Scratch on Rebar 2

[hkiremitci]

Hi everybody;
We are producing reinforcing steel bars. We have some scratch on rebar rib. we saw scratches on 3 or 4 ribs on one 12 meter rebar. Billet does not have any defect like crack. Can you explain reason of this cracks on ribs? Thanks in advance

 

Pictures?

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[hkiremitci]

These are bars.

 

[hkiremitci]

These are some photos from previous stands.(before becoming rebar)

[img

https://res.cloudinary.com/engineering-com/image/upload/v1599753044/tips/2020

[img

 

[hkiremitci]

 

[hkiremitci]

I beleive that somehow, billet surface is tearing in preparation pass and these teared surface goes another pass. at the end we saw this teared surface on rebar. Because when we saw these cracks on rib and also on core, we changed preparation passes. After that % 90 of problem is solved. At least, we did not see any crack on core. Now, we saw these cracks on steel before becoming rebar.

 

The raw material may come with incipient flaws that only manifested under extreme working, or it may be in a more hardened condition where it has less ductility than expected.
At the other extreme, the tooling is at fault. Running a different heat of material would answer this.
Sounds as though you are on the way to solving it though.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[hkiremitci]

dear ironic metallurgist
can you explain it in more detail?

 

[kingnero]

If you are using european designations, is this DE 500 BS, BE 500 TS or BE 500 S ?
If not, can you tell the production steps?

 

[hkiremitci]

it is st37 steel. C 0,18-0,22 , Si 0,15-0,18 , Mn 0,55 - 0,60

 

[gtaw]

Most like originated with the original stock from which the rebar was subsequently rolled. Most likely appeared as a seam on the surface of the raw stock and still appears to be a seam on the finished rebar.

Best regards - Al

 

[hkiremitci]

it is related to billet or rolling process?

 

[nouredinne]

we face same defect
any suggestion?

 

[blacksmith37]

The rebar has been very heavily etched or pickled to bring out these stringers which are not unusual in ordinary , relatively dirty steel. Normally this degree of etching would be done to evaluate steel cleanliness , not routine pickling to remove scale.

 

[nouredinne]

Hi
If you can explain pleaze
blacksmith37

 

[blacksmith37]

When you macroetch you are probably going to find inclusions and stringers. Then you need to decide if they meet specification, if there is one, or decide if they are acceptable for service. T

 

[nouredinne]

Thank you
blacksmith37

 

[mfgenggear]

sure a lot parent material defects, section and review. see if it has internal defects as well. hopefully not

 

[mrfailure]

I would make 2 micros from one of the bars, one longitudinal and one transverse, and look at them in as-polished as well as etched conditions to see if there are internal (as opposed to surface) cracks, whether they are consistent with seams in the original billet, and what kind of microcleanliness this rebar really has.

 

[gtaw]

Railroad rails are often rerolled into concrete reinforcing bars. The track head is separated from the "tee" and is used for rerolling. Any notches, oxides, etc. would be present in the reinforcing bar. I wouldn't be surprised if there wasn't a You-Tube video showing the process.

Best regards - Al