, even after a gap between products being rolled.

An example of a heat insulating panel according to the present invention will now be described with reference to the accompanying drawings in which:

Figure 1 shows a transverse cross section of a typical transfer roller table incorporating heat insulating panels;

Figures 2a to 2c illustrate heat insulating panels according to the present invention, for use in the example of Fig.1.

There are limitations with existing roller table heat shields. The most effective current heat shields are panels which have a membrane which is heated by radiation from the hot material. The membrane is backed by insulating material to prevent heat loss from the back of the membrane. Once the membrane reaches a sufficiently high temperature it re-radiates almost as much heat as it absorbs and thus significantly reduces the heat loss from the material. When there is no material present the membrane cools down. This is particularly a problem on mills with a long gap time between successive slabs or bars. Consequently when the head end of the next slab or bar arrives, the membrane is not effective for the first part of that slab or bar. It only becomes effective once it has heated up again.

The present invention addresses this problem by the use of the electrical heating to raise the temperature of the membrane in advance of the head end of the material arriving. A detailed example of this is described below with respect to Figs.1 and 2. The roller table of Fig.1 is mounted over a flume F and comprises a series of parallel rollers 2 mounted in bearings 4, 6 on a lower support structure 8 of the table and driven by motors 10. An upper structure or lid 12 extends the length of the table in a number of discrete sections each of which comprises a cantilever frame 14 mounted on fixed, coaxial pivots 16 that run parallel to the table. The cantilever frames 14 can be swung upwards from the bottom position shown by means of hydraulic rams 18 connected between each frame 14 and a fixed mounting 20. Top insulating panels 22 and side insulating panels 24 are carried on the frames 14, and fixed side insulating panels 26, define, with the rollers 2, a space which provides a travel path 28 for hot material to be carried along the roller table by the rollers.

Lower heat-insulating panels 32 between the rollers enclose the hot material path from below. All the panels 22, 24, 26, 32 are preferably of a re-radiating type and have hot faces which when directed towards the material on the roller table, limit the loss of heat by radiation from the material. There is an option, when using pivotable panels as described for example in EP0677337 and EP0744229, for the panels to be able to be titled away as indicated in Fig.1 by panels 32'. However, the invention is applicable to both fixed and pivotable panels.

The upper panels 22 and the side panels 24 are arranged in laterally extending groups each fixed to a respective cantilever frame 14. These panels 22, 24 are essentially fixed in place on their pivotable cantilever frames 14, although they may have some small freedom of movement on their attachments to the arms to

accommodate thermal effects. Bumper bars 34 projecting below the upper panels are associated with a sensing mechanism (not shown) for distorted hot material, in order to be able to trigger upward pivoting of the frames 14, so that the panels carried by the frames can be swung clear of the roller table to be protected from damage. In order to overcome the problems of conventional rolling arrangements, the present invention incorporates a heat source into one or more of the heat insulating panels having a passive heat radiating membrane. Thus, the problems of heat loss from the product during rolling of the hot metal in the rolling mill and heat loss from the heat shields in intervals between individual products are addressed by respective passive and active means, increasing the likelihood that the required final dimensions and properties can be obtained without having to go through a reheating process. Instead of restricting the size of product being processed to ensure the products can be rolled to the required specification, or passing the products through one or more reheating phases, with the risk of poor quality edges and reduction in yield, the invention enables the product to be kept at suitable temperature during rolling.

As shown in Fig. 2c, the heat source is preferably in the form of heating elements 40 mounted within a thin layer 45 of insulating material immediately behind the passive heat radiating membrane 44 of the panel construction. The heating elements may be mounted in channels formed within the surface of the insulating layer 45. A more substantial layer of insulation 43 is provided behind the heating element layer 45 to prevent heat loss in that direction. The heat in the product in the rolling process is used to take the membrane to a temperature that will enable it to re-radiate the heat back to the product or parts of the product where the temperature is lower. Incorporation of heating elements into the panels enables the membranes to greatly reduce the amount of heat that they take out of the first part, head end, of product that enters the system. It also enables the heat that is re-radiated to be varied across the width, or the length of the product, or both, to achieve specific product requirements, in particular to control the heat re-radiated to the head end of the product. By heating the panels in advance of the product arriving at the panels in the heat shield of the roller table, the effect on the head end of loss of heat from the radiating panels during gaps between rolled products is reduced or prevented entirely.

