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Stainless Steel Replacement

08/26/2009 6:56 AM

Ladies and Gentlemen - I am looking for some assistance / advice. I currently have a project we are working on that has machined Stainless Steel, Steel, and Aluminum details in it. I have been tasked to reduce cost, without reducing strength or cosmetic appeal of this project. We have determined that we should be able to remove the Stainless Steel material and replace them with a standard grade of steel, then electroless nickel plate them and apply a chrome plating over that. While this will change the look of the part it will not change it for the worse.

The real question comes in what grade of steel would be a suitable replacement for 303 and 440C Stainless steels? I have contacted our steel supplier and they recommended that i look thru there book at the steel grades and pick one that will work for this project. And i suppose there are some of you that will say the same thing, which is fine. But i am just looking for a suggestion, or starting point. Believe me, i will investigate to the "nth" degree any recommendation.

Has anyone else had to do this same kind of cost cutting process and what material did you find to be the best substitute?

I look forward to you suggestions / comments.

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#1

Re: Stainless Steel Replacement

08/26/2009 8:32 AM

Hi there.

You mentioned you want to replace 303 or 400 ss for plain steel. Alright, if corrosion resistance is not an issue.

By the grades you mentioned, you are not dealing with high strengh or high temperature resistant variations (300 series are austenitic and 400 is ferritic, so not so critical in terms of mechanical strengh). SAE 1020 would perform in my opinion, and is by far one of the most inexpensive ones. Be sure to choose the correct raw material according your geometry (square or round bar, extruded or cold formed, etc) because this will make a really big difference in the final result. In low carbon steels, prefer cold formed ones, because, as you may already know, they will benefit from the finer microstructure for higher strengh and toughness.

Now, about your plating...

You mentioned you are supposed to nickel plate and chrome plate. I have dealt with such procedures, but I have always seen this double-covering only when the chrome plate thickness would be higher than allowable for a consistent plating. So, I'd also go for designing a product with final dimensions compatible for plating only with chrome, with significant reduction in time and cost of manufacture.

BTW, could you give some more details about the parts so we can check out what is coming?

Regards.

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#3
In reply to #1

Re: Stainless Steel Replacement

08/26/2009 9:18 AM

Thanks for the suggestions. This was kinda what i was assuming, but it is always nice to get confirmation. As far as details of this project, i really cannot give much information out as we do not own the product, we are a contract manufacture who will do a little design from time to time if our customer request it. What i can tell you is that is it a medical device that makes the nurses jobs a whole lot easier, and i hope none of you will have an experience where this will need to be used

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#8
In reply to #3

Re: Stainless Steel Replacement

08/27/2009 12:34 AM

In this case, just be sure it will never contact the patient, and no blood or other body fluids can spill over the stuff. Because chrome is not good for corrosion resistance in agressive media - humidity and solutions are very prone to attack it, mainly in the vanishing areas. If this is a possibility, I really feel sorry to say that you must go with an austenitic stainless steel. Even aluminum should be avoided. You cannot imagine what melt "blue ice" can do in an aircraft structure...

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#13
In reply to #1

Re: Stainless Steel Replacement

08/27/2009 7:28 AM

Too quick with an answer, my friend... He wrote 440, which is a martensitic steel, so it might be critical in terms of mechanical strength.

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#20
In reply to #13

Re: Stainless Steel Replacement

08/27/2009 8:02 PM

Nah... he mentioned 303. No way of being critical in mechanical strengh. But the fact that it is somehow used in a medical environment suggest that austenitic ones are desired...

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#2

Re: Stainless Steel Replacement

08/26/2009 9:01 AM

IF YOUR COMPONENT IS FLAT LIKE TUBE SHEET IT IS ADVISABLE GO FOR CLADDING WITH CARBON STEEL AS BASE. FOR OTHER SHAPES TRY THE OPTION OF RUBBER LINING.

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#4

Re: Stainless Steel Replacement

08/26/2009 10:26 AM

Mein Gott! If you're making anything medical, be very, very careful of chrome. Is this subject to FDA approval?

TVP45, posting anonymously.

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#5
In reply to #4

Re: Stainless Steel Replacement

08/26/2009 10:38 AM

We are testing for UL acceptance but i dont know that we have to do anything with FDA....no patient contact so i think that clears us of that requirement.

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#11
In reply to #5

Re: Stainless Steel Replacement

08/27/2009 3:24 AM

I suggest leave out the chrome and plate with nickle only but subject to summary polishing only. Nickle cleans up well and with a little polishing most will assume it's chrome anyway.

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#6

Re: Stainless Steel Replacement

08/26/2009 11:30 PM

Another question: How expensive is the thing your making and how long do you want it to last once it is purchased ?

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#12
In reply to #6

Re: Stainless Steel Replacement

08/27/2009 7:17 AM

The part is selling to our customer for around $5000, what they are selling it for i am unsure. The price is quite reasonable for what it is doing

Lifecycle is expected to be 3-5 years.

