cost saving grades 7

[mcguire]

If you exclude the 409 used for automobile exhaust systems, 304 is the most widely used type of stainless. It is a very appropriate grade for many applications, but for most, it is over-engineered.
In these days of expensive nickel, it is generally preferrable economically to use a stabilized 17%Cr ferritic when formability permits it. These grades have 30+% elongation compared to 304's 50+%. The cost savings in the elimantion of nickel is major, roughly 8% of $6 to $7 per pound, or $.50/lb.
If the forming attributes of 304 are required then a 5% nickel 201 can be substituted at a savings of $.20/lb. This alloy cannot be distinguished from 304 in forming or corrosion resistance if properly processed and if it has the correct level of manganese, carbon and nitrogen.
These alloys are usually only available on a mill direct basis. However, if you deal with a service center they can be obtained on a mill order basis if you place a long term contract with the service center.
I have helped many US companys save $millions by switching to 201 from 304. You don't need to buy heat lots, i.e. 100 tons, if you have fairly standard gauges and widths. You can possibly be a hero in your company by exploring this option.

 

[arunmrao]

"You can possibly be a hero in your company by exploring this option".

It is my observation that whenever such a change is made and a stoppage occurs, the plant and operations guys are immediately going to point their fingers at this change. The vendor will be blacklisted and the hero will be converted to a villain.


mcguire I support your proposal Many times 304 is just substituted by 200 series more popularly 202 grade. I have made a lot of substitution in this grade for paper processing industries. Also quite often 304L or 316 L is specified for parts in ESP used in cement plants. These are substituted by appropriate grades of heat resistant steels. This substitution has increased the life of parts and reduced downtime.

I can go on providing such examples in the pump and valves industry too. For this change to happen the end user and purchase department should be open minded.

A real problem affecting me now is the cost of Moly whch does not seem to be coming down. For the past 1 year I have stopped accepting orders for 316 grade of castings. Also low alloy steels containing moly continue to be a major headache.I have no ready solution for this and continue to produce these grades of castings at nil margins.

 

[mcguire]

Arunmrao
Lack of material is always a good way to become the goat. This can be solved by specifying both 201 and 304. Then the purchasing department has to answer for any shortage and explain why the more expensive alternative is used when he has to resort to 304.
With regard to substituting for molybdenum, this is harder. In flat rolled one can manipulate the chromium and nitrogen, enhance the surface finish, or minimize sulfur content to improve corrosion resistance. For instance a 304 with a bright annealed finish can equal a 316 which has been abrasively polished. Electropolishing gives even better results.
316L has a PREN of about 24. 304LN with 19% Cr and 0.14% N and a residual moly of 0.3% has a PREN of 24. There isn't much difference. Alloys can be engineered to achieve the desired properties if producer and the customer cooperate knowledgably. As you said in one of your previous posts, much money is wasted by rigidly following standard practices.

 

[arunmrao]

"As you said in one of your previous posts, much money is wasted by rigidly following standard practices."

Mcguire I sincerely hope that you have get enough opportunities to drive home this point to academicians, consultants,research bodies and all those who matter.

We shall conserve scarce resources and use them effectively too.

"Necessity is the mother of invention". Paucity of funds or materials is certainly going to be a driving factor. But this will be an extreme scenario I suppose.

Your book will be an eyeopener to this issue. Is Ed going to say something?

 

[EdStainless]

Maybe,
You knew that I couldn't reisist.
In service 202, 439 and similar alloys often work very well. Let's face it, most of time that SS is used is because you can't use CS, Cu or Al.
The rub in this is getting to the final product.
- The strain hardening rates on 202 are huge.
- I can't cold draw 439 (but I can draw 430).
And there are more examples. The 'simple' change in alloy may require a change in the entire manufacturing process.

My goal, day in and day out, is to get people to use the most effective alloy for their application. In many cases issues like availability and compatability with existing process are worth more than alloy cost and corrosion resistance.
And often, if you can get someone to discuss changing the alloy and process, they will come to the decision that a more expensive alloy would cost them less in the long run.

Do you want to cut costs? Look to use only the amount of metal that you need. In the tubing business I would guess that 80% of the applications use thicker walls than are needed. Start with the simple stuff.

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

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

 

[mcguire]

EdStainless makes good points. Getting customers to use the most cost effective alloy is the main daily battle.

