Cast crowns and lugs, is the material strength compromised by overheating/

[claritycycler]

When removing and replacing tubes or fork blades from cast crowns or lugs does the structural integrity of the casting suffer from possible overheating? Is the cast material effected the same as tubing if overheated? Is there one particular alloy commonly used in producing these cast components?

thanks, Brian

[e-RICHIE]

As with anything, it's about your skill level. If you reach a point where you're uncomfortable with the heat, the answer is yes something is affected.

[Andrew R Stewart]

When using heat to pull pipes out of sockets make sure you know how the pipe was located when first brazed in. Was there a pin?

I have recycled a couple of crowns over the years but these days don't. The cost for a new crown (and steerer) is far less then that of your reputation or face. Andy

[claritycycler]

Still looking for the alloy type used in investment cast crowns and lugs, anybody have that info(gray, white, malleable, etc)? I've google searched but haven't found that info.

thanks, Brian Clare

[Andrew R Stewart]

This info could be considered as propriety information and any manufacturer might not divulge it especially if they knew that the intended use was not within their design plans (recycling stuff). How are you at doing the spark test? I would contact the manufacturer directly (HJ is both an end user supplier and the designer/manufacturer, they might be the only one who is willing to talk with a builder). BTW your material terms are not what I would use in this discussion, they show your lack of metallurgical knowledge and red flags might go up their poles. You might also contact steel casting companies for what they typically use and start your education more broadly before going to a bike specific caster. Andy

[claritycycler]

... You might also contact steel casting companies for what they typically use and start your education more broadly before going to a bike specific caster. Andy

Andy, I'm asking the questions because I don't know(still) what alloy(s) is used in lugs/crowns(after spending a couple of hours google searching and wading through technical papers on cast mtsl and processes). Perhaps you can point me to a location/site that has the knowledge I'm looking for if you know of any, or if you know the casting alloy(s) used. I don't want/need hand holding, just a source for an answer to a seemingly simple question.

thanks,

Brian Clare

[e-RICHIE]

Brian - the material used in my castings is SCM21.

[claritycycler]

Thank you Richard.

Brian Clare

[claritycycler]

Scm21 composition:


Brian Clare

[e-RICHIE]

Scm21 composition:

If it matters at all, or affects whatever you're doing, I have brazed frames for 45+ years and never cared about what steel the parts were made from. No snark. That's brutal honesty. The integrity of the bicycle comes from your skills and assembly details, not the material.

[claritycycler]

It was a simple matter of curiosity, thats it. I just wanted to know what the material/alloy is and its properties, not doing anything with the information to complete any specific task.

thanks, Brian Clare

[Andrew R Stewart]

Brian- Sorry if I came off as snarky. But I did try to give you a direction to find your answers. Few here contract their own castings (Richard being one who does). I would expect you'll find that the properties of the various steels used in cast bike frame components fall into a fairly narrow range of real life qualities. Andy