GB2064079A

GB2064079A - Surface coated copper furnace components

Info

Publication number: GB2064079A
Application number: GB7941327A
Authority: GB
Original assignee: British Steel Corp
Current assignee: British Steel Corp
Priority date: 1979-11-30
Filing date: 1979-11-30
Publication date: 1981-06-10

Abstract

This invention relates to water- cooled copper furnace components, e.g., tuyeres and coolers, in which the leading end of the component is fusion-coated with a protective copper-chromium alloy. The alloy may also include zirconium, and the coating may be effected by welding or plasma-spraying.

Description

SPECIFICATION Surface coated copper furnace components This invention relates to water-cooled copper components for furnaces, e.g. coolers and tuyeres for blast furnaces.

Such components are made from high conductivity copper and may be cast and/or forged. High conductivity copper is utilised because of the primary necessity for minimal resistance to heat transfer but there are drawbacks in so far as the refractoriness of copper is low, i.e. it can be burnt away in the furnace environment, and it does not offer much resistance to abrasion and oxidation in this environment.

Hitherto, various attempts have been made to combat this problem; for example, refractory materials have been bonded to the nose portion of tuyeres but the disadvantage here is that the coating is fragile, and the expansion coefficients of the parent copper and the refractory coating/bond interface are different; with the thermal cycling to which the component is subjected this differential expansion resuits in spalling and ultimately the thermal conductivity of the coating diminishes to practically zero. Efforts to increase the abrasion/oxidation resistance likewise have disadvantages, for example aluminium has been spray coated on to the nose of the component and then heat treated to produce layer of say 0.5 mm thick aluminium bronze. Whereas this provides satisfactory protection against abrasion/oxidation the conductivity is significantly reduced with detrimental affect.

Other methods adopted utilise the casting-in of such refractory or abrasion resistant materials. In all cases however there is a loss in high conductivity in the very area which one is trying to protect.

It is an object of the present invention to mitigate this problem.

From one aspect the invention provides a water-cooled copper component for insertion in a furnace wall, in which the leading end of the component projected towards the furnace interior is fusion coated with a protective chromium copper alloy.

The components may be coolers and tuyeres and the alloy may also include zirconium; the fusion coating may be effected by welding or plasma spraying.

The component may be heat treated before going into service to promote hardening but since the component is to be used at elevated temperatures this may be dispensed with and reliance be placed on this function being performed automatically in service.

In accordance with this invention then, this additional step performed on a standard production item results in a marked improvement in the lifetime available in service. As distinct from 'inserts' in the casting there is no alteration made in the standard casting procedure adopted, the thickness and area of the coating laid down may be varied at will and the material selected has the properties of high hardness and abrasion resistance, it retains its physical properties at the elevated temperature to which it is subjected and it possesses and retains high conductivity.

Various instances of the invention are described below, by way of example, with reference to the accompanying drawing in which Figure 1 illustrates a diagrammatic view of a blast furnace cooler and Figure 2 illustrates a diagrammatic view of a tuyere.

Referring now to Figure 1 the cooler has a body portion 1 cast in high conductivity copper, hollowed to provide channels for cooling water conducted through inlet and outlet ports 2, 3. The leading end or 'nose' of the cooler which is subjected to the harsh furnace environment has overlaid on it a surface 4 comprising an alloy of chromium and copper, e.g. copper embodying between 0.5% and 1.2% chromium. The alloy may be deposited by a metal insert gas welding process to a thickness of 3 mm or more.

Alternatively the alloy may additionally include, at: the expense of copper, zirconium up to a maximum of 0.5%.

The thick deposited layer of the alloy fused on to the comparatively large mass of the high conductivity copper body cools very quickly; this retains the chromium (and zirconium where added) in solution, effectively eliminating the need for solution heat treatment to obtain an artificially rich solid solution.

Figure 2 shows a tuyere the water-cooled body 5 of which has likewise been overlaid with the Cr/Cu alloy, the coating 6 extending around the inside and outside of the nose portion.

In both cases precipitation (age hardening) is promoted in service bearing in mind the temperatures to which they are subjected, but optionally a separate step of heat treatment may be performed for this purpose.

Although the coating described has been effected by m.i.g. welding other methods could alternatively be employed e.g. arc welding or plasma spraying. Further, the coating technique described could be employed on other furnace components, e.g. copper lance heads.

1. A water-cooled copper component for insertion in a furnace wall, in which the leading end of the component projected towards the furnace interior is fusion coated with a protective chromium copper alloy.