I have to take some issue with the statement that 202 has a huge strain hardening rate. When I was at J&L we formulated 201 with 5%Ni, maximum alowable manganese,17% Cr, 0.05% C and 0.05% N. This gave a yield strength as low as 304 and the same strain hardening rate. The key is keeping the interstitials low. The cold rolling people couldn't believe it was 201 because it behaved just like 304. Our customers didn't have to change any tooling or forming parameters. It was used throughout the food equipment industry.

 

[EdStainless]

McG, Yes it can be done. The problem is getting the N low enough. No one wants to take the time (and Argon) to knock the N back to those levels. I can get 0.02% C all day, but anything lower than 0.07% N is dream.
Not to mention that I want some S to aid in weldability. You would think that 0.012% S was asking for the end of the world.

Let's face it, the mills are only putting effort into promoting alloys/grades that are proprietary. They would like to provide no tech support and no specials.
Not to mention bringing strip off of the DRAP line that is so underannealed that if you slit and rewind it, it will no longer meet the annealed properties.

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

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

 

[arunmrao]

http://www.azom.com/news.asp?newsID=2620

"Substitution in stainless sector affects Nickel demand". This was a banner I noticed in eng tips now and I have provided a link to the article .

Today I feel that Mo is a cause of greater concern as Ni prices seem to have plateaued.

 

[mcguire]

EdStainless
N can be blown down to 0.020% and it is done so fairly routinely in 409. They don't like it; you're right. Not only argon cost but AOD time. It affects their pay and you wouldn't want to get in the way of that.
Achieving precise sulfur levels is simple ladle metallurgy, but it, too, requires effort.

Arunmrao
Moly is a problem. Nickel can be easily eliminated, but moly is tough to replace. There are other ways to raise the pitting resistance, especially in castings, but people want a well-accepted solution. Maybe we should come up with a 316 equivalent without Mo. Alloy design 101.

 

[dgallup]

"In these days of expensive nickel, it is generally preferrable economically to use a stabilized 17%Cr ferritic when formability permits it. These grades have 30+% elongation compared to 304's 50+%. The cost savings in the elimantion of nickel is major, roughly 8% of $6 to $7 per pound, or $.50/lb."

So what would these low cost stabilized 17%CR ferritic grades be? We are currently turning bars of 304 (Carpenter project 70+) for fuel injector components. These parts have to be laser welded so any resulpherized grade like 303 is completely out. Machineablility must be equal or better than the 304. Beyond that the most important attribute is 96 hour 5% salt spray corrosion resistance which any 17% Cr SS should provide.

 

[mcguire]

dgallup
It's really encouraging to hear someone recognize the merits of the stabilized ferritics. They REALLY are the value grade in stainless. To get the same corrosion resistance as 304 it has to be titanium stabilized, but that is normal. In Europe they are commonly used instead of austenitics whenever formability permits.

 

[dgallup]

Mcguire

With the price of stainless steel today, we are definately looking for areas where we can make cost reductions. Do you have recommendations for specific grades?

 

[mcguire]

It's case by case. 304 is widely used because it is quite flexible in its use; for formability, for welding, for corrosion resisatnce. There can almost always be a less expensive substitute. It helps to be able to buy mill direct, which automotive suppliers usually have the volume to do. Give me specifics.

 

[EdStainless]

If you are looking at a ferritic with similar corrosion resistance to 304 then 439 would be the logical choice.
But, it is only available as thin sheet.
You can get 430 as bar stock, and then you have to worry about how it was heat treated.
Substitution isn't easy.

If your part is strength limited you should look at duplex grades. You can use so much less metal that it can save you money.

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

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

 

[arunmrao]

Ed forgive my ignorance if it is a stupid question. I am not familiar with preformed products. What limits a material from being available in all forms like rounds,squares,tubes, flats etc. Is it market dynamics or material characteristics. If it is the latter I have nothing to comment. But if it is a question of market dynamics then opinion makers like you should be able to see that a particular grade of material is available in economic quantities in all forms . Is it asking for too much?

 

[mcguire]

Certain types of stainless steels, notably the stabilized ferritics, do not undergo any grain-refining phase changes below their solidification temperature. Since the deformation of bcc ferrite is temperature activated, they are brittle below temperatures near room temperature. This transition temperature is largely a function of grain size.
It is hard to produce flat rolled 439 with a fine grain size above about 1.5 mm thickness because it's difficult to put enough cold work into it to drive the recrystallaization nucleation required for a fine grain size. Therefore anything above 1 to 1.5 mm tends to be quite lacking in toughness.

