Cast iron or steel

[openspaceman]

But isn't high grade steel stronger than cast iron? Obviously the cheaper Chinese made stoves are to be ignored.

 

Strength isn't an issue in a stove, corrosion is. Steel will resist oxidation at fairly high temperatures but get it too hot and it burns at the grain boundaries. As cast iron has a much higher carbon content these grain boundaries are occupied by carbides and graphite, which though it is pure carbon is highly resistant to oxidation. You can see this if you first oxyacetylene cut a sheet of mild steel and then try the same with a similar piece of cast iron.

 

I don't know which steel alloys might offer the same corrosion resistance as cast iron but my guess is a steel stove with refractory brick liners will last well and as the combustion temperatures will be higher should be cleaner burning too.

[agg221]

This is a simplification, but in essence a lot of the confusion over materials arises because 'iron' and 'steel' are not simple things.

 

Iron is an element. It has quite a high melting point, doesn't corrode quickly but is relatively soft and has very little high temperature strength. Other elements are therefore added to iron to change its properties.

 

The smelting process (making pig iron from ore) results in a composition with a lot of carbon and silica (melted sand) in it. The carbon alloys with the iron, lowering the melting point and making it brittle (but actually improving the high temperature stiffness). To make it useful, it needs to have some of the impurities removed.

 

Pre-industrial revolution, the only options were to heat the iron and hammer out the impurities, eventually making wrought iron, or to 'burn' some of them out, making cast iron which still contained a fairly large amount of carbon and hence was still rather brittle, although with excellent high temperature stiffness. Throughout the Victorian era, these were pretty much the only options for large volume material. The development of processes for volume steelmaking e.g. the Bessemer process) changed this in the 20th century.

 

Steel is an alloy of iron with controlled quantities of other elements, often including carbon at up to ~2%. These elements, such as manganese, nickel or chromium, are selected to improve hardness (e.g. cutting tools), high temperature stiffness, corrosion resistance to heat, seawater, acids etc. Because there are so many possible applications, there are also loads of different steels, optimised to meet them. There are steels designed for continuous service under high pressure at over 750degC without corroding or deforming, which would have your whole stove glowing cherry red! The steelmaking process has become so universal (and so much cheaper) that it has effectively completely replaced wrought iron, through the supply of 'mild steel' which is basically iron with a very small amount of residual carbon.

 

So, if a stove is made of 'cast iron' you know it will be stiff and hold up well at high temperatures, even if the material is relatively cheap. However if it's too cheap then it may not have been refined enough and hence crack easily. If it's made of 'steel' there is a huge variety available, which at the high end could mean it's much better than cast iron and at the low end means it's much worse. This is where you have to trust the manufacturer.

 

Not sure if this helps or not!

 

Alec

[cornish wood burner]

But isn't high grade steel stronger than cast iron? Obviously the cheaper Chinese made stoves are to be ignored.

 

Yes high grade steel is tougher, stronger and will stand shock loads better.However at high temperatures found in a stove cast iron expands less, corrodes less and as TGB said is more stable and should not distort.

[Scotty38]

Just bought a Clearview Pioneer which is steel. I'm hoping it's going to be ok and last me a good few years

[richardwale]

It's all down to efficiency, surely. Pay half decent money for a stove, steel or cast, I'd want to use less fuel for maximum heat.

[waterbuoy]

I've had seven different stoves in my last three houses. Most of themwere cast iron (usually from Vermont Castings) - the stoves were OK but innards tended to distort after a while. The steel ones tend to deform least (all Clearview) when using the same fuel etc.

 

Just to throw a spanner in the works, my favourite was actually a Dutch stove which had a cast iron outer frame but in which the main panels were actually made of soapstone, about 20-25mm think. Whilst it may have taken a good while to warm up it gave out a very steady and uniform heat,often running for more than 24 hours between fills. Sadly I cannot remember the manufacturer.

[TimberCutterDartmoor]

No matter what anyone says, cast iron or more latterly compacted graphite iron will always the superior material from which to build engine blocks, crankcases etc. Less expansion, better thermal characteristics, better lifespan. Not light weight no hence the lions share of i/c engines are now alloy / allu with liners.

 

Funnily enough, kioritz engines in Echo chainsaws have a higher iron content than any other 2-cycle.

