continuous casting of steel - jerking 4

[alloy33]

Hi all, I would like to know if somebody belong to this forum has experiences about jerking problems on continuous casting machine for steels.
my questions are:
1. if you have jerking, a part to depend on the steel grade to be cast which may "stick" more or less into the mould, which are the other factors from which jerking depends?
2. how could you avoid jerking if you have it? on which casting processing parameter it is more appropriate to operate?
3. do somebody have some guide line to avoid jerking problems?
thank you very much for all your help.
best regards,
Alloy33.

 

[NickE]

You might wnat to try looking this one up in a book on continuous casting... ASM/TMS certainly has one...

nick

(I first thought you might be a student in college, on second read you may just be an enquiring mind..

Likely has something to do with the caster powder, the vibration frequency of the mold, the coolant flow of the mold, and the magnetic stirring in the tondish)

 

[mcguire]

NickE is correct. Sticking is real bad because it is the steel trying to tell you it's about to have a breakout, which you don't want to be real close to.
Get your mold powder vendor to bring in their technical rep. And get very strict on your practices. You will need to show the expert thr range of the key operating parameters, and especially where they are when sticking occurs.
This is a real well known problem that has already been solved. Go to the people who know. If your mold powder vendor can't solve it, change suppliers. Unless, of course, it is the result of imprecise operating management.

 

[umreng]

During continuous casting, there should always be a lubricant filled gap between the mold surface and the strand surface. The lubricant may be mold powder in the case of slab casting or a special liquid (rape seed oil) in the case of billet or bloom casting. The lubricant is an excellent heat conductor to carry the high flux of heat out of the solidifying strand. Different lubricants may be indicated for various casting conditions in the same machine. During withdrawal of the solidifying strand, oscillation motion between the mold and the strand should be continuous so that the first area of solidification of the shell of the strand can periodically (quickly) move with the strand to expose a new area of the liquid metal to commence solidification. The jerking activity indicates that the oscillation is being impeded by some factor. The factors which might adversly affect smooth oscillation include: strand bleeder, solidification shrinkage, mold taper, oscillation frequency, oscillation amplitude, oscillation waveform, mold cooling rate, mold liquid level system malfunction, secondary cooling rate, tundish temperature, superheat temperature, mold alignment, oscillator backlash, lubricant viscosity, casting speed, withdrawal equipment misalignment, footroll alignment, computer malfunction, etc. The possible factors related to steel grade are few, but important. The key to avoiding jerking or sticking is to identify the root cause and eliminate it. Keep in mind that there may be more than one factor involved. Inspect the cast steel after cooldown to see if there are any clues as to the sticking mechanism. Check alignment and strand condition to a very high standard. If you consult a casting expert, be sure and identify the type caster completely: Mold size, curved mold/straight mold; mold taper (single/multiple); mold corner radius; mold material; hydraulic/mechanical oscillator; Casting machine manufacturer, age of equipment, type of lubricant and feed method; mold water velocity, type of withdrawal system, mold level detection system type, etc.

 

[NickelMet]

I won't disagree with what has already been said, especially in the last post. Here are some further sources of information though:

web:

http://www.aist.org/

books:
1. "Continuous Casting" Volumes 1-10, published by ISS (now AIST)
2. "The Making, Shaping and Treating of Steel, 11th Edition - Casting Volume", published by AIST

It isn't always easy solving sticking problems, just remember not to change too many variables at a time. Keep good records of what you do, when you do it, and what the outcome is. And one thing to do is to look at your history, prior to the onset of a problem. If you have tracked various caster parameters and have a good, reliable history, a review of the current conditions may provide the "Aha factor" to solving your problem.

In my previous life as a casting metallurgist, there were four factors that were predominately the cause of sticking at our caster: temperature, casting speed, mold lubricant flow, and shrouding backpressure. These were the issues we usually addressed first. Also, we found it critical that the cooling water side of the molds be free from any scaling. (Water conditioning was critical and each mold was tracked to a specific cleaning schedule.) Just a small word from my experiences.

Good Luck!

~NiM