Welding engine block

You will need to devise some sort of fixture to keep the pieces in alignment prior to welding. Having done that, there are two basic approaches to prep the areas to be joined. The most basic is to grind the area. If you choose to do that, grind a "U" and not a "V" groove to a depth that allows for proper penetration. It sounds as if this application allows for welding on both sides of the parts to be joined. That is ideal. When both sides cannot be welded, the groove must be deep enough to penetrate just short of burn-thru.

The second approach to prep is the best in my opinion. This involves the use of an airless gouging electrode such as my #1250 of 1/8" diameter at 150 amps AC. This provides for several advantages which are explained in detail on the web site. One of the many advantages that you will notice is the virtual elimination of pinholes in the weld. With either method, you should grind the top surfaces clean to promote good adhesion in the transition zone.

The welding electrode that will give the best resistance to cracking and the highest tensile strength on cast iron is the #521 which is a special electric brazing rod with a hardness of 200 BHN (approximately 15 RC) which promotes ductility due to the relative softness. Don't be confused by the text that states "#521 is good for wear resistance". Wear resistance comes from a low coefficient of friction and self lubricity as applied in applications such as bushing repair or fabrication. The tensile strength is 90,000 PSI. More details of this alloy are on the site as well. The diameter of choice is 3/32" which is the most commonly used in cast iron applications regardless of electrode choice. Use DC+ polarity and be prepared to move fast as this alloy burns off much faster than nickel electrodes of the same diameter. Lay stringer beads. Do not weave.

A slight preheat in the area of 200°F to 300°F will be beneficial and heat should be concentrated on the mass and allowed to migrate to the smaller pieces. Preheat will already be established if the gouging rod is utilized. To further relieve any residual stresses, peen the area vigorously as it cools.

In regard to 7018, some success can be had when welding ductile or nodular cast irons as the outside shell of those materials closely resembles mild steel in chemistry and grain structure. It is not something I would choose to do, espcially if the repair may need to be repeated again at some point in the future. Steve

• U.S. Alloys/Weld Tech

When grindig out for the weld prep should a die grinder (rotory file) be used vs a stone wheel. I was always concerned about contamination of the weld surface by the wheel grit and bonding agents and its reaction to the deposited weld... perosity etc.

Why is 3/32" rod the most common for cast iron welding. Assume its requires less heat to deposit and that the smaller beads help keep the weld area temperature more uniform.

Why is the stringer bead better than a weave for the cast iron welding or is this recommended due to the US Alloy recommendtion.

Regarding grinding with a steel bit as opposed to an abrasive disk: You are correct to assume that the disk will introduce contaminants into the weld. Not only are the components that make up the disk a possible contaminant, but anything the disk was previously in contact with can also pose as a possible source for contamination. I would go one step farther and submit to you that the bit and the disk share one shortcoming. Both grinding methods will leave the surface area "slick" and smooth. They will also tend to "smear" existing contaminants from the various layers of metal in the process of removing metal. Some of the reasons I prefer the #1250 is that it will blow metal away as you progress and will seal the root of the weld which is a potential source of hydrogen and other contaminants. The #1250 also establishes a preheat which removes moisture, another source of hydrogen. (Hydrogen can produce pinholes and cause embrittlement.) When used correctly, the #1250 will also create an anchor profile and increase surface area. It can often eliminate the need to tack weld as the parts will be fused at the base line in addition to being cleaned, sealed, and preheated. The #1250 can be used to preheat an entire area by utilizing an extended arc.

Your next question concerned the selection of the diameter of the electrode: You are correct that a 3/32" electrode will deposit metal with less heat input to the base material. The bigger picture has to due with reducing stresses from shrinkage of the bead. This is directly proportionate with the diameter of the electrode.

This ties in directly with the third question of stringer bead vs. weaving technique. Again, this is to reduce residual stresses in the weldment. There are many considerations to be contemplated when choosing a proper procedure for repairing cast iron. One consideration is the type or grade of cast iron to be repaired. Others include the service environment, thickness, accessablility, shape, color match requirements, etc.

Depending on these considerations, electrodes composed of various combinations of alloys of Nickel, Chromium, Iron, Copper, Cast Iron, and Soft Steel or unalloyed versions of many of these metals are chosen. The process equipment and decisions as to preheat or not to preheat are also based on these factors. The same can be said for the choice of welding technique to be used.

For example, I spoke to a gentleman yesterday via phone who needed a procedure and filler metals for repairing a butchering kettle. The alloys he purchased from me and the procedure I recommended for him were quite different than what I have recommended for your project. There is not enough room here to describe all of the scenarios that are playing out inside my head as I type this reply to your posting.
Steve

We are going to add welding reference materials to our site soon and I have been reviewing materials from several publishers. I thought of you as I reviewed the one we spoke of by phone. It will be included in our selection. I'll have to recommend it to the more informed and technically oriented folks like yourself. We will also have something for those who may not be interested in something quite so "detailed" shall we say. By the way, nice posting under "Welding High Carbon Steels".
Merry Xmas to you and yours Greg ,
Steve

I would weld the the block back up if it was mine. Just look at the numerous posts on welding cast iron on what to do. I would use a angle, channel or plate to hold all the pieces for alignment while welding. 7018 does not work on cast iron! 1/8" rod is a good size for any type of welding and depending on how what temperature of preheat, about 120amps depending also on rod brand, but thats a starting point.

T_Bone

I believe that the tractor was used for manure loading and it was driven of a concrete floor/wall and the front end wheels went over and the tractor fell on its belly and cracked the block ear..... . at least this appears what happened.The tractor was worked with the ear cracked so I assume balance is ok.

I have done some welding mostly mild steel and can weld quite well but cast iron has given me problems is the past. I welded a F-12 cracked head hole just below the rocker arm shaft with success but had to grind out a number of times due to perosity in the weld and cracking along the weld bead.

I will try Ni-rod 1/8" @120 amps with localized preheat with oct/acet torch. I will use DC portable gas engine Hobart welder in lieu of my 220V miller AC/DC since the Hobart welds considerably better smoother arc etc. I also have 308 ss and monel rod.... will they be any better than Ni-rod. Suppose best is to try on an junk car engine block first to get all just right. Well I have nothing to lose and makes sense to attempt.