CORUS
Look for a reputable repair facility that does metal stitching. I have had quite a few repairs done to both cast iron and cast steel with very good results.
Agree with Poppeye for cast iron, but not for steel--IF it's an easily welded composition. What steel do you have.
Reynolds-French did some excellent CI stitching for my company about 20 years ago on a 7,000+ HP diesel that put 2 rods (and pistons) right thru the side of the block.
The steel is 50 years old and has a yield value of over 300 MPa.
I know nothing about stitching although it sounds like inserting a bolt across the crack. The crack is through the thickness so stitching across the crack and down the length of the structure probably isn't possible as it's a few yards high. Secondly any additional material might intefere with other components. Can the stitch be made flush with the surface and made to act like a staple, perhaps pre-tensioned? Is welding possible even though the crack may be 100 mm deep?
Metal stitching is used to make a crack leak-tight, but does not restore any strength. A hole is drilled parallel with and centered on the crack, then a special metal rod material is inserted. The next hole is drilled right next to the 1st, but it overlaps the rod a bit. The process is repeated to the end of the crack. A steel "armature" is used to restore the strength/rigidity to the casting. In our case, the result was stronger than the orig. design and hasn't leaked any oil or water since (~20 years).
If there is no room for an internal or external armature, I don't think you can use the technique, unless you don't need the strength.
Thanks for the information Metalguy.
As a last question it has been claimed that porosity within the casting has stopped crack growth. I presume that this could be imagined as the metal looking like a sponge in the region of the crack tip. Would this in fact stop the crack from growing further as they claim? I could imagine the weaker material reducing the stresses within that region but could also imagine that any imperfections would enhance crack growth, perhaps eminating from a position further from the crack.
Most of the steel castings can be weld repaired unlike cast irons. Also they do not need such high levels of skills or technology. Common practices are sufficient to repair weld yje casting. Select the proper gradeof welding rods which any manufacturer can provide and get started without worrying too much. If need be provide a stress relief treatment after the weld repair. Conduct all NDT test for weld assurance and start working.
A single pore can stop a crack because it acts like a drilled hole and reduces the stress at the crack tip. Unfortunately it only helps right at the pore, and your crack sounds pretty big (long crack-tip). Therefore I don't think the porosity is capable of stopping it.
