SupportingColumns Ironcorrosionand • repair Brian Morton tries to dispel some of the myths about welding of cast and wrought iron. In my paper presented to the IHBC in Shrewsbury at the beginning of April, I attempted to dispel the generally held views that it is not possible to repair wrought iron using welding techniques and further, the views that cast-iron cannot be welded. I was concerned to hear one of the Conservation Officers, attending the IHBC Annual School asking the blacksmith at the working farm as to whether castiron could be welded and was told by him that it could not. I thus, thought it would be helpful to give some references that will confirm the views given in my paper. The major reference is a book produced by the Steel Construction Institute entitled The appraisal of existing iron and steel structures produced in 1997 where current thinking with regard to continued use of iron and early steel structures is appraised very well. This suggests that both the welding of wrought iron and cast-iron is difficult, but does not rule it out. A further useful document was reprinted from Metal Construction 1998 Vol. 20 No.2 (February) obtainable from the Welding Institute, Abington Hall, Abington, Cambridge CBl 6AL. With cast-iron there are other jointing techniques using the stitch weld system patented by Metalock Ltd,Dartford, Kent, involving the drilling of holes either side of cracks or breaks in castiron, the joining of the two materials with a malleable metal then the insertion of threaded bar into pre-tapped holes along the line of the joint making the whole joint tight. The photograph shows this method. The difficulties of repairing wrought and cast-iron should not be underestimated and it is absolutely essential that an experienced specialist (usually a specialist blacksmith) should analyse, and more particularly should carry out tests with the particular materials to be joined before the repair technique is agreed. I have found by experience that although the materials to be joined Context 58 June1998 Exampleof stitch welding of iron. can be analysed to establish their makeup (principally carbon content), the man with the practical experience generally provides the answer. It is necessary to establish the reasons for the cracking or failure that has occurred and it is suggested that if there are high loads stressing the particular member then it may well be that mechanical fixings may be more appropriate. I would not, for example, repair a cast-iron beam that had failed in tension due to high loading by welding, the mechanical fixing system would certainly be appropriate. The particular skill in joining these metals relates to the blacksmith's knowledge of the various welding techniques. When metals can be taken off site, wrought iron can be fire welded, i.e. lengths of wrought iron can be made red hot and beaten together. Cast-iron needs to be heated and welded and allowed to cool slowly or, alternatively, the Metalock system can be used. On site repairs, generally of small sections of wrought iron, can be carried out by butt welding using bonds or by brazing techniques (brass) or, ideally, the use of Manual Metal Arc (MMA)welding using strips of wrought 31
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