GB2120136A

GB2120136A - Method of forming a cladding unit for a building

Info

Publication number: GB2120136A
Application number: GB08306515A
Authority: GB
Inventors: Nigel Anthony Walker; Bernard Johnson; Malcolm Harry Bradley
Original assignee: ALFAB Ltd
Current assignee: ALFAB Ltd
Priority date: 1982-03-10
Filing date: 1983-03-09
Publication date: 1983-11-30
Also published as: GB8306515D0; GB2120136B

Abstract

A corner unit for steel cladding for a building, for use where the corrugations in the cladding will extend horizontally on the building, is formed from a sheet of the cladding by cutting a series of apertures (1, 3) across the corrugations to permit the sheet to be bent to the desired angle, welding adjacent edges of the apertures together, coating the welded corner unit with a heat curable plastics coating material, and heating the corner unit to cure the coating. To ensure that the corner unit does not corrode more readily as a result of the bending and welding operation, a layer of corrosion resistant metal, preferably zinc or cadmium, is plated on to the welded corner unit before the plastics coating material is applied. The plating is preferably electrolytic. <IMAGE>

Description

SPECIFICATION Method of forming a cladding corner unit for a building This invention relates to a method of forming a cladding corner unit for use in the construction of a building.

In the construction of industrial buildings, such as factories, warehouses, and offices, it is common to provide a steel framework which supports upper floors and the roof, and to fill in the spaces between frame members with steel cladding sheets which, being non load bearing, can be made light in weight and decorative in appearance.

For rigidity, the sheets may be corrugated, ridged or ribbed, the corrugations, ridges or ribs typically extending vertically in the completed building. For convenience, the term "corrugations" is used hereinafter to include ribs, ridges, channel formations, and the like.

Design considerations have created the need to form corners in the cladding with the corrugations extending perpendicularly to the corner, i.e. running horizontally when used at a junction between two vertical walls. The cladding sheets may be formed into a corner unit by cutting out apertures, bending to close the apertures, and then welding the sides of the closed apertures together. The cladding sheets are preferably formed of mild steel, galvanised to resist corrosion, and the welding and subsequent grinding to remove excess metal at the weld leaves bare metal which if not treated can corrode. Typically the cladding sheets are coated with heat-cured plastics material, such as polyvinylidene fluoride (PVF2) paints, which have high durability and resistance to corrosion.

Because of the relatively high curing temperature of these materials, approximately 240 C, conventional anti-corrosion paints cannot be used to treat the bare metal surfaces after welding. It has been found that the heat treatment removes the anti-corrosion paint. Further, it is necessary to pre-treat any surface being coated with PVF2 with an alkaline phosphate pre-treatment material. This again cannot be carried out satisfactorily where anti-corrosion paints have been applied.

Because of the relatively thin gauge of the steel used (0.6 to 0.75mm) regalvanising of the steel cannot be carried out, the metal distorting at the high temperatures involved.

Accordingly, therefore, the present invention provides a method of forming a corner unit from a sheet of steel cladding having corrugations therein, the corner unit being such that the corrugations extend perpendicularly to the corner, comprising cutting a series of apertures across the corrugations to permit the sheet to be bent to the desired angle, welding adjacent edges of the apertures together, coating the welded corner unit with a heat curable plastics coating material, and heating the corner unit to cure the coating, wherein a layer of corrosion resistant metal, preferably zinc or cadmium, is plated onto the welded corner unit before the plastics coating material is applied.

Preferably the metal is plated on electrolytically, to a depth of 10 microns, for example.

It has been found that corner units manufactured in accordance with the method of the invention can equal the basic hot dipped galvanised steel sheets in corrosion resistance, when plastics coated.

Reference is made to the accompanying drawings, in which: Figure 1 is a perspective view of a portion of cladding sheet before formation into a corner unit; and Figure 2 is a corner unit formed in accordance with the invention.

The cladding sheet is formed from a mild steel sheet pressed to form rectangular corrugations extending parallel along the sheet. To form a right-angled corner unit, as shown in Fig. 2, portions of the unbent sheets are cut out to enable bending. The portions cut out consist of an isosceles right-angled triangle 1 in each side portion 2 of the corrugations and a rectangle 3 in the inner base 4 of the corrugations, connecting the bases of the triangles 1. The cut out portions are illustrated in Fig. 1 as shaded.

The sheet is then bent along a line joining the apexes of the triangles, the fold line being illustrated in Fig. 1 by a chain dotted line 5.

The sides of the triangles are bought together, together with the sides of the rectangles 3 in the bases 4 of the corrugations. These adjacent sides are then welded together and the excess metal ground off, followed by polishing to leave a continuous smooth surface. The completed corner unit, as illustrated in Fig. 2, is then plated electrolytically with a layer of zinc or cadmium, the zinc or cadmium adhering both to the bare steel and to the zinc already applied by galvanising. After alkaline phosphate pre-treatment, or a passivating dip in chromic acid solution, a primer coat is applied over the whole surface of the corner unit and heat cured and then a coat of approximately 25 microns thickness of PVF2 is applied by spraying. The coat is hardened by heat curing at a temperature of approximately 235 to 240 C for ten to fifteen minutes. The primer used on the inner surface of the corner unit may be a polyvinyl butyl resin primer.

The corner unit may then be installed on the building in exactly the same manner as the unbent sheets, and is found to have equal weather resistance to the unbent sheets, which are plastics coated during manufacture.

