Stainless Steel Replacement

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

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...

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.

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...

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.

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

TVP45, posting anonymously.

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.

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.

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

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.

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.

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.

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.

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

high grade AL ie. 6061

High grade? 2400 or 7500 series maybe

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.

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.

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.