430 stainless steel tested per ASTM E45 1

[vti]

I am looking for a source of 430 stainless steel bar, approximately 1.5 inch diameter that, when tested to ASTM E45, Method A or D, must have an inclusion rating of 1.0 or better, (2.0 may be acceptable). I have been told by one source that, historically, the only way to achieve this rating is by vacuum melting. I have been unable to find a source for 430 vacuum melt material. Another source has stated that recent improvements in casting techology do away with the need for vacuum melting to meet the inclusion rating.

The material will be used to manufacture weldments of 304L VM and 430. These are then machined and ultimately used in coaxial solenoid valves for propellant control on satellites. The weldment is considered a pressure vessel and must be pressure tested to verify that leakage is less than 1x10-6 sccs helium at pressures to 1500 psig. We currently have about a 10 to 25% loss rate due to leakages in the 1x10-5 range across thin, 430 walls (around .04 to .06 inches thick). We would like to use a better grade of 430 to reduce our loss rates. Also, and probably more importantly, one of our customers is imposing a requirement for the use of material with the above stated inclusion requirement.

I have the following questions:

a) Can anybody comment and/or provide background info on the need or lack of need for vacuum melt to meet the inclusion rating in 430?

b) (The million $ one) Can anybody provide me with information on possible sources for this material.

Thank you very much and I look forward to your questions/comments.

 

[EdStainless]

We manufacture tubing in 430. It is AOD melted and it is much cleaner than a stabilized alloy like 439. That said it still has a fair amount of inclusions.
The real key in your case is to find material that has been heavily cold worked to break up the inclusions.
Are you concerned about leaks in the axial direction or radial, or is it the weld? I have seen a lot of axial He leak issues with stainless bar, even high purity.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[mcguire]

vti
Cleanliness of a stainless is not better with Vacuum melting than with the normal arc melting/AOD refining that nearly everyone uses. Cleanliness comes from the absence of indigenous inclusions, mainly oxides and sulfides, and exogenous inclusions, mainly oxides, which come from refractories,slag and re-oxidation during handling the molten steel.
Indigenous inclusions are essentially eliminated by normal silicon/manganese deoxidation, in which oxides formed above the melting point are removed with slag. The same is true for sulfides. Specify 0.002% sulfur...anyone can achieve this level.
Lack of exogenous inclusions comes from good steelmaking practice. You don't have many good choices if you're in the US. Cartech is the best bet for 430 bar.
I do question the choice of 430, a generally crude grade of stainless and one which forms martensite when welded. If you stayed with austenitic, you could get excellent material from Trent or Rath.

 

[israelkk]

I understand that the 430 is for the magnetic parts of the solenoid and therefore should be solenoid quality grade. The best was to avoid contact of the fluid with the 430, however, that depends on the design of the solenoid/valve.

From my experience we have not experience such problems when used 430 for similar designs. I think your best bet will to contact Carpenter

http://www.cartech.com

and ask them. I assume they even will agree to manufacture solenoid quality 430 VM if you order a minimum quantity (I assume 1000 to 5000 lbs) which is cheap concerning the time waste, and the high cost of all the failed tests and products.

 

[vti]

Thanks for the info guys. To reply to some of your comments:

EdStainless, the leaks are generally axial, about a 5/8 inch from the part centerline. We have had a very few at the weld joints. FYI, I will be contacting your company about 430 tubing. We make a lot of solenoid housings from 430 bar stock. This requires a lot of machining. Starting with tubing would be a lot easier. We have looked in the past for 430 tubing with no luck. It's nice to solve one problem when working on another. Thanks.

mcquire, thanks for the input. FYI, we need the 430 for magnetic properties.

israelkk, we cannot avoid exposure of the 430 to the fluid media because of the coaxial design. Typically, we also do not have a problem because we are able to keep wall thickness over .1 inch. We only see this on designs with thin walls, about .05" or less. Our purchasing agent (non-technical) has discussed with several distributors with little luck. So far, only one distributor has quoted, and that is for 40,000 pounds. At our rate of usage, that will last for several generations! They also will not disclose the mill, which makes us more than a little uneasy. Now I am trying to help her by going to the technical people. I will be using the carpenter website, along with others.

Thank you all for your input.