Welding cast iron stove top

[Rgillard]

Hi All,

A friend asked my brother to weld the top of a wood stove today. They heard it cracking in the middle of the night and it had a big split in it. We tried to weld it this evening but it started to crack even more. This is what we did. Btw we have no experience with welding cast, we just went on advise from a welder we know.

We cleaned the area thoroughly.
We grinded the crack into a V and cleaned either side of it
We heated the area for 10-15 mins with oxy propane.
As I welded my brother kept it hot in front of the bead.
After welding we kept heating but tried to let it cool slowly.
After about 15 mins of post heating we stopped
5 mins later we heard a crack and a new crack at 90 degrees to the original appeared and it also looks like the edge of the weld cracked.
When welding we noticed that the bead was not running like a normal 3.2mm rod. They were special cast welding rods that we got. It was welded using an arc inverter welder at about 180A

I have attached a few pics. If anyone can point us in the right direction as to what we did wrong I'd appreciate it.


Regards,
Ron

 

[Rgillard]

2 photos didnt load properly

 

[Rgillard]

other one

 

[bironacad]

Basically cast welding is challenging for guys like me with little experience because of it being so brittle. When you place localized heat from a welding rod to the cast the metal at that point expands faster then the surrounding area and the stress causes the cracking. I have successfully brazed a cook stove's lift out plate by heating the whole plate in a forge thereby relieving the localization of the heat and also making the metal more flexible with the general heating. I heard of a welder welding engine blocks by placing them in boiling water first using a forty five gallon barrel to boil the water then dipping the head in it to heat it to that temp making it slightly more pliable. Cooling should also be done in as uniform a fashion as possible because the shrinkage could also cause cracking. Steel will brake like crystal if cold enough and suddenly stressed and bend like taffy if hot enough. I am sure that the welders will now pipe in, lol.:laughing::thumbsup: Good luck.

 

[Shield Arc]

I'm so glad I saved this, saves a lot of typing:laughing:


Most of this was taken right out of Lincolon's book "Metals and How to Weld Them".

First off there are six different types of cast iron so you need to know the type of cast iron you are dealing with. Manifolds and cylinder heads are Gray cast iron. If preheating can be used, the preheat temperature for shielded arc welding (stick) should be held between 500-degrees and 1200-degrees. When oxyacetylene welding you should preheat between 900-degrees and 1200-degrees. You should never let the object being repaired get over 1450-degrees. Make your repairs, then place the object in your kitchen oven, (if it will fit) at 500-degrees for 24-hours. I would purchase the proper temp sticks from your local welding supply.

Nickel 99 can be cut, drilled, milled, and ground. Ni-55 can be ground. The low nickel rod can't be even ground.


Other suggestions:

Ni-44 for Tig rod

Certanium 889, (stick)

Crown Alloys 255 (stick)

Lincoln Softweld 55 (stick)

Harris / Welco 65 (stick)

Ni-55 (stick)

 

[yomax4]

Perfect application for Spray Powder Repair. Piece of cake..I've talked about this a bunch on here. The key is that you are not dumping a Bazillion Volts into the old brittle cast iron. You only get it maroon in color and start the spray. I enjoy fixing things like this.. If it were here I would heal it up tomorrow. :thumbsup:

 

[yomax4]

If you have to weld it..Some times when none of the Ni rods will work there is a secret weapon ( besides spray powder ) It's called Nickel Free Synthetic cast iron rod. Seems like one was MG 220. Harris has one too. When I used to run Ni Rods and make the job worse than it was, I would switch to Ni Free and often save the day.

 

[Tractor Seabee]

Hi All,

A friend asked my brother to weld the top of a wood stove today. They heard it cracking in the middle of the night and it had a big split in it. We tried to weld it this evening but it started to crack even more. This is what we did. Btw we have no experience with welding cast, we just went on advise from a welder we know.

We cleaned the area thoroughly.
We grinded the crack into a V and cleaned either side of it
We heated the area for 10-15 mins with oxy propane.
As I welded my brother kept it hot in front of the bead.
After welding we kept heating but tried to let it cool slowly.
After about 15 mins of post heating we stopped
5 mins later we heard a crack and a new crack at 90 degrees to the original appeared and it also looks like the edge of the weld cracked.
When welding we noticed that the bead was not running like a normal 3.2mm rod. They were special cast welding rods that we got. It was welded using an arc inverter welder at about 180A

I have attached a few pics. If anyone can point us in the right direction as to what we did wrong I'd appreciate it.


Regards,
Ron

In my past we repaired a lot of cast iron equipment with arc rods made by Castolin at Castolin Eutectic Group . They make a lot of unique repair and fabrication products both arc and brazing. We used a copper alloy arc brazing rod for a lot of repairs and joining disimilar metals such as stainless steel to copper. Any welding supply house has or can get their products. They come with instructions. Castolin has a complete engineer and R & D unit and can answer any question. We did not have to preheat castiron much. I think your stove to is probably a low grade gray or white cast iron. As mentioned by others the exact alloy has to be known to select the right CI arc rod. We also did torch brazing with great results with minor pre-heating. Some low grade CIs are a real problem to repair though as they are made from mixed scrap and the alloy could be a wide range of metals. The arc brazing rod can be used for a lot of applications and is good stuff to have arouind the repair shop.

Ron V

 

[yomax4]

In my past we repaired a lot of cast iron equipment with arc rods made by Castolin at Castolin Eutectic Group . They make a lot of unique repair and fabrication products both arc and brazing. We used a copper alloy arc brazing rod for a lot of repairs and joining disimilar metals such as stainless steel to copper. Any welding supply house has or can get their products. They come with instructions. Castolin has a complete engineer and R & D unit and can answer any question. We did not have to preheat castiron much. I think your stove to is probably a low grade gray or white cast iron. As mentioned by others the exact alloy has to be known to select the right CI arc rod. We also did torch brazing with great results with minor pre-heating. Some low grade CIs are a real problem to repair though as they are made from mixed scrap and the alloy could be a wide range of metals. The arc brazing rod can be used for a lot of applications and is good stuff to have arouind the repair shop.

Ron V

The Arc Brazing Rod is an interesting product with a lot of different uses. I had some of a different brand once and it was called the same but it was a Silicon Bronze Stick rod. Flowed out very nice at low amps. We welded a broken cast iron barbell with it and it worked very nice. Worth looking into. It actually flows into the depths of the cracks too.

 

[Tractor Seabee]

In my past we repaired a lot of cast iron equipment with arc rods made by Castolin at Castolin Eutectic Group . They make a lot of unique repair and fabrication products both arc and brazing. We used a copper alloy arc brazing rod for a lot of repairs and joining disimilar metals such as stainless steel to copper. Any welding supply house has or can get their products. They come with instructions. Castolin has a complete engineer and R & D unit and can answer any question. We did not have to preheat castiron much. I think your stove to is probably a low grade gray or white cast iron. As mentioned by others the exact alloy has to be known to select the right CI arc rod. We also did torch brazing with great results with minor pre-heating. Some low grade CIs are a real problem to repair though as they are made from mixed scrap and the alloy could be a wide range of metals. The arc brazing rod can be used for a lot of applications and is good stuff to have arouind the repair shop.

Ron V

Forgot one important point in the above post: When repairing cracks the first thing to do is drill a 1/4" hole all the way through where the crack ends and/or the beginning if not at an edge. That will keep the crack from growing as you add stress from the welding heat