case hardening mild steel

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case hardening mild steel

This topic has 47 replies, 8 voices, and was last updated 16 January 2012 at 20:08 by kristian woolf.

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5 December 2011 at 18:12 #79267
kristian woolf
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@kristianwoolf80751
Hi ,

I am in the design process of creating a model steam engine for my engineering project at school, and Im not sure what materials i should use for the cyclinder. Would it be any good to machine the mild steel then do the case hardening process or would that warp the dimensions. Or should i use different materials for the cylinder and piston. Thankyou
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5 December 2011 at 18:12 #29450
kristian woolf
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@kristianwoolf80751
5 December 2011 at 18:47 #79269
michael howarth 1
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@michaelhowarth1
Kristian…..mild steel does not sound like a very good idea to me. (Corrosion) Cast iron is often specified for loco. cylinders but can be problematic. For small steam engines, gunmetal is usually the preferred option for the cylinder with either a phosphor bronze or brass piston. If you intend to fit the piston with ‘O’ rings then the cylinder and piston can be made of brass…… this is the cheapest way to do it. Obviously I do not know what sort of steam engine you have in mind, but I have seen plans for simple models where thick walled brass tubing is used for the cylinder with ‘O’ ring fitted pistons. There are a good few sites on the net which have plans for steam engines.

Edited By mick H on 05/12/2011 18:48:11
5 December 2011 at 19:16 #79270
kristian woolf
Participant
@kristianwoolf80751
Thankyou for your reply , The engine is a stationary engine and the cyclinder will be a 12mm hole reemed into a block of metal. It is quite hard to explain how I have done it but my engineering teacher reckons it should work if i get the timing right in the valves. Do you know where I can get hold of gun metal. Thankyou
5 December 2011 at 19:18 #79271
Jeff Dayman
Participant
@jeffdayman43397
Hi Kristian,

A plain unhardened mild steel cylinder will last a very long time in a model, if you include a displacement lubricator in the steam line for oiling the inside and you paint the outside to keep rust down. A brass or phosphor bronze piston will work great in a mild steel bore (or a cast iron bore). Don’t bother case hardening a mild steel cylinder, there’s really no need, unless you plan to run the model every day for ten years.

A cast iron cylinder will also work very well, especially if you can get a small piece of ‘meehanite’ grade cast iron stick, it will turn and mill beautifully and run a very long time, as long if not longer than mild steel. Most full size steam engines had cast iron cylinders so it’s likely not an accident !

Brass will work as a cylinder too, but its’ life depends on what kind of brass it is. Soft brass may wear kind of quickly. Bronze is great too, but usually a bit expensive.

If you need plans for a displacement lubricator try one of the “simple steam” books by Tubal Cain. All kinds of good advice in there.

By the way, stay away from aluminum for any parts that are exposed to steam (or that need inertia, like flywheels). Some grades of aluminum corrode and wear rapidly in steam depending on the grade.

Good luck with your project.

JD

Edited By Jeff Dayman on 05/12/2011 19:19:36
5 December 2011 at 19:28 #79272
kristian woolf
Participant
@kristianwoolf80751
Thankyou again,

Thankyou for this post just looked at some prices of gunmetal !!!!!! I was going to but a hole or something in above the piston so that it can be oiled but I needed to find an effective way of doing so. Thanks I will take a look at that book.
5 December 2011 at 19:30 #79273
kristian woolf
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@kristianwoolf80751
Also luckily at school we have a huge chunk of bronze, about a kilo that we are allowed to use, but know ones found a use for it yet.
5 December 2011 at 19:48 #79274
michael howarth 1
Participant
@michaelhowarth1
Kristian…..Jeff has given you something else to think about in his post, above. I think it is fair to say though, that whilst in theory properly lubricated steel and cast iron cylinders might not suffer from corrosion, correspondence in Model Engineer over the years tends to indicate that there are frequently inadequacies in that direction which can have catastrophic consequences especially if the engine is used infrequently and moisture is inevitably left in the cylinder.

