weld cracking problem on grey cast iron grid work

Date 02-23-2008 22:44

I have welded Baldwin frames using Ni99. It was welded at room temperature, and no warpage was detected. The Beckstein frames and the Steinway frames reportedly are not "Good Gray Castings". Thus I had a fusion problem. Some passes would stick and others would not stick. I took them to a cast iron welding specialist who had more equipment. (Open side ovens which placed the frame directly in the flame. The sides were then built up on the base with firebrick to close the oven, a segmented lid was assembled over it. The lid would be opened and the excavation was welded up right in the flame.) I watched each of these frames be torch welded using a Cast Iron Rod and Eutectic Type 14 Flux. This was done in the preheating oven and allowed to cool overnight. MT was performed and no cracks were found. Yamaha castings are reportedly "Mehanite" castings and can presumably be welded electrically.

By aevald

Date 02-24-2008 08:55

Hello daniel blide, you can definitely weld some cast irons without necessarily using preheating methods and ovens, you can also use them as Joe included very nicely in his post. I have had similar problems to those that you talked of in your post, the difference that I would include in your method, is peening of the weld deposits. Cast iron is a very rigid material and doesn't deal well with weld or heat induced stresses. Preheating allows the temperature differential to be minimized and to help with keeping internal stresses to a minimum, long slow cooling after preheating also promotes stress minimization. The peening that I referred to helps to minimize the build up of stresses. By making relatively small, short, weld beads and then peening them(I use a smooth rounded-tip tack hammer, 1/32" radius approximately)the weld bead will be stretched out while it is still somewhat soft and hot and help to control internal stress, when completed the peened surface resembles the surface of a golf ball with the divots basically touching the edges of one another, you don't want to be too radical, just lightly tap, tap, tap. Do as you first described, running these short little beads and not proceeding onto the next one until you can touch the piece comfortably with your hand. Also try to step around on the piece and if welding on both sides of it anywhere, work from one side and then to the other. Hope this makes some sense, good luck and best regards, aevald

By Stephan (***)

Date 02-24-2008 16:26

Hello Allan,

I guess this is the most complete advice in "cold" grey cast iron welding I have ever read.

As well as Joe Kane's application was very interesting to read.

Excellent!

I guess beside executing short stringer beads (20... 30 mm) the slight intermediate peening is a very effective tool to minimize the risk of cracking.

I have welded the grey cast iron machine bed of a large compressor approx. 18 years back and have used Iron-Nickel stick electrodes (diameter was 2.5 mm [~ 1/10 inch]). Short beads and slight peening to inverse the tensile- partially into compressive stresses were - at least in my interpretation - the basis for success.

As I have recently been told by an old colleague, the compressor does even work properly to this day :-).

Best regards,
Stephan

By aevald

Date 02-24-2008 20:01

Hello Stephan, it is good to see that you have a little time to "play" on the forum here lately. Still enjoy your posts immensely. As far as cast iron goes, generally it can present some of the most challenging repair possibilities IMHO. Most of the cast that I have repaired over the years I have done with either GTAW, SMAW, or brazing, haven't had much access to the filler rod and fluxes, so I have had very little exposure to oxy-fuel welding of it. Have also done most of my repair attempts and successes with the "Cold" methods, as I don't have ready access to the proper ovens for the other methods.
With GTAW welding as the process, I have used eutectic cast iron welding filler rod, or have knocked the flux off of Nickel 55 or similar SMAW electrodes, or in limited cases have used silicon bronze filler rod. With the SMAW process have used the Nickel 55 mostly, a bit of Airco 375 I believe it is called, besides those I have used some of the specialty cast welding rods that are available through many of the specialty rod providers, but haven't really been as impressed as the price tags would possibly indicate. Then of course when possible have simply brazed items together using the high temperature fluxes that are recommended for cast iron brazing. With all of these choices and the possibilities of more, I usually find success some of the time, but have had to use a number of different approaches other times to end up with acceptable results. Good to see you on here again, hope to see and hear from you much more in the future. Best regards, Allan

By Stephan (***)

Date 02-25-2008 07:23

Hello Allan,

thanks a lot for your interesting additional technical comments and of course... your very friendly words, which do honoring and gladden me outstandingly!