 

Sorry for the slight derail.

[Alycidon]

Alycidon?

 

Here< bloody busy selling stoves so only just got here today.

 

Right then cast and steel plate stoves.

 

Given the same quality level a cast iron stove will take longer to get hot but hold the heat longer when the fire goes out.

 

Cast iron today is about 80% reclaimed, its melted down then re cast. Once it comes out of the mold it is inspected for any blemishes, some manufacturers have an x ray facility to check castings internally. If a blemish is found then the whole thing has to be re cast, spotting a blemish is easy if you have a finely finished casting such as that on a Morso but others with rougher surface finishes may hide blemishes. The other issue is air bubbles and lack of key additives within cheap castings, usually of Chinese or Soviet origin, the air in these expands and contracts over the stoves usage cycle and eventually the casting cracks. AT that point is usually new stove time.

 

Plate steel stoves providing they are made from thick plate are fine, most good quality manufactures use 6mm - 8mm thick plate, the thicker plate in the higher stress areas. Steel stove bodies are usually built my machine so are more accurately made and are cheaper to produce. Good quality manufacturers then in a traditional sized stove add a cast iron door, that is a market led thing.

 

I have seen Chinese steel stoves with 3mm steel plate, as soon as that gets hot it will buckle. Utter rubbish.

 

The cast iron stove is now about as far developed as it can get with the Morso Badger, production costs for cast are far higher than using steel so almost all manufacturers bringing a new stove to market will launch steel body with cast door but some contempory stoves such as the Esse 125 are totally steel.

 

Stick to a good brand and a steel stove should have the same service life as a cast iron one. The Arada group ( Aarrow and Villager) now offer a lifetime casing warranty, their stoves are all steel body with cast doors.

 

Hope that helps.

 

A

Edited October 31, 2015 by Alycidon

[mendiplogs]

Here< bloody busy selling stoves so only just got here today.

 

Right then cast and steel plate stoves.

 

Given the same quality level a cast iron stove will take longer to get hot but hold the heat longer when the fire goes out.

 

Cast iron today is about 80% reclaimed, its melted down then re cast. Once it comes out of the mold it is inspected for any blemishes, some manufacturers have an x ray facility to check castings internally. If a blemish is found then the whole thing has to be re cast, spotting a blemish is easy if you have a finely finished casting such as that on a Morso but others with rougher surface finishes may hide blemishes. The other issue is air bubbles and lack of key additives within cheap castings, usually of Chinese or Soviet origin, the air in these expands and contracts over the stoves usage cycle and eventually the casting cracks. AT that point is usually new stove time.

 

Plate steel stoves providing they are made from thick plate are fine, most good quality manufactures use 6mm - 8mm thick plate, the thicker plate in the higher stress areas. Steel stove bodies are usually built my machine so are more accurately made and are cheaper to produce. Good quality manufacturers then in a traditional sized stove add a cast iron door, that is a market led thing.

 

I have seen Chinese steel stoves with 3mm steel plate, as soon as that gets hot it will buckle. Utter rubbish.

 

The cast iron stove is now about as far developed as it can get with the Morso Badger, production costs for cast are far higher than using steel so almost all manufacturers bringing a new stove to market will launch steel body with cast door but some contempory stoves such as the Esse 125 are totally steel.

 

Stick to a good brand and a steel stove should have the same service life as a cast iron one. The Arada group ( Aarrow and Villager) now offer a lifetime casing warranty, their stoves are all steel body with cast doors.

 

Hope that helps.

 

A

 

HI GEOFF as you say CAST IRON HOLDS heat very well after fire gone out thanks Jon

[agrimog]

the stove in my house is a beautifull old cast iron one, gets very hot and keeps the heat for hours, never causes any problems, other than a bit of having to black lead it to keep it looking good, the one in the workshop is made entirely from steel, it varies from 15mm to 25mm thick, it takes foreever to warm up when its first lit, (usually around now), but it will radiate a reasonable heat for days on very little wood, mostly being fuelled by offcuts from the workshop, it was consructed from offcuts of boilerplate from a well known steel supplier and a lot of stick rods, and it will definatley see me out, so whether iron or steel, doesnt matter as long as its made from quality stuff