 

[EdStainless]

Good job McG.
The other issue with the ferritics is being able to quench them hard enough to keep them fully ferritic. In the higher alloy grades there are a lot of various intermetallics that want to form. Since the quech rate is thermal conductivity limited your product forms become thickness limited. We will not run over 0.109" wall thickness.
The ductility and DBT on 439 (and 409) get worse as the material gets thicker, even when the grain size is constant. If you toss in larger grains too you have trouble.

You can keep 430 fine grained because you get a little bit of martensite. When you temper and then anneal you get rid of it, but you also get recrystallization. We have run 430 in wall thicknesses of 0.165".

One big problem with the forming of ferritics is that they do not strain harden much. This limmits the degree of cold work per pass to a lower level than is common in austenitic grades.

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

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

 

[rolledalloy]

The LDX 2101 duplex stainless follows the same idea as the 201 does. Reduce the nickel by substituting manganese. It is duplex in contrast to 2205 (5% nickel) it has only 1% nickel. It also has only 0.3% Moly so it is much less impacted by the surcharges than 2205 (3% Mo) or 316L (2% Mo). With 21%Cr, 0.3%Mo, and its nitrogen addition it still has a pitting resistance equivalent number and critical crevice corrosion temperature similar to 316L.

 

[unclesyd]

From the Chemical Plant standpoint I'm a little worried about the recommended substitution of different stainless steel based on properties that carry little relevance in a facility that uses or produces reactive (corrosive)products.

Our materials of construction are all based on extensive laboratory immersion corrosion, heat flux, inline exposures, and so on. Each material choice was made by metallurgists and material engineers after extensive material evaluation. As stated before we had an extensive and complete metallurgical laboratory complete with a joint electrochemical research group.

Our process was essentially a very large chemical test bed that required constant monitoring and continual evaluation of MOC's.

We had processes were the material of choice was 304L with limits on certain elements. Using the buzz word, We were proactive in evaluation of different materials for this process and got burnt by several better, high purity, materials. This particular process requires actual field test as laboratory tests normally result in explosions. This process is exothermic and you can imagine the problems with cooling using 304L SS exchangers, we would like something different. We have stared a move to titanium as the price has dropped to point where it getting to be viable option.
As I’ve stated before the product produced in this area is benign until it gets to its melting point then the corrosion rate for 304L goes asyemtopic and 316 is used, then Titanium , then Hastalloy C, then Cu.

I’ve mentioned before our famous, expensive, experiment with Hastalloy C tubing in a vertical condenser that was condensing a product that had small amounts of Formic and an Organic Peroxide in the stream. Literature suggested that Hastalloy C would be a good candidate. A lab immersion test gave the Ok for an in service test tube. After a lengthy inservice test it was decided to go with two exchangers at a little over $1,000,000 for the pair. The first one was installed and with several weeks it was noted that we had leaking tubes. Inspection revealed a complete failure of all tubes. The tubes were all dissolving to a depth equal to tubesheet thickness. Below the tubesheet the tubes were pristine. This bundle was salvage using rolled in sleeves. The second bundle was sleeved prior to installation. An slight increase in the Formic and Peroxide killed the condensers. The use of this particular sleeve was the first time I ever used a material without testing, it was the only thing available.

We have columns with the bottom 316 SS and top 304L and vice versa all based on testing. We used Silicon Bronze and Cu at over 600°F all based on testing.

Though the above is a little wordy material changes in a chemical enviroment require a little more than price or as good as or better than. Even with complete testing and evaluation you still can get burnt bad. We tried to select the material and let the vessel designers go from there.

I know times are changing, but being natured in this type enviroment I am still awful cautious on material changes.

 

[mcguire]

Thank you for the valuable sharing of an expensive lesson. You deal with very specialized environments and expensive installations. Caution must be the guiding principle. Your outfit does it right.
I would still maintain that for the vast majority of stainless use, which is in atmospheric and aqueous ambient environments, experiments with substitution should be encouraged. If 439 and 201 were used in the the applications for which they are suitable, the price of nickel would come down dramatically.
Lean duplex with low moly could do the same to moly cost.
We engineers waste scarce commodities in our nickel and moly usage.