Bad Steel in the Rolls-Royce Merlin?

[SKR_01]

Hi people!
I had a dispute with a friend: he claims that Merlin had poor-quality steel. I know that RR used the mark steel KE.965 for valves, but I do not know how this circumstance is with this industry.
If there are people here who are familiar with Merlin or how good is British steel in the 30s and 40s?
Sorry for my English.

 

[bobbysocks]

seemed to be a pretty reliable engine for supposedly having been made of poor steel... I have never read of pilots not trusting the engine or massive accounts to blowing the engine because they ran it too hard.

 

[fubar57]

Western engine reliability

 

[pbehn]

Hi people!
I had a dispute with a friend: he claims that Merlin had poor-quality steel. I know that RR used the mark steel KE.965 for valves, but I do not know how this circumstance is with this industry.
If there are people here who are familiar with Merlin or how good is British steel in the 30s and 40s?
Sorry for my English.

As a retired metallurgist (of sorts) the term "bad steel" is not applicable. There are dozens of different metals in an engine and not all are steels. There are discussions you can read here about the Allison being more reliable than the Merlin but that is by degrees, the Merlin was extensively tested and used on British (UK) and US aircraft from the start to the end of the war.

In a theoretical case, if a big end seizes due to poor lubrication then the con rod may snap, that is not a sign of bad steel but poor design or servicing.

 

[SKR_01]

Tell me, what methods of steel production were in the 30's and 40's in Britain?

 

[pbehn]

Tell me, what methods of steel production were in the 30's and 40's in Britain?

The subject is tied up in language that confuses most. Steel is an alloy of Iron and Carbon. However when you produce Iron using coke for heat it has a high carbon content. Refining steel from this "Iron" from a blast furnace involves reducing the amount of carbon not increasing it. Most Steel in UK at the time was refined using the Bessemer process or open hearth process, the Basic Oxygen steel process was developed in the post war period,


Blast furnace - Wikipedia
Bessemer process - Wikipedia
Open hearth furnace - Wikipedia
Basic oxygen steelmaking - Wikipedia


However the process is a small part of the story, the real problems are in testing. I started work in 1977 and was trained in chemical analysis by wet methods. It took two people a whole day to test forty samples for all elements, now it takes a few seconds per sample. In heat treatment I met old guys who could tell the temperature of molten and solid steel with their eyes. In heat treatment temperature is vitally important but how could you measure it to nine hundred and ten plus minus five celcius in 1940? Similarly, ultrasonics didn't exist and radiography was primitive, how do you test for internal defects? The problems were not really in production but in quality control and quality assurance.

At the time the biggest metallurgical problems were in jet engines, The UK at the time was the equal of the USA in this field. Germany had different problems because they couldn't get expensive and rare alloy elements but came up with passable solutions despite this.

 

[pbehn]

seemed to be a pretty reliable engine for supposedly having been made of poor steel... I have never read of pilots not trusting the engine or massive accounts to blowing the engine because they ran it too hard.

If you did this would more likely be a problem of oil feed, oil type or bearing quality. Various "dodges" like tuftriding and ball peening increased the service life of engine parts but this is not really a question of "bad steel". Some manufacturers have had problems in the past with things like valves and rings for example, this is usually poor heat treatment not the steel itself.

In my youth Honda had a problem with their 900cc engines breaking con rods when used for racing. The solution was to use a smaller not bigger "big end" housing. The smaller connecting rod being lighter put less load on the crank and bearings. Any layman would blame the steel used in the engine when in fact the problem was the engine design itself.

 

[pbehn]

Hi people!
I had a dispute with a friend: he claims that Merlin had poor-quality steel. I know that RR used the mark steel KE.965 for valves, but I do not know how this circumstance is with this industry.

KE 965 was developed by Kayser Ellison and co in 1937

C= 0.4 Cr =13 Ni =13 Si -1.5
UTS = 156,000PSI, elongation 27% reduction in area 49% Brinell hardness 265. Heat treated
Non distorting for valves and supercharger buckets.

"Developed to replace EN52 as an exhaust grade steel, this steel possesses excellent creep strength and impact values at high temperature, and has good scaling and corrosion resistance, except in the presence of sulphur, and its resistance to oxidation extends to temperatures above 900 Deg. C. "

"Creep" is the elongation of materials at high temperatures under low load over a long period of time..

 

[yulzari]

In my youth Honda had a problem with their 900cc engines breaking con rods when used for racing. The solution was to use a smaller not bigger "big end" housing. The smaller connecting rod being lighter put less load on the crank and bearings. Any layman would blame the steel used in the engine when in fact the problem was the engine design itself.

Very good Pbehn. We found the same thing with Chevrolet V8s in Formula 5000 engines. The smaller diameter cranks pins had a slower speed over the bearing surface and the oil could cope better. The steel was of little significance.

 

[pbehn]

Very good Pbehn. We found the same thing with Chevrolet V8s in Formula 5000 engines. The smaller diameter cranks pins had a slower speed over the bearing surface and the oil could cope better. The steel was of little significance.

I used to read quite a lot on stuff like tuning the Ducatis for Hike Hailwoods comeback. Many of the solutions were like the one you describe, counter to what appears logical to the lay man. That is because I am a lay man and not an engineer. The Rolls Royce Merlin was one of the oldest designs of front line WW2 in line water cooled engines, it also had one of the smallest swept volumes. Despite this the last versions were over 2000 BHP. If it had any serious reliability issues it would not have been the engine in the P51, you cannot send hundreds of single engine fighters on six hour missions over enemy territory with dodgy engines.