I have never used the GTAW process for repairing grey cast iron but I can imagine very well that it might be a good method to accomplish those "cold" repairs, in particular by beneficially using its good controllability in terms of thermal energy input and filler metal addition.

It is always a true privilege for me to be allowed to learning something new, as this is always the case with your explanations.

Once again thanks and my best regards,
Stephan

By aevald

Date 02-25-2008 09:09

Hi Stephan, the thing I like about using the GTAW process for working on cast iron, besides controllability with regards to heat, has to do with also being able to work the porosity out of the weld pool. Many times if you are stick welding you will see pores in the deposit, you have to go back and grind and try again, with the GTAW method you can sometimes very carefully use the amperage variability of the foot-pedal or other amperage control apparatus and some tungsten manipulation to "work" the porosity out. Many others can do more justice to the scientific explanations for how things work or why they work, I have been fortunate to have been shown many methods in welding by others that accomplish specific tasks that hold up to whatever testing will verify sound results. These days I have come to see the reasoning for why a lot of these methods have worked, or not worked, yourself and many others who frequent this site have been responsible for that. This has also allowed me, in many cases, to site these reasons when students have asked for explanations for why things are the way they are. Once again, for that I thank you and the many others who so readily share this information with the rest of us. Warm regards, Allan

By Stephan (***)

Date 02-25-2008 14:30

Hello Allan,

thanks for adding these descriptions.

Good point!

As you have mentioned "...grind and try again...", I felt remembered on "sulfur" which is a "first order crack causer" not only, but in particular in all high grade Nickel containing weld deposits.

So the use of sulfur free grinding disks when processing grey cast iron repairs (e.g. for removing the cast's oxide layer prior to welding) should be a must, as well as the general avoidance of every other sulfur contamination of the area to be welded.

Best regards,
Stephan

By daniel blide Date 02-25-2008 23:50

I just wanted to thank everybody for the information it is great to hear all the different techniques everyone has. I think I am going to try using the cold method possibly with gtaw process using a stick electrode with the flux removed. I am also going to peen the weld immediately after depositing the the weld, I hope this works. If any body has any suggestions on filler wire I am all ears. I was trying to figure out which rod would offer the most elasticity to help prevent the cracking.
Thanks,
Dan

By aevald

Date 02-26-2008 00:21

Hello Dan, whichever electrode you decide to try, attempt to completely remove all of the flux from the outside of the rod. I generally use a hammer and lightly tap on the flux to crack and break it from the core wire and once I have removed the majority of it that way I use 50 or 60 grit sandpaper or a scotchbrite pad to remove the rest of it and shine it up real good so that it is clean and free of any residual dust.
Most of the time I have used NI 55 smaw rod, although just about any cast iron rod will probably do. As far as looking for an electrode that has the greatest amount of elasticity you might consider looking to some of the filler rod designation and descriptions and take note of the elongation percentages, likely the rods with the higher elongation numbers will also have the greatest elasticity.
In certain cases, I have had the best success with this method when using a drag angle on the torch as opposed to a push angle. You will likely have to do a bit of experimentation to achieve the best success. Please be sure to post your progress and let us know how it goes. Good luck and regards, Allan

By Superflux (****)

Date 02-26-2008 03:30

daniel blide,
I,ve had good results on engine blocks using 308 and 309 GTAW filler rods. The key to success seems to be "clean and peen" , and keep it cool. Since others have noted possible problems associated with sulfur, looking back on it, I always used rotary files (carbide burrs) for the final dress or prep. I used a "Foredom or Dremel" brand flex shaft tool with 1/4" collet. Some times on complex shapes, such as spoked gears, heat must be applied to other areas for proper expansion and contraction to eliminate cracks appearing on opposing sides. An auto darkening hood for rapid application of peening before the weld regains color. Cast iron is always a challenge, and by the way, never guarantee crack repairs on exhaust manifolds. They seem to have about 70/30 (or is it 30/70) success rate.

