We sometimes face with a wire rod defect (hole at core of cross section and accompanying two fins on the surface) in high and also low carbon steels having chemical compositions as below. The length of the damaged section is between 30 and 70mm.

In one coil, there may be only one or more defects (not periodically).

D65: 0.63-0.68%, Mn:0.45 - 0.65%
20MnB4: 0.18-0.23%, Mn:0.90 - 1.20%

We have 10 Stand V Type Ashlow Block Mill.

Any ideas?

Hi there mozkarakoc;

Could you please tell us how fast the rod is moving when these defects occur. I was just wondering what the time period was when these 30 to 70 mm defects are created.

Thank you

Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com

Hello again and thank you for the information and the nine photographs.

I was amazed when I saw the occasional smooth sides and the right angles in the voids. I have never seen anything like that before.

I have forwarded your information and pictures to the moderator of this Ferrous Section. I am sure he will provide you with some information shortly as he is very experienced and qualified.

Personally I have no answer for this very unusual problem. I would imagine however that the external fins are created because the steel rod is of constant weight/ volume and the volume of the fins closely approximates the volume of the void inside the rod.

I presume your 10 Stand V Type Ashlow Block Mill is performing a hot rolling process.

Regards
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com
WAI Moderator - Electrical and Supplies and Equipment Sections

The problems of holes or discontinuities on the section of the rod, originated at casting the ingot or billet before it is rolled.

- If the route is by ingot, it could be caused by the difference of the cooling temperatures along the ingot or by inclusions, mainly of refractory components.
- If it is via continuous casting, it can also be caused by inclusions of refractory elements mainly at the tundish.

Surface defects are caused by defective rolling practice. These problems are not common and must be from the rolling mills.

Eduardo Anaya
Senior Consultant
INDEPA S.C.
Mexico City
Tel(011-52)555-407-7451
This email address is being protected from spambots. You need JavaScript enabled to view it.

The mentioned defects are made on casting steel ingots or billets, can be due to differences on cooling temperatures along the ingot or the billet or made by inclusions mainly of refractories used to insulate heat.

The surface defects are caused during rolling by damaged guides or rolls.

The above mention defects are uncommon for must of modern steel mills.

Eduardo Anaya
Senior Consultant
INDEPA S.C.
Mexico City
Tel(011-52)555-407-7451
This email address is being protected from spambots. You need JavaScript enabled to view it.