I have no connection whatsoever with the company but if you click on “suppliers” at the top of this page, Macc Models is listed and they stock gunmetal.
5 December 2011 at 20:02 #79275
michael howarth 1
Participant
@michaelhowarth1
Kristian……I have only just seen your last two posts…..we were obviously both submitting together but you got in first……yes gunmetal is quite expensive and if you can cut out the bit that you need from the bronze that will be ideal. I think that you will need something more effective as a lubricator than a simple hole in the cylinder. The books by Tubal Cain that Jeff mentioned are good…..I loaned mine to someone who didn’t return it……I do however have another small book on building a simple stationary steam engine that you are welcome to if and when I can lay my hands on it. I think it must be in my shed but I am not going out there tonight!!! I will PM you when I find it.
5 December 2011 at 20:15 #79277
kristian woolf
Participant
@kristianwoolf80751
Thankyou if you could do that id be really grateful and get some money off to you. The price of this gun metal is considerably cheaper than what I saw earlier thankyou. About £150 cheaper!!
5 December 2011 at 20:53 #79279
Terryd
Participant
@terryd72465
Hi Kristian,

For a school project you can get away with a mild steel (unhardened) cylinder and brass piston. As long as the materials are different the problem of wear is not important. Especially as you will only run this engine for a short time – probably.

You can lubricate the engine automatically with what is called a ‘displacement lubricator’, This is a very simple device which is fitted into the steam line before it enters the cylinder, as the steam passes through, a bit of it condenses into the oil reservoir as water and a drop of oil is ‘displaced’ into the steam line and lubricates the cylinder. They are very simple to make. Here is an explanation of how they work (and a bit more about steam engines), just scroll down the page a bit.

I wish you ever success with your project. Just enjoy making this one and you can worry about fine detail with your next one. If you get really interested there are lots of books on simple steam engines which you can get from your local library.

Good Luck,

Terry

Edited By Terryd on 05/12/2011 20:54:20
6 December 2011 at 04:46 #79288
Terryd
Participant
@terryd72465
Hi Again Kristian,

I forgot that there are some ideas for displacement lubricators here and here. The first one gives an exploded view to show how they work and the second has a detailed plan to make one.

Regards

Terry

Edited By Terryd on 06/12/2011 04:48:21
6 December 2011 at 09:33 #79300
michael howarth 1
Participant
@michaelhowarth1
Kristian…I have left you a PM re the book
6 December 2011 at 10:28 #79304
Ian S C
Participant
@iansc
Kristian, I, made 4 or 5 little oscillater motors, ranging from a 6 mx 12 mm V twin, to a 3mm x 6 mm single, that last motor actually powered a boat. I used brass cylinders, and stainless steel pistons. The V twin has a displacement oiler similar to the ones discribed by Terry.

Mild steel would be OK if you were going to run the motor on air, although it helps if the compressor has a water trap. Ian S C
6 December 2011 at 18:34 #79331
kristian woolf
Participant
@kristianwoolf80751
Does anyone know where I can get some brass or something similar for the cylinder of about 45×40 square and 70 mm long. 3 Pieces. Iv looked all over ebay and there is absolutely nothing I can find.
6 December 2011 at 21:44 #79356
Terryd
Participant
@terryd72465
Posted by kristian woolf on 06/12/2011 18:34:17:
Does anyone know where I can get some brass or something similar for the cylinder of about 45×40 square and 70 mm long. 3 Pieces. Iv looked all over ebay and there is absolutely nothing I can find.

Hi Kristian ,

Look here – 2″ square is the nearest bar size – and be prepared for a surprise, copper and it’s alloys such as brass is very expensive at the moment (hence all the thefts of railway signalling cables etc) and looking at several model engineering materials suppliers for the size you require it would cost around £8 to £9 per 25mm length i.e approx £70.00 to £80.00 (plus around £10.00 delivery) for what you apparently need from a small quantity supplier.