1. A method of forming a corner unit from a sheet of steel cladding having corrugations

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Method of forming a cladding corner unit for a building This invention relates to a method of forming a cladding corner unit for use in the construction of a building. In the construction of industrial buildings, such as factories, warehouses, and offices, it is common to provide a steel framework which supports upper floors and the roof, and to fill in the spaces between frame members with steel cladding sheets which, being non load bearing, can be made light in weight and decorative in appearance. For rigidity, the sheets may be corrugated, ridged or ribbed, the corrugations, ridges or ribs typically extending vertically in the completed building. For convenience, the term "corrugations" is used hereinafter to include ribs, ridges, channel formations, and the like. Design considerations have created the need to form corners in the cladding with the corrugations extending perpendicularly to the corner, i.e. running horizontally when used at a junction between two vertical walls. The cladding sheets may be formed into a corner unit by cutting out apertures, bending to close the apertures, and then welding the sides of the closed apertures together. The cladding sheets are preferably formed of mild steel, galvanised to resist corrosion, and the welding and subsequent grinding to remove excess metal at the weld leaves bare metal which if not treated can corrode. Typically the cladding sheets are coated with heat-cured plastics material, such as polyvinylidene fluoride (PVF2) paints, which have high durability and resistance to corrosion. Because of the relatively high curing temperature of these materials, approximately 240 C, conventional anti-corrosion paints cannot be used to treat the bare metal surfaces after welding. It has been found that the heat treatment removes the anti-corrosion paint. Further, it is necessary to pre-treat any surface being coated with PVF2 with an alkaline phosphate pre-treatment material. This again cannot be carried out satisfactorily where anti-corrosion paints have been applied. Because of the relatively thin gauge of the steel used (0.6 to 0.75mm) regalvanising of the steel cannot be carried out, the metal distorting at the high temperatures involved. Accordingly, therefore, the present invention provides a method of forming a corner unit from a sheet of steel cladding having corrugations therein, the corner unit being such that the corrugations extend perpendicularly to the corner, comprising cutting a series of apertures across the corrugations to permit the sheet to be bent to the desired angle, welding adjacent edges of the apertures together, coating the welded corner unit with a heat curable plastics coating material, and heating the corner unit to cure the coating, wherein a layer of corrosion resistant metal, preferably zinc or cadmium, is plated onto the welded corner unit before the plastics coating material is applied. Preferably the metal is plated on electrolytically, to a depth of 10 microns, for example. It has been found that corner units manufactured in accordance with the method of the invention can equal the basic hot dipped galvanised steel sheets in corrosion resistance, when plastics coated. Reference is made to the accompanying drawings, in which: Figure 1 is a perspective view of a portion of cladding sheet before formation into a corner unit; and Figure 2 is a corner unit formed in accordance with the invention. The cladding sheet is formed from a mild steel sheet pressed to form rectangular corrugations extending parallel along the sheet. To form a right-angled corner unit, as shown in Fig. 2, portions of the unbent sheets are cut out to enable bending. The portions cut out consist of an isosceles right-angled triangle 1 in each side portion 2 of the corrugations and a rectangle 3 in the inner base 4 of the corrugations, connecting the bases of the triangles 1. The cut out portions are illustrated in Fig. 1 as shaded. The sheet is then bent along a line joining the apexes of the triangles, the fold line being illustrated in Fig. 1 by a chain dotted line 5. The sides of the triangles are bought together, together with the sides of the rectangles 3 in the bases 4 of the corrugations. These adjacent sides are then welded together and the excess metal ground off, followed by polishing to leave a continuous smooth surface. The completed corner unit, as illustrated in Fig. 2, is then plated electrolytically with a layer of zinc or cadmium, the zinc or cadmium adhering both to the bare steel and to the zinc already applied by galvanising. After alkaline phosphate pre-treatment, or a passivating dip in chromic acid solution, a primer coat is applied over the whole surface of the corner unit and heat cured and then a coat of approximately 25 microns thickness of PVF2 is applied by spraying.The coat is hardened by heat curing at a temperature of approximately 235 to 240 C for ten to fifteen minutes. The primer used on the inner surface of the corner unit may be a polyvinyl butyl resin primer. The corner unit may then be installed on the building in exactly the same manner as the unbent sheets, and is found to have equal weather resistance to the unbent sheets, which are plastics coated during manufacture. CLAIMS

1. A method of forming a corner unit from a sheet of steel cladding having corrugations therein, the corner unit being such that the corrugations extend perpendicularly to the corner, comprising cutting a series of apertures across the corrugations to permit the sheet to be bent to the desired angle, welding adjacent edges of the apertures together, coating the welded corner unit with a heat curable plastics coating material, and heating the corner unit to cure the coating, wherein a layer of corrosion resistant metal is plated on to the welded corner unit before the plastics coating material is applied.

2. A method according to Claim 1, wherein the corrosion resisant metal is zinc or cadmium.

3. A method according to Claim 2, wherein the corrosion resistant metal is cadmium.

4. A method according to any preceding claim, wherein the layer of corrosion resistant metal is 10 microns thick.

5. A method according to any preceding claim, wherein the layer of corrosion resistant metal is applied electrolytically.

6. A method according to any preceding claim, wherein the plastics coating material is poly(vinylidene fluoride).

7. A method of forming a corner unit, substantially as described with reference to the drawings.