broken shaker grate - welding help

broken shaker grate - welding help

PostBy: gerard On: Wed Feb 11, 2009 1:19 pm

This morning I broke off the stub to my shaker grate. It's a two piece shaker grate combination and the grates are slaved together with a connecting bar so I can get by the rest of the season by shaking the other grate. I would like to repair it in the spring so I have a welding question. I have an ac stick welder and know that to do cast iron I have to pre heat it and cool it slowly for "cast to cast." I'd like to weld some mild steel square bar to replace the broken off portion since I don't have the broken piece to weld back. I was also thinking of welding some square tube over the whole thing and making another shaker handle out of mild steel since it won't be as brittle and prone to breaking as the cast. I'm looking for advice on what rod to use and technique to weld mild steel to cast. Thanx in advance for your input! :?:
gerard
 
Stove/Furnace Make: yukon dual fuel
Stove/Furnace Model: husky

Re: broken shaker grate - welding help

PostBy: Freddy On: Wed Feb 11, 2009 2:19 pm

(From
http://www.lincolnelectric.com/knowledge/articles/content/castironpreheat.aspGuidelines
This link is broken, either the page no longer exists or there is some other issue like a typo.
for Welding Cast Iron)


Background

Cast iron is difficult, but not impossible, to weld. In most cases, welding on cast iron involves repairs to castings, not joining casting to other members. The repairs may be made in the foundry where the castings are produced, or may be made to repair casting defects that are discovered after the part is machined. Mis-machined cast iron parts may require repair welding, such as when holes are drilled in the wrong location. Frequently, broken cast iron parts are repaired by welding. Broken cast iron parts are not unusual, given the brittle nature of most cast iron.

While there are a variety of types of cast iron, the most common is gray cast iron, and these guidelines are directed toward this type of material.

A few facts about cast iron help in understanding the welding challenges. Cast iron typically has a carbon content of 2% - 4%, roughly 10 times as much as most steels. The high carbon content causes the carbon to form flakes of graphite. This graphite gives gray cast iron its characteristic appearance when fractured.

When castings are made, molten iron is poured into a mold and allowed to slowly cool. When this high carbon material is allowed to cool slowly, crack free castings can be made. Remembering this is helpful when welding cast iron: during and after welding, the casting must either be allowed to cool slowly, or should be kept cool enough that the rate of cooling is not important.

A critical temperature in most cast iron is about 1450 degrees F. When at this temperature, conditions that can lead to cracking occur. While the arc will heat the casting to temperatures above this level, it is important that the casting not be held at this temperature for long periods of time.

Electrode selection

If the part is to be machined after welding, a nickel-type electrode will be required. Use Lincoln Softweld® 99Ni stick electrode for single pass, high dilution welds. Softweld 55 Ni is preferred for multiple pass welds. Sometimes, root passes are put in with Softweld 99 Ni, followed by fill passes with Softweld 55 Ni. For welds where machining is not required, and where the weld is expected to rust like the cast iron, Lincoln Ferroweld® stick electrode can be used.

To Heat, or not to Heat

In general, it is preferred to weld cast iron with preheat--and lots of it. But, another way to successfully weld cast iron is to keep it cool--not cold, but cool. Below, both methods will be described. However, once you select a method, stick with it. Keep it hot, or keep it cool, but don't change horses in the middle of the stream!

Welding Techniques with Preheat

Preheating the cast iron part before welding will slow the cooling rate of the weld, and the region surround the weld. It is always preferred to heat the entire casting, if possible. Typical preheat temperatures are 500-1200 degrees F. Don’t heat over 1400 degrees F since that will put the material into the critical temperature range. Preheat the part slowly and uniformly.

Weld using a low current, to minimize admixture, and residual stresses. In some cases, it may be necessary to restrict the welds to small, approximately 1-inch long segments to prevent the build up of residual stresses that can lead to cracking. Peening of weld beads can be helpful in this regard as well.

After welding, allow the part to slowly cool. Wrapping the casting in an insulating blanket, or burying it in dry sand, will help slow cooling rates, and reduce cracking tendencies.

Welding Techniques without Preheat

The size of the casting, or other circumstances, may require that the repair be made without preheat. When this is the case, the part needs to be kept cool, but not cold.

Raising the casting temperature to 100 degrees F is helpful. If the part is on an engine, it may be possible to run it for a few minutes to obtain this temperature. Never heat the casting so hot that you cannot place your bare hand on it.

Make short, approximately 1” long welds. Peening after welding is important with this technique. Allow the weld and the casting to cool. Do not accelerate the rate of cooling with water or compressed air. It may be possible to weld in another area of the casting while the previous weld cools. All craters should be filled. Whenever possible, the beads should be deposited in the same direction, and it is preferred that the ends of parallel beads not line up with each other.

