Welding at the Forge
by John R. Smith
[Reprinted from the Manual of blacksmithing, circa 1902. The publication has been reprinted by Lindsay Publications Inc., Bradley, Illinois and is available from several suppliers.]
Weldability is one of the most valuable properties possessed by wrought iron and mild steel. Welding is often the alternative of drawing down or of upsetting; correct heat and cleanliness are the chief requisites. Welding heat corresponds with the temperature at which the metal is in a state of partial fusion on the surface. At that temperature it is extremely plastic. and a little hammering will cause two surfaces to adhere and possess as much strength as the other parts of the metal. The welding heats for iron and steel differ, and even also the heat for different qualities of iron and different qualities of steel. Any iron will require a much greater heat than steel, and the better the quality of iron, the higher the welding heat that it will stand without becoming burned. At a welding heat iron gives off dazzling sparks; steel shows only an intense yellow, and gives off few sparks. The ascertaining of the correct heat is a matter for experience entirely, and no description or illustration can take the place of practical lessons.
To illustrate the process of welding more clearly, two plain examples: one a collared rod, and the other a plain straight rod. are given.
Fig. 80--Bar with Shoulder End.
Fig. 81.--Forming Ring on Anvil Beak.
Figure 82.--Ring Slipped over Mandril.
Taking the shouldered end (Fig. 80), first cut off the rod, A, and then prepare to fit over it the ring, B, for which take a square bar, say 1/8 inch larger than the finished section required, and, with a hot set, cut off one end diagonally or else fuller it down. Then bend the bar roughly into circular form over the anvil horn (Fig. 81). and cut off to the required length, with a sloping face to lap upon and match the first diagonal. The metal must have sufficient lap to allow for welding, and for dressing off and finishing. If the ring is fairly true, it will be ready to go into the fire for welding; but if not, slip it over a mandrel, Fig. 82, and give the scarfed joint a neat appearance, either with the hammer alone or with one of the hollow tools previously described. Then slip off the ring and flatten the faces (Fig. 83). This is precisely the plan that would be adopted in welding a separate ring.
Fig. 83. -- Smoothing Faces of Ring with Flatter.
To weld it to the rod, the ring is slipped over the end of the rod, care being taken to remove any scale adherent to either, and they are then put into the clear fire. Sand may be sprinkled over the work. But with a clear fire it is not necessary, and is frequently not done. When the welding heat is attained, which for wrought iron is of a dazzling whiteness, when the iron seems ready to melt, and particles appear ready to drop off, and a rapid evolution of sparks takes place, the work is removed from the fire placed on a V-block and the scarf joint and the ring are hammered all round with a hand hammer, the rod with its ring being continually turned into fresh positions on the V-block. If a hammerman's services are available, the hollow tool is used. and a few blows upon it consolidate and smooth the surfaces. Then the faces and shoulders are finished by means of a heading tool, having tool of a size suitable to take the rod, a few blows with hammer and flatter finishing off both the under shouldered face and the upper flat face. Then It may be necessary to work over the circular part again with the hollow tool. This is to finish the surface. for the welding heat is soon past, and if the union of the joint faces is not fully effected in the first few seconds. It will be more or less imperfect.
To weld a rod, a scarfed joint is employed, and plenty of metal is wanted to allow for hammering the joint together and for finishing it afterwards without reducing below correct sizes; therefore, the ends of the bar have not only to be scarfed, but to be slightly upset. The meeting ends, which have been cut off square, are laid horizontally upon the anvil, and are upset or beaten over, while nearly at a welding heat. Then they are laid over the edge of the anvil, and scarfed or beaten down diagonally with a fullering tool, the face of the scarf being made rounding rather than hollow. Both ends having been served precisely alike, they are put back into the fire, and raised to the welding heat. Lift the work vertically out from the fire; do not drag it through the coal. Any particles of dirt that are present will show as dark specks on the white-hot iron, and should be brushed off with a switch of brushwood.
Fig. 84.--Ends Scarfed and Upset ready for Welding.
The Smith and his helper lay the scarfed ends together, as shown in Fig. 84, and then two or three blows with the hand hammer cause the ends to unite, and the rod can then be rapidly turned about on the anvil while the joint is consolidated all round with hand hammers or sledges. The top and bottom swages can be used for imparting the finish required. It will be apparent that without the first enlargement or upsetting of the rods, the process of welding and swaging would have thinned the rod at the welded section below that of the other portions. How much to upset and how much to scarf are matters for experience.
This article was published in Blacksmith's Gazette, February 1997 issue. It has been edited to fit the format of our Blacksmith's Gazette Internet Site.
This page was last updated on February 24, 1997.