Chromalloy

[stringer bead]

Ok I just got moved to our facility that is welding Chromealloy anyone ever weld on it or know anything about it causeI have no idea what this stuff is all about any input would be helpful.

[MXtras]

Sounds like chromolly? It's alloy steel - like 4130 or 4140 used for structural purposes - like race car chassis and motorcycle chassis.

It must be preheated prior to welding and the cooling must be controlled and done slowly to prevent cracking later in it's life. Post welding stress relieving is a good idea but most folks don't do anything after welding other than cool the structure slowly. Thats about all I can recall - I don't mess with it very often. I would hit Google now that you know what the material is - if this is the material you are talking about that is.....

Scott

[stringer bead]

Yeah I heard that it has to be preheated to 500 degrees and about the contolled cooling. I heard it is really susceptable to gas trap and can crack weeks afterr the welding proccess is complete.

[MXtras]

Here - read this:

http://www.aws.org/wj/apr03/AWfeature.html

Scott

[EvanK]

Ive heard pre heating is not necessary. :confused:

[MXtras]

I preheat to 750F, weld, then wrap the area up in a welding blanket afterwards to slow the cooling. It's the way I was taught. I have raced several bikes that had frames that I had repaired and only had one weld fail out of all of them - that was in 1983! MX bikes have come a long way since then!

Wow. My age is showing... :o

Scott

[stringer bead]

I've also heard pre heating is not a requirement when welding thin peices but the smallest weld on this is going to be 1.5" I believe And the enitre fab is going to take something like 800lbs. of weld wire all together.

[TRG-42]

You really need to find out what the material is . I am not familiar with the trade name Chromalloy . to assume its a Chromium Molybdenum is not a good idea

You need the AISI/SAE spec

It could be a chrome alloy steel 5XXX , it may be a chrome moly ( 41XX ), or a chrome nickel moly ( 43XX and 47XX ), chrome nickel ( 3XXX )

Even in the chrome moly family preheat requirements vary more than 200deg depending to type of chrome moly

Once you know what the material is you can run the specs through a proper preheat calculator

The required weld metal varies drasticly as does preheat / interpass post weld etc

Since the welds are relatively large ( 1"+ ) you should monitor your interpass temperature

Lastly , information on welding thin wall chrome moly tubing does NOT apply to chrome moly plate, shafts, pressure piping etc

Once we know the material spec we can go from there

[MXtras]

Hopefully, this thread was not for a critical application - but you are absolutely correct in stating that the specific alloy needs to be stated for an exact set of procedures. However, just knowing the specific alloy would be insufficient. It's likely there is a print somewhere that identifies the entire welding procedure in detail. If not, shame on the company for wasting their money.

It's funny - not long ago, someone here flamed everyone on this board for always asking for very specific details on absolutely any and every topic, yet when 'we' make generalized statements to try to help out a member, it doesn't seem to work, either. Is there no winning here on this forum? Is everyone afraid of being smashed for giving a partial answer based on partial information?

I took this thread (right or wrong) as a general curiosity question and not a question about a critical application - hense the lack of detail by the thread starter. He doesn't have the details and therefore it's extremely unlikely that he has the responsibility of getting the job done. If this guy is responsible for welding a critical application with an expensive material, then shame on the company and shame on him for accepting a task that he was ill-equiped to perform. I seriously doubt that given the cost of alloy steel the company would have anything other than a certified weldor welding it. As a shop owner and an engineer, I sure wouldn't and know of none that would. I can easily understand where our thread starter heard this material refered to as "chromalloy" - as in chrome-alloy and had some curiosity.

I apologize for answering his generic question with a generic answer but I felt his question was fair game for a public forum just as I felt my response was appropriate. Shame on me, I guess. :confused:

Scott

[EvanK]

PM Bigger Valves his names Benny and he knows alot more than most about the topic, he should be able to help you out.

[90blackcrx]

Preheating is not needed in some cases, good link

http://www.lincolnelectric.com/knowledge/articles/content/chrome-moly.asp