Compressive yield strength of 12L14? 1

[EdDanzer]

Has anyone done a compressive yield strength test on 12L14 or other free machining steels?

We purchase a product made with free machining steel that seems to have a low compressive yield strength leading to premature product failure. The manufacture does not think this is the problem even though a test buy an independent lab shows product failure.

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[CoryPad]

What condition? Hot rolled or cold finished bar? Compression properties should be the same as tension properties. Usually this type of steel is used for parts that only require that they occupy spacetime without concern for mechanical properties. Thus, a chemical composition (and maybe a hardness) are the only specifications. You can use MatWeb for basic information:

http://www.matweb.com

Regards,

Cory

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

 

[swall]

Ed, is the product failing in compressive loading due to splitting in the longitudinal direction? If so, the inherent lead and sulfur stringers are to blame, not just compessive yield strength.

 

[EdDanzer]

CoryPad,

The material is cold drawn round bar and the Brinell hardness is around 155.

swall,

The compressive loading is longitudinal to the grain and the load bearing area is a small ring.

How does a compressive yield test provide a different result than an actual part test? Or does the application require special consideration when choosing materials?

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[CoryPad]

Without knowing the details of your product, the potential difference between a materials test and a part test would be uniform stress (cylinder for materials test) vs. nonuniform stress (actual part). The secondary microstructure phases (lead and sulfide inclusions) and the anisotropic properties (cold drawing) result in a material that does not necessarily behave like a continuum, which complicates stress analysis. So, the final application may require special consideration when selecting materials and their treatments.

Regards,

Cory

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

 

[unclesyd]

The material 12L14 was sold under the name of Ledloy originally made by Inland Steel, which is now Mittal. I've been looking around for numbers an have yet to find anything other than it's equal to something, not real. If I recall correctly Ledloy has very poor elongation, 10-12%, and the material for lack of better description when if fails it shatters.
If the failures are in a relatively thin section, as stated above the lead stingers could be participants in the failure mode. Thin section meaning less than 1" thick. We found that in thick sections, over 1" the lead is less of a problem unless you are heating and cooling the component.

The material has a ASM spec and an SAE spec.
The specification is ASM SA176 or SA 227 Ledloy, it has several grades depending mainly on the chemistry.
I think the SAE 12L14. See the link below for additional standards

Sure wish I had kept all my old product brochures.

We have had major problems with leaded 41L40 and non-intentionally leaded A2 tool steel. During the initial failure investigations of all failed components we could fine no smoking gun pointing to the lead stringers in metal. When we started examining the base material I was able to find incipient cracking emanating from the lead stringers in both materials. The cracks were about half as long as the stringer and at times were found on both ends of an elongated stringer. The cracks were only visible at 900X on a light microscope. In both materials it appeared there was orientation based on the rolling direction, which would make the material directional. How the component was stressed could make a big difference in behaviour of same.

http://www.acindar.com.ar/eng/prod_2a1_corte_alambrones.asp?menu=2&submenu=2.1

Anecdotal:
Why I can't find the compressive strength of Ledloy.
I left the bulk of my old product data sheets in the lab when I left work and soon after I left they had a summer intern go through the files and keep what he considered relevant. Guess what. When I asked why this was allowed because there were still a lot of components made from the various materials,the response was that all this information was available on the Internet.

 

[Maui]

The lead and sulfide stringers are not able to support significant applied stresses when the parts are tested or placed in service, and effectively act as "holes" with respect to the applied stresss. Due to their geometry, size, and orientation, they can also act as stress risers leading to premature crack formation as described by Unclesyd.

EdDanzer, can you provide us with more detailed information about the product that you mentioned? What exactly is the product? What are the material specifications that the 12L14 was ordered to? Specifically, what was the required minimum compressive strength contained in the material specification? And what is the compressive strength that you have measured on this product?

Maui

 

[EdDanzer]

Unclesyd,
I can relate to missing old literature. At the end of 2000 I made a business change decision and threw out much old information that I didn’t think I would need or could find later if I did need it. Large mistake, much of the in depth data is not published or free to access on the internet.

Maui,
The product is a floating nose hydraulic cartridge valve. The threaded body is 12L14 and it has hardened nose piece that presses against it. The shoulder bearing area is a small ring which amplifies the “holes”. The initial .002” of compression happens at about 72,000 psi.

We have observed unusual low compressive yield stresses relative to tensile strength with several materials over the years in hydraulic and off highway components.

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[deadrange]

All:

Please do not forget teh 12L14 is an semi-killed grade, and extremely coarse grain. As for the low compressive forces to failure, I have to agree. This grade with its high sulfur and lead compositions was never designed to withstand serious forces. It was designed more for its ability to machine. In fact it is still the benchmark for most machining comparisons.
There have been mutliple attempts to mimic the improvement lead brings to the machining characteristics of the material. The latest iteration that I remember is Tin additive. I think it was developed out to Pittsburgh. Also Tellurium is used for improved machinability.
Like the posts above, it is likely that the lead/sulfur stringers are likely the source of the failure. Depending on the steel mill, lead is added either to the ladle of the tundish. I don't believe anyone is putting lead into the mold as it has more strings problems than the other two methods.

 

[TVP]

I am assuming that the hardening process is a case hardening operation, either carburizing or carbonitriding. It is possible that the material adjacent to the surface has residual tensile stresses and a very large grain size, making it weaker than the tensile strength given for a cold-drawn bar.

 

[EdDanzer]

The threaded body that fails is not heat treated. The nose part that is heat treated (unknown material) slides into the 12L14 part and shoulders on a circular area of 1.095” ID X 1.154” OD. Our current modification is to place a heat treated flat washer between the 12L14 part and the HT nose part.

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com