problems with hk40 castings

[barnyj74]

I am a welder in a stainless foundry, every time they cast hk40, the casting is lpi tested. the casting is always covered in red spots, that are not cracks. we gouge all the spots, and weld them with er-310 and no matter what we do, the spots don't go away. also, when we burn into the casting with the tig welder, the metal looks real porous under the surface. any advise on this would be much appreciated. thank you

 

[arunmrao]

If the casting is a Nitrogen containing one, you need to look at this process and the final Nitrogen content in the casting. Else, HK 40 casting is not prone to porosity due to gas. I presume that the mold is sufficiently cured( in case of resin mold) so that no gas is evolved.

Hope it helps.

 

[Guest102023]

Is this effect found only near the casting surface ot throughout?

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[sdjvar]

Hi Barnyj74, Can you explain what's the process of your casting? Is it investment cast, sand cast or shell cast? The main idea is to fix the problem in the foundry melting department. I don't think it's a good idea to weld or deburr all the red spots and weld repir. It's a reaction that's happened during and after metal solidification. Give more input so may be I can sugeest couple ways to solve this problem. Sonny

 

[barnyj74]

im not real familiar with the melting and pouring process, I do know that they use a quick set sand mold,gas holes are one problem we run into, one thing I have discovered, is that if I weld the red spots with 330 then beat the weld with a jack hammer, the spots go away. but I know this is only covering up the spot. it would be nice to fix the problem the right way, instead of just covering them up.the guys running the melting department swears that shaking out the casting as soon as possible and letting it cool fast, is the best way. as I said, im just a welder, but it seems to me, that maybe the casting is cooling to fast and the impurities are getting trapped inside, instead of floating to the surface. they use two small ladels to pour from both ends, and most of the bad areas seem to be in the center of the casting, like it is all being pushed to the center. they have added more and bigger risers, but that has made no difference at all

 

[pandithan]

weld with 309

 

[arunmrao]

For HK 40 castings 330 electrodes are suitable as no weld cracks are noticed. Can you describe the castings being processed? Early shakeout etc, are not helpful. Ask them if they have tried using Foseco sleeves, that have a necked down core, a filter and castings can be directly poured through them. The yield improves and inclusions are under control.

Hope it helps..

 

[jwhit]

Unfortunately, things like gas holes, sand and slag inclusion and shrinkage are inherent problems in castings. As I read over the posts I get a little concerned about the preparation for welding that goes into these castings. Most of the specifications require grinding or burning out of the defective area to clean metal or at least to an acceptable indication level. I hope that I misinterpreted the part about burning into the surface with the tig torch, that isn't your means of excavating the casting is it? All that accomplishes is to spread the trapped inclusions or gas around the puddle, it doesn't remove them completely. Regardless, grinding after arc burning is necessary to insure a clean excavation. Also, peening over a weld to seal off defects is strictly forbidden by the standards I'm familiar with. ER310 or 310HC is the recommended filler for this alloy. If you go to the SFSA (Steel Founders Society) webpage, you will find a series of free downloads, several of which you may find interesting. Look for SFSA High Alloy Welding S7, this will give you welding information and recommended procedures for welding these materials.
Often foundries find fixing problems like this to be easier after the casting is made (by weld repair), rather than during the actual making of the casting.

 

[barnyj74]

jwhit, we normaly air arc and grind the bad spots out, when I talked about burning into the casting, I noticed that at the end of the spot I was welding, I was seeing real porous looking metal just under the surface, but yes, the company is just making us cheat and do whatever it takes to get these parts out. I know that er310 is the recommended filler, but it just hasent been working out.they had us try nickle82 but it only helped on the cracks not the crappy spots. I can gouge out a bad spot with a hog grinder, lpi the spot to make sure the bad spot is gone, weld it, grind it down, do another lpi on the area, and the red spots re-appear. its almost like its pulling crap out of the surrounding metal. these parts are used in petro chemical furnaces so I don know if 308 or 309 would be ok for this application. thanks for all the input, I now have some direction to start looking in. I just want to fix these casting right, and only do it once. thank you again