By aevald

Date 02-26-2008 03:49

Hello Superflux, great additional tips and suggestions. Best regards, aevald

By aevald

Date 02-26-2008 02:33

Hello again Stephan, I can understand not wanting to have sulfur present in the area of welding and also making sure to grind off the"skin" or surface of the casting. Now for my question. I was not aware of sulfur being a part of some grinding discs and wondering if you can elaborate further on this topic. I am curious as to how one can determine, if in fact, a particular type of disc would have sulfur in it. I am also aware that certain discs are designed for grinding on steel, stainless steel, aluminum, masonry, and other specific applications. Which type of wheel lacks the sulfur and thus is recommended for working with cast iron or nickel based alloys, the stainless steel type? Would greatly appreciate enlightenment on this. Best regards, Allan

By DaveBoyer (*****)

Date 02-26-2008 05:30

Allan: It is My understanding that SOME SMAW alloy rods use a mild steel wire and put the alloying elements in the flux. How can You be sure to have a rod where the alloy is in the wire and not in the flux when using a SMAW rod with the flux removed? Is there anything in the electrode designation, or do You need to look in the manufacturer's literature? Or is this FC2002 and You take Your chances.

By aevald

Date 02-26-2008 05:45

Hello Dave, point taken and to be honest I haven't researched that aspect of it that closely. I have basically only used NI 55 and Airco 375 cast rods in this manner. As to how other rods play out with respect to your question I really don't have an answer other than to agree that it would be worth looking to the manufacturers rod description to verify one way or the other. Thank you for bringing that up for consideration. Best regards, Allan

By Stephan (***)

Date 02-26-2008 08:10

Hi Allan,

once again a hearty thanks for replying!

Well, honestly I am no expert in grinding but the first time I have experienced that this detail might be considered as being a concern was when I have SMA welded parts of an annealing furnace using 36Ni/16Cr (~ E330) stick electrodes.

I was instructed at that time to use sulfur free grinding wheels for avoiding any undesired sulfur input. That was new for me as well, that time. As I was interested in this detail I have tried to find out (the Internet wasn't born yet) if there is any criterion for the recognition of these wheels. The only item was and is still today that the sulfur free discs had the admission of the German KWU (Kraftwerk Union) which was a SIEMENS subsidiary leading in the construction of many nuclear power plants. This special "KWU" admission stood and stands for highest product quality of each tool being used in mechanical engineering, just as a "knightly accolade".

I suppose that this statement doesn't really answer your kind question. Thus I have tried to find out (thanks God the Internet is already born meanwhile :-)) to find any hints on this particular topic.

Please let me attach what I have found:

http://www.enotes.com/how-products-encyclopedia/grinding-wheel

http://www.abrasiveproducts.net/Kasco/msds.htm

http://www.qqma.com/en/cpdetail.asp?id=7768

Hmm, finally I personally would say that even by "normally" not knowing what kinds of constituents were used for producing a grinding wheel, one should "normally" presume that sulfur containing ingredients can be present.

In really critical applications I would thus "trust" the data sheets of the grinding wheel supplier, which is in Germany a bit easier as I suppose. Since in Germany we can explicitly have a search for even the "KWU admission" guaranteeing that no (or lowest) sulfur, iron and chloride contents could be measured.

Hope that I could shed some light on it.

My best regards,
Stephan

Attachment: walter-abrasives_ALCAM.pdf (821k)

By labib

Date 02-27-2008 18:58

where the size and location of the equipment to be welded makes preheating impossible, but the design is such that expansion and contraction caused during welding will warp or highly stress the metal, the following steps should be observed :
(1) Pause between passes to allow heat to dissipate.
(2) Lightly peen with round hammer before each deposits solidifies and while it is still hot.
(3) By making separate weld deposits and then going back over and filling in, you will avoid localized excess heat.
Do not weld on a surface that has been prepared by grinding wheel. Most grinding wheels are contaminated with foreign matter. The grinding wheel can rub this contamination into the surface of the iron. More important the grinding wheel picks up graphite with each revolution.
The incomparable electrode MAGNA 777 welds all types of cast iron and steel to cast iron, without preheating, fully machinable,non cracking,higher tensile strength than most types of cast iron.