1018 CRS 3" x 4" Bar failure during rolling

[rkurtz61]

Hello all,

We have a job to roll four 3" x 4" x 12' 1018 CRS bars to 97" IR. There are two heat numbers (3 bars with one number, 1 bar with one number) which were never marked on the bar by the supplier as MTRs were not required. The first bar rolled perfectly. The second bar sheared approx. one foot into the rollers on the first pass, prior to any real pressure being applied. Third bar rolled fine. Fourth bar sheared approx. two feet in on the first pass with slightly more pressure then the first bar that failed. Our roller operator is very experienced so I've taken operator error off the table.
I contacted the supplier and immediately he began to tell me we should have orderd hot rolled as CR is harder and more brittle, however we've used 1018 CR bar of this type and size before with no problem. My question is, should we go with HR in the future (and for replacement material for this job) and if so, what are the critical differences in properties between 1018 HR/CR as far as rolling goes. Any help would be greatly appreciated.

 

[unclesyd]

Do you have the hardness of the the 4 bars?

I believe HR will be OK as the only thing you really gain is in the bar finish. If you can get the HR in TGP it should work better.

I've always taken that rolling CR mild steel at or above Rb 80 was a gamble. We always like to roll in direction of plate forming roll, parallel to the mill rolling direction, which is impossible in rolling a hoop.

 

[CoryPad]

The formability of steel is dependent on many factors. In general, hot rolled steel should have more plastic strain capacity than cold rolled, but quantifying it requires actual data regarding the material and its processing history. It would be best to work with your steel supplier and quantify how much strain their material can provide vs. how much strain is required to form your part.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[rkurtz61]

Thank you gentlemen, I appreciate the info. The originl bars were under no or very, very little strain when they broke and that's what I thought was odd, however our supplier has provided replacement HR bars and we will be rolling them tonight.

 

[unclesyd]

Please let the forum know what the results are. This may help someone else in the future.