2. A component according to Claim 1, wherein the alloy also includes zirconium.

3. A component according to Claim 2, wherein the alloy comprises copper embodying zirconium up to a maximum of 0.5% and between 0.5% and 1.2% chromium.

4. A component according to Claim 1, wherein the alloy comprises copper embodying between 0.5% and 1.2% chromium.

5. A component according to any one of Claims 1 to 4, wherein the fusion coating is effected by

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Surface coated copper furnace components This invention relates to water-cooled copper components for furnaces, e.g. coolers and tuyeres for blast furnaces. Such components are made from high conductivity copper and may be cast and/or forged. High conductivity copper is utilised because of the primary necessity for minimal resistance to heat transfer but there are drawbacks in so far as the refractoriness of copper is low, i.e. it can be burnt away in the furnace environment, and it does not offer much resistance to abrasion and oxidation in this environment. Hitherto, various attempts have been made to combat this problem; for example, refractory materials have been bonded to the nose portion of tuyeres but the disadvantage here is that the coating is fragile, and the expansion coefficients of the parent copper and the refractory coating/bond interface are different; with the thermal cycling to which the component is subjected this differential expansion resuits in spalling and ultimately the thermal conductivity of the coating diminishes to practically zero. Efforts to increase the abrasion/oxidation resistance likewise have disadvantages, for example aluminium has been spray coated on to the nose of the component and then heat treated to produce layer of say 0.5 mm thick aluminium bronze. Whereas this provides satisfactory protection against abrasion/oxidation the conductivity is significantly reduced with detrimental affect. Other methods adopted utilise the casting-in of such refractory or abrasion resistant materials. In all cases however there is a loss in high conductivity in the very area which one is trying to protect. It is an object of the present invention to mitigate this problem. From one aspect the invention provides a water-cooled copper component for insertion in a furnace wall, in which the leading end of the component projected towards the furnace interior is fusion coated with a protective chromium copper alloy. The components may be coolers and tuyeres and the alloy may also include zirconium; the fusion coating may be effected by welding or plasma spraying. The component may be heat treated before going into service to promote hardening but since the component is to be used at elevated temperatures this may be dispensed with and reliance be placed on this function being performed automatically in service. In accordance with this invention then, this additional step performed on a standard production item results in a marked improvement in the lifetime available in service. As distinct from 'inserts' in the casting there is no alteration made in the standard casting procedure adopted, the thickness and area of the coating laid down may be varied at will and the material selected has the properties of high hardness and abrasion resistance, it retains its physical properties at the elevated temperature to which it is subjected and it possesses and retains high conductivity. Various instances of the invention are described below, by way of example, with reference to the accompanying drawing in which Figure 1 illustrates a diagrammatic view of a blast furnace cooler and Figure 2 illustrates a diagrammatic view of a tuyere. Referring now to Figure 1 the cooler has a body portion 1 cast in high conductivity copper, hollowed to provide channels for cooling water conducted through inlet and outlet ports 2, 3. The leading end or 'nose' of the cooler which is subjected to the harsh furnace environment has overlaid on it a surface 4 comprising an alloy of chromium and copper, e.g. copper embodying between 0.5% and 1.2% chromium. The alloy may be deposited by a metal insert gas welding process to a thickness of 3 mm or more. Alternatively the alloy may additionally include, at: the expense of copper, zirconium up to a maximum of 0.5%. The thick deposited layer of the alloy fused on to the comparatively large mass of the high conductivity copper body cools very quickly; this retains the chromium (and zirconium where added) in solution, effectively eliminating the need for solution heat treatment to obtain an artificially rich solid solution. Figure 2 shows a tuyere the water-cooled body 5 of which has likewise been overlaid with the Cr/Cu alloy, the coating 6 extending around the inside and outside of the nose portion. In both cases precipitation (age hardening) is promoted in service bearing in mind the temperatures to which they are subjected, but optionally a separate step of heat treatment may be performed for this purpose. Although the coating described has been effected by m.i.g. welding other methods could alternatively be employed e.g. arc welding or plasma spraying. Further, the coating technique described could be employed on other furnace components, e.g. copper lance heads. CLAIMS

2. A component according to Claim 1, wherein the alloy also includes zirconium.

5. A component according to any one of Claims 1 to 4, wherein the fusion coating is effected by welding or by plasma spraying.

6. A component according to any one of Claims 1 to 5, wherein the coating is hardened by heat treatment conducted prior to the component entering service.

7. A component according to any one of Claims 1 to 6, which comprises a tuyere or a cooler.

8. A water-cooled copper component substantially as herein described.