Calcium in Steel 1

[redpicker]

I know that calcium is intentionally added to steels, particularly continuous cast steels, to improve castability.

I know it can also be used to control the morphology of the non-metallic inclusions, particularly the Manganese Sulfides. This shape control can improve the transverse ductility properties.

Are these two benifits concurrent? That is, will a heat of steel that as been calcium treated for castability also see the benifit of inclusion shape control?

I assume a chemical analysis would show the calcium. What levels of calcium would one expect to see in the chemical analysis of a calcium treated heat?

rp

 

[EdStainless]

No, the benifits are not always concurrent. Depending on overall composition you may or may not see both factors.

No, steel treated with Ca will not show it in the analysis. Since it is not a specified element and it is not added to change the properties it is not reported (along with AL, Ti and a few others).

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http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[metengr]

Some additional information on the subject;

http://www.shieldalloy.com/calciumpage.html

 

[dbooker630]

Typically when called for in a material Ca will run .0005-.0015 on the mill cert. Calcium, aluminum and the other refiners like Cb, V, Ti will be reported by some mills but not all.

You will have to specify what is to reported or take your chances on what is in the warehouses.

The appearance under the microscope is a CaS compound surrounding an oxide nonmetallic.

 

[redpicker]

Thanks metengr, that was exactly what I was looking for.

EdStainless, I am dealing only with low alloy steels, if that would affect your response.

We purchase and comsume heat lots from the mills, so I can pretty get whatever I ask for, both as composition and what is reported on the certs. Steel mills, however, can get somewhat tight-lipped when I ask this information directly, however, since whatever they tell me holds the possibility of finding its way into my specification (they don't like any special requirements).

What I have found out (and is not included in the link metengr posted) on my own is

1) The sulfur really needs to be below 0.015 for the shape control to be effective.

2) Ca treatment is detrimental to bearing life, so its use is restricted in some applications

3) Ca treatment is also detrimental to machinability, again, a reason to restrict its use.

If someone can confirm or argue these points, I would be interested in hearing your comments.

Thanks,

rp

 

[metengr]

redpicker;
See below,

1) The sulfur really needs to be below 0.015 for the shape control to be effective.

See paper 21

http://db1.wdc-jp.com/cgi-bin/isij/guest/list1.cgi?list=199699

Some limited information

http://www.us.cbmm.com.br/english/sources/techlib/report/metall/metall.htm

2) Ca treatment is detrimental to bearing life, so its use is restricted in some applications

See

http://www.scielo.br/scielo.php?pid=S0370-44672004000300008&script=sci_arttext

 

[arunmrao]

A google search and some browsing produced a few interesting articles on Ca metallurgy in steel making. They may not have a direct answer to your question,but it can start a new thought process. I hope it is useful.

Influence of Calcium Treatment on Castability of Continuous Casting Molten Steel

http://www.baosteel.com/english_n/e07technical_n/tech020702.htm

Influence of Calcium Treatment on Castability of Continuous Casting Molten Steel

http://www.corusgroup.com/.../research_and_development/papers/paper-some_aspects_about_the_behaviour

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Interaction of Alumina Inclusions in Steel with Calcium-Containing ...

http://doc.tms.org/ezMerchant/prodt...0512-885/$FILE/MMTB-0512-885F.pdf?OpenElement

 

[TVP]

redpicker,

Daido has developed free-machining steel grades that do not contain lead. They are calcium treated together with titanium, with sulfur contents significantly higher than 0.015% (0.050-0.10%). The following SAE paper is a good English-language description of the technology:

http://www.sae.org/technical/papers/2004-01-1526

Corus and Nippon Steel also have developed calcium-modified steels with high sulfur.