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#7

Re: Stainless Steel Replacement

08/26/2009 11:56 PM

It sort of depends on what fabrication processes you use on the 303 stainless. If you mill, drill, or cut, you may want to use one of the leaded steels for enhanced machinability. If you bend the steel, you must determine whether your selection can give the required bend radii. I don't normally see chrome over electroless. The two common corrosion resistant coatings we use are chrome over copper, and plain electroless nickel. As far as the 440C is concerned, this steel is often selected because it can be hardened. Many knife blades are made from it. If you require hardness or wear resistance, you might think about carbon steel, alloy steel, or tool steel. Of these, carbon steel is likely the lowest cost. Selecting a corrosion resistant coating for carbon steel will depend on the envirnment it must live in.

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#9

Re: Stainless Steel Replacement

08/27/2009 1:39 AM

If esthetic is not the issue better corrosion protection can be ensure by thermal spraying aluminum on steel structure. Refer http://en.wikipedia.org/wiki/Thermal_spray

Chromium plating is hard and brittle almost certainly have high population of invisible micro cracks, a desirable property where due good lubricity wear resistance is ensured like in piston rods. Traditional chrome plating the micro cracks in the plating extends thru to the substrate allowing for accelerated corrosion to occur.

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#10

Re: Stainless Steel Replacement

08/27/2009 2:31 AM

It is possible to hard chrome plate iron directly without a nickel (electroless or electro) plating step. Any pores will show rust marks if there is water around.

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#14

Re: Stainless Steel Replacement

08/27/2009 7:44 AM

Hi 1984,

Perhaps you want to look at replacing some of the stainless components with high grade AL ie. 6061 and anodize, depending on the size of the components this is likely chaeper, lighter, and will reduce the machining time of the component. Not knowing the design details of the project, we have no way of knowing if this is feasible in your case. Another option would be to redesign the machined components into die cast or stamped components, depending on your volumes of course.

Avoid Chrome plating of you can, the environmental concerns are real when using chrome plating and may put some high end customers off, unless there is a chrome plating process without haxavalent chrome.

MG

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#17
In reply to #14

Re: Stainless Steel Replacement

08/27/2009 3:29 PM

high grade AL ie. 6061

High grade? 2400 or 7500 series maybe

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#18
In reply to #17

Re: Stainless Steel Replacement

08/27/2009 4:02 PM

B Wire,

he is not likely building a stealth bomber for the nurses.

As we have no idea of the function, cost is next. 6061 is cost effective, and when anodized it may be strong enough.

Mirco.

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#19
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Re: Stainless Steel Replacement

08/27/2009 7:05 PM
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#15

Re: Stainless Steel Replacement

08/27/2009 9:51 AM

I am sure you probably checked before you posted but I am amazed at how low s/s prices have dropped to lately. Around 1-1/2 to 2 years ago I was buying a 21' piece of 8" Sch.. 10, 316 L S/S for $2500.00 and I think this is the highest I ever paid for this type pipe. Just a few weeks ago though I bought a piece of 6", Sch.. 10 316L S/S pipe and a piece of Sch. 6", 40 SA-106 B C/S pipe for a job I was doing in my shop. When I got my quote back I was really surprised to find the 316L pipe cost less than the C/S. In my 30 years of fooling with pipe I have never saw s/s prices this close to C/S prices. It has been my experience over the years that Sch. 10, 304 S/S is normally about 33% higher than Sch.. 40, SA 106 B C/S and Sch. 10, 316 is usually around 33% higher than 304. This is not wrote in stone but just a general rule I use to do + or - 25% cost estimates for pipe fabrication work. I haven't prices checked lately so it may have went back up some since I bought the pipe. I would definitely check it out before I replaced the S/S with C/S and went through the aggravation of the added steps to coat the C/S to prevent it from rusting. I think a lot of pipe and metal distributors mark up the prices they actually paid rather than go by the current market price on some items in order to stay in business. I also have found that checking with many different suppliers is a must when buying larger quantise of any type material. I sometimes send request for quotes to 6 or more different suppliers to be sure I get the best price possible on large orders.

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#16

Re: Stainless Steel Replacement

08/27/2009 11:55 AM

You'll need to check with the design of the parts. Why 303 and 440 is used. Is it for corrosion resistant only? What kind of strength is required of the part? Will the part be wash down? How about cleaning? Stainless require different cleaning then steel part to prevent rust to form on the part. Will the cleaner know its not stainless? It maybe in a room full of stainless equipment. Will stainless cleaner damage the plating? Plating tends to flick off. Will it cause heath concern?

303 is considered not magnetic. It is not a strong material. You almost can use any mild steel. Its not heat treatable.

440 is magnetic and can be heat treat to get higher strength. Was the design require magnetic or heat treatability?

Another concern is bacteria. Which material promote bacteria growth?

Now I maybe looking into it too deep but I've been making equipments for food and pharmaceutical plants. Sometime a new designer "forgot" the requirements. Better ask twice and make sure. Can't take any chances in these industries.

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#21

Re: Stainless Steel Replacement

08/28/2009 11:07 AM

I would suggest you look at the lower grades of Duplex S/S materials such as the 2101 LDX, It may well be that the cost of this material will be less than the 300 series stainless steels and still give the corrosion protection you need for your part. At one time the cost of the higher grades of duplex S/S was allot more reasonable compared to the cost of other S/S. Lately is seems that the cost of the higher grade duplex does not drop in the same proportions as 304 and 316 S/S. Because of these high costs I have used the 2101 LDX in certain applications instead of 2205 with good results. Just a thought that might be worth checking into.

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