Posted by Stuart on February 14, 2010 at 16:16:36 from (64.198.86.189):
In Reply to: Re Welding Heads posted by LarryM on February 14, 2010 at 13:32:20:
You can use either fusion or powder welding to repair a crack depending on the application. Either way, the first step is to fully identify the cracks, then grind them out with a hand-grinder.
If a crack is being repaired by fusion welding, first preheat the head to 1300 degrees F (cherry red) in an oven. . .Preheating is absolutely essential to minimize thermal shock, and to relax the metal so it won't distort when the torch is applied to the casting.
When the head preheat temperature has stabilized (it takes about an hour), a "neutral flame" oxyacetylene torch with slightly more oxygen than acetylene is used to melt the cast iron (which melts at approximately 2700 degrees F). You can use several varieties of cast iron filler rod and borax flux. The trick here is to keep the weld clean by adding a little flux so the impurities will rise to the top. The impurities can then be floated out of the repair area with the torch.
If your building up a valve seat, make a carbon graphite plug to fill the hole, then weld up around it. The puddle will be about half-an-inch deep and maybe two-inches in diameter. It takes a lot of heat to do this, about 5000 degrees F.
After the crack has been filled, a long, slow cool-down follows. This step is also important to prevent the head from recracking. If cast iron cools too quickly, one of two things can happen. The surrounding metal can shrink away from the weld causing new cracks to open, and/or the carbon in the iron can turn into carbide making the metal too hard and brittle to machine. Therefore, the casting must be cooled very slowly to prevent these undesirable metallurgical changes.
Wrap the head in an insulating blanket and keeps the head in a hot box so the head will cool at a rate of no more than 200 degrees F per hour.
At these rates, it can take quite awhile for the head to cool down to ambient temperature: 8 hours to overnight. So one can't be in a hurry when fusion welding cast iron heads. Once the head has cooled, it is cleaned to remove the scale, then rough machined and submersion pressure tested in hot water at 100 psi for leaks
We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]
Today's Featured Article - Box Plow Blues - by Tom Schwarz. One of the first implements most tractor owners obtain is the box plow. For very little money, this piece of equipment promises to plow and flatten any hill or vale on your ranch road or farm. At least that's what I thought! As simple as a box plow appears, it can be rather challenging to make work correctly. In our sandy soils of Florida, traction is king. You can never have wide enough tires or heavy enough weights to get all the traction you want … unless you own a monster tractor. U
... [Read Article]
Latest Ad:
Oliver 550 Diesel runs like a watch three point hitch pto engine gone threw about two hundred hours ago nice clean tractor
[More Ads]
All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy
TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.