That is why I suggested that you use mild steel for your cylinders for a school project. Don’t be too ambitious, that way leads to disappointment and frustration, simple and easy is the way to go at first, believe me,

By the way, 40 x 45 mm is not square, it is rectangular bar.

Best regards and good luck,

Terry

Edited By Terryd on 06/12/2011 21:59:40
6 December 2011 at 21:53 #79357
kristian woolf
Participant
@kristianwoolf80751
Okay thankyou, it does look very expensive, Ill see what school has in its stock and Illl see what I can do
7 December 2011 at 09:07 #79381
michael howarth 1
Participant
@michaelhowarth1
Kristian….that is a massive cylinder block for a 12mm bore cylinder. What about heat loss as well?

Mick
7 December 2011 at 13:36 #79391
Ian S C
Participant
@iansc
For a simple steam engine, brass tube is normally good enough for a cylinder, for small engines at least. I’v found that soft solder is quite OK for attaching a block on the side of a bit of brass tube to create the valve area, and pivot point for the oscillating cylinder. Ian S C
7 December 2011 at 14:24 #79395
Richard Parsons
Participant
@richardparsons61721
Kristian Do not worry about rust if you use an oiler in your steam supply. . A quick squirt of WD40 into the exhaust with the exhaust open will fix it. Do not case harden your piston or cylinder. Hardened steel is far more susceptible to rusting than unhardened steel.

Running steel in oiled cast iron bearings is a far more common thing than you think. I worked in a factory where we had some 200 Singer industrial machines. They ran 10 hours per day. Though some were over 30 years old we seldom had breakdowns due to worn bearings. My little Lorch lathe which is about 100 years old still has dead smooth but rock solid headstock bearings.

Good luck an enjoy the work

Dick
7 December 2011 at 14:44 #79397
michael howarth 1
Participant
@michaelhowarth1
Richard and Terry…….I wonder whether I am missing something fundamental…a while back there was a thread concerning condensation and subsequent rust etc forming on tools and machines and this despite treatments with various oils, waxes and assorted unguents. You have both mentioned the use of mild steel as suitable material for a steam cylinder and this seems to be contrary to what I and others have experienced when steel and water get it together…..oil or no oil.

I am about to embark on an outside cylinder loco shortly…….should I abandon thoughts of gunmetal castings for the cylinders and fabricate them out of mild steel? Definitely cheaper.
7 December 2011 at 15:53 #79406
Jeff Dayman
Participant
@jeffdayman43397
Hi Mick,

For a locomotive my first choice for cylinders would be cast iron with a bronze or brass piston and stainless piston rod. If kept well oiled and used often there will not be a rust problem. Over long use the iron will develop a deep polished black finish that will work well with most piston seals and will run beautifully with little friction.

If loco is to be stored for a long time, a preservative heavy oil spray known as “fogging oil” can be used to prevent rust, these have been used for many years on small IC marine engines and snowmobiles off season here in North America. It is sprayed in through the air inlets of running IC engines until the engine stalls, indicating the cylinders and spark plugs are well wetted. It can also be sprayed into open spark plug holes (or steam engine exhaust pipes)

My second choice for loco cyls is gunmetal/bronze, it won’t rust, it will work well, but it is too expensive for me, hence second choice.

Just my $0.02 your mileage may vary

JD
7 December 2011 at 16:55 #79408
Terryd
Participant
@terryd72465
Posted by mick H on 07/12/2011 14:44:25:

Richard and Terry…….I wonder whether I am missing something fundamental…a while back there was a thread concerning condensation and subsequent rust etc forming on tools and machines and this despite treatments with various oils, waxes and assorted unguents. You have both mentioned the use of mild steel as suitable material for a steam cylinder and this seems to be contrary to what I and others have experienced when steel and water get it together…..oil or no oil.

I am about to embark on an outside cylinder loco shortly…….should I abandon thoughts of gunmetal castings for the cylinders and fabricate them out of mild steel? Definitely cheaper.

