Braze Welding (1952)

braze welding is simply the joining together of two pieces of metal by melting bronze rod into the heated joint most of your repair jobs can be done by braze welding it's a fast easy way to do repairs or to make things out of metal in braze welding only the bronze rod is melted the molten bronze forms a puddle which is controlled by the flame as the puddle is moved along the joint more bronze is melted into it from the rod a flux is used to remove impurities when clean metal is kept at the proper temperature and flux is added the bronze melts and spreads evenly over the heated surface this is called tinning and tinning is the most important part of braze welding good tinning is a combination of correct heat and mechanical and chemical cleaning let's see how tenting works will do this by depositing bronze on a flat plate which first has been made mechanically clean by scrubbing with steel wool or a wire brush to make the metal chemically clean will use a braze welding flux on the rod first we heat the metal when it just begins to turn red we touch flux dipped rod to it see how the bronze melts and flows evenly over the heated area we move the puddle by moving the blowpipe heating the metal and melting the rod as we move along cleaning and fluxing are important to good tinning but so is proper temperature of the base metal here's what happens if the rod is applied before the plate is hot enough notice how the bronze melts off in drops and builds up instead of spreading out if the plate is too hot the bronze boils and runs to the edge of the heated area it behaves like water on a hot stove that white smoke is think being burned out spoiling the strength of the bronze now how about you're trying to braise well you can start by welding two steel plates together these are 1/8 inch thick both plates have been cleaned along the budding edges and for an inch or so on the top this cleaning is important any area to be braised welded must be free of dirt rust or oil before you start light your blowpipe and adjust the flame to neutral then add a little oxygen to produce a slightly oxidizing flame I'll watch over your shoulder while you work first make a tack weld at each end to hold the plates in position heat the metal to a dull red warm the end of the welding rod and dip it in flux touch the rod to the heated metal it will melt and flow evenly over the surface now go back to the right end play the flame in small circles over a spot the size of a quarter melt the surface of the tack weld and the rod and begin moving the puddle to the left the rear of the puddle will harden as you move along everyone finds in the beginning that the hot end of the rod will stick now and then if it is too close to the edge of the puddle don't try to yank it loose just turn the flame on it and melt it free when all the flux on the rod is gone dip the rod into the flux again fill in between the edges of the plates and build a bead about 1/8 of an inch above the surface spread a thin coating of bronze down in between the edges and back about 3/8 of an inch on each side point the flame along the line of weld in this position the plane pre heats the metal ahead of the puddle that's about all there is to it proper tinning is about 90% of making a good braze weld now you're ready to practice welding heavier metal notice that the edges of these pieces have been ground at an angle to form a V this V gives the bronze a larger surface to hold and the bronze can get right down to the bottom of the joint the weld area has been thoroughly cleaned including the top of the plates about an inch back from the V this time we'll use an ox well flux coated rod it's more convenient you don't have to dip this rod in the flux can for this job we'll need a larger tip on the blowpipe and we'll also use a welding rod one size larger braze welding is always done at the same temperature but thicker metal requires a greater volume of heat don't forget to add oxygen to the neutral flame the inner cone will be slightly shorter metals up to 1/8 of an inch can be welded in one pass heavier metals require two or more passes on this world you should use three passes start as before by making a tack weld at each end of the plates since heavier metals require more welding heat it's a good idea to preheat them slightly before welding play the blowpipe along the V from end to end in a long weld for a footer so keep the inner cone of the flame 1/2 to 3/4 of an inch above the top surface of the plate then heat the area at the starting point until it begins to turn red on this first pass let the bronze flow onto the surface and tin the V halfway up each side for a distance of about three inches when the metal starts to tin add welding rod into the puddle just as you did in the last weld move the blowpipe forward slowly keep the rod and blowpipe in motion the rod passing through the outer envelope of the flame the rod will melt too fast if it's in the center of the flame in thick metal the weld is made in layers one pass for each layer after tinning for about three inches go back and make a second pass over the first one here's what we mean by building up wells in passes or layers the first pass should fill the base of the V completely and carry about halfway up each side the shape of the top of the weld metal in this first pass should curve down toward the center on the second pass the V should be filled to the top of each side and have about the same shape on top as the first pass did the final pass extends above the surfaces of the plates and slightly beyond the V out unto the top surface now let's take a look through the site of the plate the first pass is laid down for a short distance and then the second pass is laid down on top of it for only a part of the distance the third pass is still shorter so that we have a step effect now we go back to the first pass and carry it along a few more inches the same with the second and third passes be sure to melt the first layer as you add more bronze so the two layers will be welded together 10 the upper half of the B as you move along also 10 the top surfaces a little beyond the bevel on both sides practice to get a smooth easy motion as you make the last pass keep the puddles smaller than before and build up the weld about 1/8 of an inch above the surface of the plate again be sure to melt the surface of the previous pass continue the weld in the same way first inning and then building up 2 or 3 inches at a time be sure to melt the bronze deposited in the previous pass it should mix well with the rod you add as you practice you'll find that controlling the puddle becomes easy the hottest part of the flame is right at the tip of the inner bright cone the size of the puddle can be controlled by moving that hotspot closer to or away from the puddle surface the same is true of the ride don't forget to build up the last pass for additional strength make it a little higher than the surface of the plate and a little wider than the top of the V you can control the puddle better by changing the direction of the blowpipe when you reach the edge of the plate point it towards the finished well this prevents the molten bronze from flowing out of the open end let's clean it off with a wire brush well that looks pretty good it was easy wasn't it braze welding is easy and fast too this shows what a good braze weld looks like if we cut right through it there is a good bond between the bronze and the steel all the way to the bottom that's enough for today's lesson let's review the important points you've learned rust oil and dirt must be removed from the area to be welded to permit proper tinning bevel the edges of the metal when it is more than one eighth of an inch thick if you don't have a flux covered rod use plenty of flux so that the metal being welded will be chemically cleaned tin the weld area carefully you can tell when you've got the proper heat the bronze flows smoothly and evenly keep the flame and rod in motion as you did today remelt deposited bronze when making additional classes in thicker metal learn to control the puddle spend some time practicing you've been working today on steel but you'll find the same principles apply to the braze welding of other metals cast iron copper and nickel alloys or when you join dissimilar metals all of these parts were repaired or fabricated by braze welding these cast-iron parts were easily repaired without disturbing the quality of the base metal this wheel had breaks in two spokes and two breaks in the rim now it's as good as new when you braze weld cast iron or copper use a welding tip two sizes larger than that specified in your welding tip metal thickness chart it will help keep the welding heat even be sure that you don't overheat cast iron just teeth the metal to a dull red glow this safety guard is one of the many things that can be made by braze welding four pieces of sheet steel were brace welded together and wire mesh tack welded to the edges of the frame this Christmas tree stand was made from a piece of pipe and steel plate a smaller size makes a good flux can holder this cylinder rack was made from used pipe and quarter-inch steel rod nine out of ten repairs in the shop for on the farm and many of the things you can make from metal can be braze welded it's the easiest way to join most metals just remember in all braze welding three important points have the metal clean use flux get good thinning