Figs. 2a and 2b show the panels 22, 24, 26, 32 with heating elements 40 and electrical supply 41. In the example illustrated in Figs.2a and 2b, the heating elements are electrical resistance elements and are electrically controlled so that the amount of heat that they put into the membrane may be varied according to process requirements. Other types of suitable heating elements include electrical radiant heaters, electrical induction heaters, or gas burners with radiant heating elements. Typically, the heating elements are incorporated in one or more of the top panels 22 and optionally in the side and bottom panels 24, 26, 32, but the specific panels which include heating elements is not restricted to this. There may be sections of the roller table heat shield which do not lose the heat so quickly between passes, so conventional re-radiating panels are sufficient. Even if all of the panels incorporate heating elements 40, the controller may switch only some of the heating elements on, according to the process requirements.

For example, if heat loss from the edges is a particular issue, then only the upper and lower panels 22, 32 which cover the edges of the material being passed through are used. Alternatively, the heaters are switched on to heat the first part of the product as it passes along the roller table, but switched off as an front section has passed and no further heat is added to the middle parts of the product. The heaters may be switched on again for a rear section of the product. A combination of heating of only front and rear section across the width, but the middle section on at the edges may be carried out instead. The controller 42 may be programmed as required for each pass.

The heat-insulating panels may be of a type which is fixed in place during use, or may be pivotable between operative and inoperative positions or able to move to clean off build up of scale, such as are described in EP0677337 and EP0744229.

The advantage of incorporating the heating elements into each heat insulating panel is that heat can be applied accurately to specific parts of the material being rolled by controlling each heating element individually. This is more efficient than using induction edge heaters, as the design of the heat-insulating panels allows the heat to be directed where it is required, rather than radiating in all directions and yet only reaching a limited area of the material.

Claims

1. A roller table for a metal hot rolling mill, the table having a heat shield comprising heat-insulating panels mounted relative to a material travel path extending along the table over at least a part of the length of the table; wherein the insulating panels further comprise heating elements; and wherein the roller table further comprises a controller for controlling operation of the heating elements.

2. A table according to claim 1, wherein the heating elements comprise electrical resistance elements.

3. A table according to claiml or claim 2, wherein the heat insulating panels comprise at least one of upper heat insulating panels above the material transport path, or lower heat insulating panels beneath the material transport path.

4. A table according to claim 3, wherein the lower panels are arranged in groups between successive rollers of the roller table.

5. A table according to claim 3 or claim 4, wherein the table further comprises side heat insulating panels.

6. A method of rolling a material on a roller table having a heat shield comprising heat-insulating panels mounted relative to a material travel path, wherein the panels comprise heating elements; the method comprising determining a required temperature profile for the material to be rolled and controlling operation of the heating elements in each panel according to the required profile.

7. A method according to claim 6, further comprising measuring the temperature of the material as it enters the roller table and comparing the temperature with the required temperature profile and operating the heating elements according to the result of the comparison.

8. A method according to claim 6 or claim 7, wherein the required temperature profile is set to exhibit a reduction in temperature along the length of the material to be rolled.

9. A method according to any of claims 6 to 8, further comprising controlling operation of heating elements in at least one of side panels, upper panels or lower panels, respectively beside, above or below the material travel path.

10. A method according to any of claims 6 to 9, wherein the heating applied to the panels is varied across the width of the panels.

11. A method according to any of claims 6 to 10, wherein the heating applied to the panels is varied along the length of the roller table.

12. A method according to any of claims 6 to 11, wherein heating is applied to the panels before a head end of a product to be rolled arrives at the heat insulating panels.