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Found an answer in part in an article on pearlitic wire. Mainly Hall-Petch strengthening between the pearlite lamellae. Fracture and shear of the cementite occurs, but it's not the primary contribution to strength. - it does initiate microvoids which can reduce ductility. I was going to link...

The mark will probably polish out. If it doesn't and it's deep, then cause for concern, but I'm guessing it wasn't installed looking like this. Modern steelmaking processes aren't that dirty that you'd have an inclusion or material fault of this scale.

Hard to tell. You'd need to see the full article. I read the 0.9 f_ctm as being 10% factor of safety in the loading. I have no idea what the 'ctm' stands for in this instance. It just indicates to me that a strain from 0.11 to 0.15 occurred with no major increase in stress (ie...

Thanks Dhurjati, I actually had a copy of Dieter here as well - looked it up as per your suggestion, but it covered the Hall-Petch equation and general strengthening explanation for grain size modification. Have you any idea of research that quantifies the strengthening mechanism in a plain...

Hi All, Am an honours-qualified Materials Engineer with 15 years experience, prior to teaching high school students since 2002. The content of the course I teach is at the first-year university level, excluding calculus, delivered over 2 years. With COVID-19, I'm teaching my senior class via...

I don't understand how the rolling process can introduce voids, unless there's delamination in the core material occurring due to friction. Would I be correct in assuming that the issue with residual stress is stress corrosion cracking as blood is fairly corrosive due to the proteins/enzymes...

Boltslinger, There are a lot as outlined above. Key point that hasn't been explored is the environment and the stress loading. Is there a cyclic stress as well? You probably should be looking at creep resistance also. Is the environment oxidising, reducing, acidic...

Confused, I interned for 7 years as I did a degree part time. At the end of the day, when you enjoy your work it ceases to become work and then you learn easily and are successful. Engineering depends upon continuous learning as you know. Ed's advice on being able to present and listening...

Just a quick dot point not mentioned above. This fracture pattern is intergranular fracture above along the prior austenite grain boundaries (which is where the sulphide stringers form) You will also see this pattern in weld sensitised areas of rolled steel. Cheers,

Hi again, That paper for download I gave you last time has this info. Was it 550C for reasonable scale formation? As with all metallurgical processes, it's time and temp that relate to reaction - typical arrhenius reactions. Cheers,

Careful, Just to add (and I'm aware that I'm probably telling you something you know already) the scale is ceramic and abrasive - it can pick up small particles of material from the die. AF

Hi Careful, There's a lot here that work with/specify stainless daily - I'll defer to them. To answer the question "Why does the scale rust" - Scale is, by definition, the oxide layer. Either this oxidised stainless has picked up chloride/sulfur compounds during fabrication, and you're seeing...

Tolerance of 1.4 microns - 2 microns. This is getting towards F1 tolerances - the mills that grind these are in a climate controlled room with coolant at a specific temperature. If you know the heat profile in the ball, you could use standard coefficient of expansion, but to be honest, for...

Depends upon the property you're looking at designing against ornerynorsk. The advice above is spot-on. eg: if it's a beam in a walking beam furnace, max service temp = 300C. If it was scale resistance, it'd be higher and dependent upon composition.

No problem - Hope you get to the bottom of it if needed. We used to leave a chimney in a cement kiln open to give a working draft to those in the kiln during repair - similar sized chimney @ 60m The only way we could work at the back end of the kiln was to shut the dampers completely to avoid...

Just noticed you said you were an intern. I did a quick google search for some papers to help guide you - I was a trainee metallurgist (similar to your internship) in our local steel company - degree was 7 years part time while I worked in the trade from the age of 18. Here's two immediate...

Former cold mill and pickle line technical assistant (process metallurgist) in a 1000tpd plant in the late 80's/early 90's when I finished my degree so knowledge is a bit dated. Easiest option is the trial as mentioned above, but you need to find a way to measure it. While time at temperature...

Massive draft - I think from memory 10"WG at the bottom of a 60m vertical chimney, which would be the same as your case with a 60m height. I haven't got my chemical engineer's handbook handy at the moment. Was the defect along the whole weld? AF

Horizontal, not flat - thanks It's almost as though there's some sort of pressure buildup on the other side of the weld that's blowing the metal out of the weld pool was the only thing I could think of for the consistent size of the 'extrusions' - I've got a basic welding ticket and used to...

Hi Lyrl, I read original post as items not being in service and the spalling post pressure test immediately. Whilst I haven't read the link on case crushing above, in the past, I had issues in the past with a maximum stress concentration during pressure application being at the depth where...