Sealing Cracks

Because of the nature of cast iron, tiny cracks tend to appear next to the weld even when good procedures are followed. If the casting must be water tight, this can be a problem. However, leaking can usually be eliminated with some sort of sealing compound or they may rust shut very soon after being returned to service.

The Studding Method

One method used to repair major breaks in large castings is to drill and tap holes over the surfaces that have been beveled to receive the repair weld metal. Screw steel studs into the threaded holes, leaving 3/16” (5 mm) to ¼” (6 mm)of the stud above the surface. Using the methods discussed above, weld the studs in place and cover the entire surface of the break with weld deposit. Once a good weld deposit is made, the two sides of the crack can be welded together.
Freddy
 
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Re: broken shaker grate - welding help

PostBy: gerard On: Wed Feb 11, 2009 4:12 pm

outstanding info freddy - much appreciated. I'll give it a shot and see how I make out. Thanx for an informative post!
gerard
 
Stove/Furnace Make: yukon dual fuel
Stove/Furnace Model: husky

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Re: broken shaker grate - welding help

PostBy: djackman On: Wed Feb 11, 2009 6:46 pm

One of the biggest problems is variability in quality of cast iron, some welds almost good as steel and some just won't weld no matter what you do. While it's not supposed to work, I've had good luck with MIG on iron.

There's a ton of CI welding comments on the old engine messageboards since it's a common repair topic. http://www.smokstak.com is a good place to start.

A new handle from mild steel sounds like the real plan!
djackman
 
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Stove/Furnace Model: FT22 (aka 202) installed!

Re: broken shaker grate - welding help

PostBy: Putt On: Sat Feb 14, 2009 2:38 pm

Excellent information...
I always make short welds with Nickel rods.. Make a one inch (or shorter) weld, immediately peen the weld till it is cool
enough to leave your finger on it, repeat... When you start your weld, if you have no trouble starting your arc, you are
using too much current :-) use as little amperage as possible.. With a Nickel rod, you can weld steel to CI, but the same
rules apply, and you should direct most of the arc at the steel piece... If you wish, you can use a propane torch to pre-heat
the CI a bit, but don't over do it..

Putt...
Putt
 
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Re: broken shaker grate - welding help

PostBy: ciderman On: Sun Feb 15, 2009 9:43 am

Hello Gerard,
I too have a Yukon, and thanks to this forum, I found out that this is a known problem with thier grates. I broke the first one three years ago, and broke the second one two weeks ago. I called Yukon hoping they might help me out, but was told that since the grates lasted five years, I would have to pay full price plus shipping for new grates.

After that, I decided to try welding the old ones. I've welded numerous cast items in the past and always had good results with nickel rods and the procedures outlined by the other folks in this post, until now. The Yukon grates must be made of the lowest grade of cast possible. It was like trying to weld a sponge with a cutting torch.

It never hurts to try, but if your stove is only one or two years old, you might be better off getting on the phone with Yukon.
As for me, I'm going to finish out the season on wood, and if I still have a job this summer, I'm going to replace my Klondike with something else, it's a lousy coal burner and I've suffered enough! :D

Dave
ciderman
 
Stove/Furnace Make: DS Machine
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Re: broken shaker grate - welding help

PostBy: Poconoeagle On: Sun Feb 15, 2009 10:33 am

If there is enough room maybe just drill and pin or bolt a steel piece to the CI?? saves the welding frustration. also brazing is another method to attach. :?:
Poconoeagle
 
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Re: broken shaker grate - welding help

PostBy: gerard On: Tue Feb 17, 2009 10:15 pm

Well after thinking I could get by the rest of the season with the other grate, that one snapped off the other day so I'm an oil burner at the moment. this time though I was able to locate the nub since it had lodged in the shaker handle. The thing was hollow - bad cast. Must have trapped an air pocket during the pour so it was no wonder it broke off. I spoke to yukon today, told them about the problem and told them they should get a new set of grates from the foundry since the cast was bad. They asked me to send them the part so they could show the foundry and I was told that they would send me a new set of grates. Even so, I think I'm still going to try and affix some mild steel square tube and cob up a new handle. I'm thinking of trying JB Weld, kind of pouring it into the top of the square tube and letting it flow around the remaining, "nub". Says it's good to 600 deg so I may be ok as long as I bank the coal away from that end and let some ash build up. Going to be my sat project. I was also considering using some brazing rod I got that brazes aluminum and other metals. Might just be the ticket. I'll let everyone know if it works.
gerard
 
Stove/Furnace Make: yukon dual fuel
Stove/Furnace Model: husky

Re: broken shaker grate - welding help

PostBy: CapeCoaler On: Tue Feb 17, 2009 11:13 pm

Get the free cast replacements then use them to mold your own casting with good cast iron!
CapeCoaler
 
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