Hi Mick,

Mild steel is ok if there is a steam oil supply perhaps through a displacement oiler and a drain cock of some kind. It will last ok if run on compressed air. Remember cylinders on real locos weren’t made of bronze, brass or gunmetal, they were cast iron. When water and cast iron get together the result is also rust.

Remember the project we are talking about is by a young student probably with limited resources and experience, for a gcse. One of 10 or 12 he will be taking. The engine may not run on steam given the time available in the school workshops it is unlikely that a decent boiler could be made anyway. A lot of us run our stationary engines on compressed air these days. Knowing students as I do there will probably be many errors and mistakes along the way, your way could be very expensive for a 15 year old.

In these circumstances it is not always the ultimate solution but the realistic one which must be considered. There has to be compromises. If he finds that he likes the hobby he has a lifetime ahead to go for the ultimate.

In your case I would think that mild steel would be ok if you were to merely run it for a few hours for fun or as a demonstration and then put it on display. However if you wish to run the loco regularly under steam I suggest that your first solution i.e. gunmetal is he choice you should and will go with.

It’s simply horses for courses.

Regards

Terry
7 December 2011 at 17:13 #79411
kristian woolf
Participant
@kristianwoolf80751
Posted by Terryd on 07/12/2011 16:55:34:

Posted by mick H on 07/12/2011 14:44:25:

Richard and Terry…….I wonder whether I am missing something fundamental…a while back there was a thread concerning condensation and subsequent rust etc forming on tools and machines and this despite treatments with various oils, waxes and assorted unguents. You have both mentioned the use of mild steel as suitable material for a steam cylinder and this seems to be contrary to what I and others have experienced when steel and water get it together…..oil or no oil.

I am about to embark on an outside cylinder loco shortly…….should I abandon thoughts of gunmetal castings for the cylinders and fabricate them out of mild steel? Definitely cheaper.

Hi Mick,

Mild steel is ok if there is a steam oil supply perhaps through a displacement oiler and a drain cock of some kind. It will last ok if run on compressed air. Remember cylinders on real locos weren’t made of bronze, brass or gunmetal, they were cast iron. When water and cast iron get together the result is also rust.

Remember the project we are talking about is by a young student probably with limited resources and experience, for a gcse. One of 10 or 12 he will be taking. The engine may not run on steam given the time available in the school workshops it is unlikely that a decent boiler could be made anyway. A lot of us run our stationary engines on compressed air these days. Knowing students as I do there will probably be many errors and mistakes along the way, your way could be very expensive for a 15 year old.

In these circumstances it is not always the ultimate solution but the realistic one which must be considered. There has to be compromises. If he finds that he likes the hobby he has a lifetime ahead to go for the ultimate.

In your case I would think that mild steel would be ok if you were to merely run it for a few hours for fun or as a demonstration and then put it on display. However if you wish to run the loco regularly under steam I suggest that your first solution i.e. gunmetal is he choice you should and will go with.

It’s simply horses for courses.

Regards

Terry

Its for my A level project so we have pretty much unlimited time and our engineering workshop is pretty good for a schools. We have just had a new ALC block built with around £1 million worth of equipment.

I have managed to get hold of some large round 6 inches ish cast iron bar which i will use for the cyclinder now.
7 December 2011 at 18:59 #79417
michael howarth 1
Participant
@michaelhowarth1
Thanks for the reply Terry…..I happily defer to your experience with students and I now see the direction that you are coming from. I must say that I was looking at it more from the investment of time in the project…..which at my end of the scale is more valuable than the price of a lump of gunmetal ! I see from the post above that Kristian has managed to lay his hands on a 6 inch lump of cast iron……..now that would cost a few shillings in gunmetal.

Thanks also Jeff for your reply…….I fully understand the use of cast iron in full scale practice but I am also aware of considerable correspondence in the past in ME where corrosion in CI cylinders has wrecked them……..I think that this was probably due to the somewhat unreliable lubrication methods used in small models …….also the subject of much correspondence. That fogging spray sounds like good stuff.

Mick
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