Slag Inclusions and Low Carbon Steel

The inclusion content of the steel should be checked from billet or bar samples at time of manufacture. ASTM_E45 is the proper schema.

Actually, a careful reading of your query specifies slag inclusions, not "nonmetallic inclusions." and you may be at a customer company checking product, not semifinsh or inprocess at the mill. So I will re-frame my answer.

Your phrasing "slag inclusions" implies that the casting process you are using may be inferior to todays commercial processes with proper damns and weirs in tundish and electromagnetic stirring and shrouding and slag carryover control and mold level control.

So answering with regard to gross deleterious exogenous slag inclusions, the answer is that the heat treatemnt itself will not really change them, however the hot work of rolling will infact extend them dimensionally in the direction of the hot work, while reducing their diameter by the same ratio as the reduction of hot or cold work.

A 6"X6" square billet rolled down to 1" round has a reduction ratio of 45.8:1 so the transverse measurement of the slag inclusion will be approximately one forty- fifth or 2.2 percent of its original as cast diameter.

The 'hardness' of the base metal is not an issue in this case.

If checked after heat treatment, i would argue that the inclusion may be more fractured due to volume change forces of metallic phase transitions, but you said low carbon, (why would you heat treat low carbon steel?) and didn't specify the heat treatment, so your use ofthe term heat treat may in fact mean only just an anneal and no phase change...

At any rate, heat treat will not change the mass nor presence of the slag inclusion.

Hope this helps.

milo

Thanks Milo.

We are carburising & hardening low carbon steel in Sealed Quench Furnaces.

We are manufacturing gudgeon pins. The idea is to get hard surface with

sufficient toughness in the core zone. Before processing in the furnace; the %age

carbon is 0.2 whereas after processing, it rises to 0.8%.

Hope this satisfies your curosity.

Yes, I see. The carbon rise is only on the OD where it diffuses in ; A mid radius or center analysis will be the original %.

Hope my response was helpful. Thanks for the followup.

milo