410SS vs. 316SS vs. Something else? 3

[mxracer17788]

Hi all,

Just a quick question for all you stainless steel experts out there. We make a special type of tapping screw from 410 stainless because of its hardening capabilities and our requirement to produce a hardened drill tip. In addition, these fasteners will be used in external environments where corrosion is an obvious concern. We would love to use 305 or 316, but we are not able to achieve the high hardness in the tip that will allow us to drill through steel. My question is, is there a stainless steel alloy that can be both hardened by heat treatment, and offers the corrosion protection of 316? Obviously cost is the most important issue, but I'm open to suggestions.

Thanks a lot,
Don

 

[arunmrao]

316 is corrosion resistant,but cannot be hardened,also it is more expensive than 410. You can try some of the precipitation hardened stainless steels as an alternative.I am sure some might suggest 202 too.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[TVP]

Here is how Infastech & SFS get the best of both worlds:

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http://www.sfsintec.biz/internet/sfsinten.nsf/PageID/SX_RC

 

[mxracer17788]

Interesting read TVP, I will definitely have our manufacturing engineers take a look at this. I'm wondering how they attach the 1040 hardened tip to the stainless steel shank? Possibly friction stir welding? Anyway, that might work but I'm assuming cost becomes an issue at that point since 300 series stainless steels are much more expensive than 410. Ideally what I'm looking for is a stainless steel that is hardenable by heat treatment with a case of around 50HRC, but that is also more corrsion resistant than 410 and comparable to 305. I understand that the more alloying will decrease hardenability, but is there a happy medium somewhere?

 

[mxracer17788]

Also, I guess just another question: Why use 410 stainless steel to begin with? From my understanding, the corrosion resistance is not good at all. Anyone disagree?

 

[dgallup]

It is possible to harden 300 series stainless although not with most conventional methods. We ion-nitride 303/304 all the time. Makes a very hard but thin case.

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[mxracer17788]

On another note, is 410 less susceptible to stress corrosion cracking and/or hydrogen embrittlement when compared to austenitic and ferritic stainless steels? I'm looking for good literature on this subject and can't seem to find anything...

 

[metengr]

Martensitic stainless steels and ferritic stainless steels by virtue of their crystal structures are more susceptible to hydrogen embrittlement because nascent hydrogen atoms readily diffuse through these materials with low solubility and can result in embrittlement. Austenitic stainless steels have much, much lower hydrogen diffusivities and greater solubulity for hydrogen atoms in comparison with little affect on embrittlement.

There is plenty of information that can be found on this subject.

 

[EdStainless]

the trouble is that if you have a martensitic stainless it hardens by forming Cr carbides, this takes Cr out of making the alloy more corrosion resistant.
There are no common martensitic grades that will come close to 316 in corrosion resistance.

You can almost get there with PH grades (15-7 or 13-8) but I am sure that they are way too expensive for you.

If you are roll forming these you might get hard enough cold working a lean duplex stainless (2101, 2202).
They have a lot better corrosion resistance than 410 or 304 and they are much stronger than a 3xx alloy.
But they will only harden by cold work.

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Plymouth Tube

 

[mxracer17788]

Thanks met and ed, huge help!

 

[Guest102023]

Back up a little and start by defining all the properties necessary for your part.

 

[TVP]

I believe that the point is joined to the shank by resistance welding. Friction welding is generally limited to larger cross-sections and slower cycle times. With regards to Type 410 stainless, no one will argue that it has limited corrosion resistance. Some manufacturers even use coatings on top of 410 screws. Google Climashield for more info.