 

[fastmongrel]

Possibly things have got confused between the RR Merlin aero engine and the Meteor tank engine which was mostly developed by Rover. The Meteor had around about 75% parts common with the Merlin and used some parts that had not managed to pass tests for air use. A broken valve spring over Germany can mean a bail out, a broken valve spring in a tank means burning oil till you can get out of the combat zone and then a few hours fitting a new engine. Meteors also used parts from RR and Packard Merlin engines that had exceeded the hours allowed for air use or had gone out of tolerance.

RR used the "rev it till something breaks and then work out why it broke and how it can be strengthened" testing method. The residents of Derby must have spent many hours with their fingers in their ears as the latest V12 was run to destruction in the test bays.

Many RR developed Ferrous and Non Ferrous alloys were used for many years as industry standards in the UK so I doubt that RR who could have had any materials they wanted from the UK and US would have used inferior steels.

 

[pbehn]

Possibly things have got confused between the RR Merlin aero engine and the Meteor tank engine which was mostly developed by Rover. .

The original post was from a guy in Russia, the Merlin may have a different reputation there, but that may be due to operating conditions or different fuels and lubricants.

 

[swampyankee]

Various "dodges" like tuftriding and ball peening increased the service life of engine parts but this is not really a question of "bad steel".

Shot peening and ball [hammer] peening are very useful processes for improving fatigue resistance, as they induce compressive residual stresses near the surface; I'd not call them dodges, even in scare quotes

I suspect that a thorough and accurate multi-national comparison of steel (and other alloy) quality from the WW2 era and before is impossible, for several reasons, first of which is that "quality" in this context doesn't mean "better," but consistent, so one would need at least dozens of test reports for each alloy, each vendor, and each type of process hot rolled, cold rolled, cast, stamped, different heat treatments, .... and that the ways these data are reported differ between countries, e.g., Germany and the US used different methods of reporting elongation.

 

[pbehn]

Shot peening and ball [hammer] peening are very useful processes for improving fatigue resistance, as they induce compressive residual stresses near the surface; I'd not call them dodges, even in scare quotes

I suspect that a thorough and accurate multi-national comparison of steel (and other alloy) quality from the WW2 era and before is impossible, for several reasons, first of which is that "quality" in this context doesn't mean "better," but consistent, so one would need at least dozens of test reports for each alloy, each vendor, and each type of process hot rolled, cold rolled, cast, stamped, different heat treatments, .... and that the ways these data are reported differ between countries, e.g., Germany and the US used different methods of reporting elongation.

I agree Swampyankee,it is always difficult to choose the language. What I meant by a "dodge" was a method to increase the serviceability of a component without changing the other basic production process. In the Merlin the pistons are Aluminium alloy, the big end beaings are lead bronze, the little ends are phosphor bronze, the con rods are nickel steel forgings, the crankshaft is a Ni Cr Mo steel hardened with nitrogen while the crank cases are Aluminium. The critical parts are either not steel at all or completely out with what people regard as "steel". I have worked with stainless "steels" where Iron is quoted as "balance" and Carbon is less than 0.03% even though steel is supposed to be an Iron Carbon alloy. They are actually Cr Ni Mo Fe alloys but "steel" is a convenient collective word.

 

[swampyankee]

I agree Swampyankee,it is always difficult to choose the language. What I meant by a "dodge" was a method to increase the serviceability of a component without changing the other basic production process. In the Merlin the pistons are Aluminium alloy, the big end beaings are lead bronze, the little ends are phosphor bronze, the con rods are nickel steel forgings, the crankshaft is a Ni Cr Mo steel hardened with nitrogen while the crank cases are Aluminium. The critical parts are either not steel at all or completely out with what people regard as "steel". I have worked with stainless "steels" where Iron is quoted as "balance" and Carbon is less than 0.03% even though steel is supposed to be an Iron Carbon alloy. They are actually Cr Ni Mo Fe alloys but "steel" is a convenient collective word.

When I worked in aerospace, there was one part where they changed the process, from air melt to vacuum melt, with absolutely no other process changes. The part went from severely life-limited (recommended replacement interval less than 500 flight hours) to unlimited: same part, same heat treat, same testing specs, same loads.

 

[pbehn]

When I worked in aerospace, there was one part where they changed the process, from air melt to vacuum melt, with absolutely no other process changes. The part went from severely life-limited (recommended replacement interval less than 500 flight hours) to unlimited: same part, same heat treat, same testing specs, same loads.

You do not have to go to aerospace applications or even to vacuum melting, good de gassing procedures on normal carbon steels lift Charpy (CV 10) impact values from 250/300 to 500+.Joules But the level of this discussion illustrates my point, what is a good or a bad steel depends entirely on what you want. The part you were quoting is not "bad" when produced by air melt method, it is just not as good as what replaced it, that is engineering and metallurgy..

 

[swampyankee]

You do not have to go to aerospace applications or even to vacuum melting, good de gassing procedures on normal carbon steels lift Charpy (CV 10) impact values from 250/300 to 500+.Joules But the level of this discussion illustrates my point, what is a good or a bad steel depends entirely on what you want. The part you were quoting is not "bad" when produced by air melt method, it is just not as good as what replaced it, that is engineering and metallurgy..

My only metals-related experience is when I did structural test (mostly fatigue testing) before I moved to aerodynamics; I prefer my anecdotes to be personal.

 

[pbehn]

My only metals-related experience is when I did structural test (mostly fatigue testing) before I moved to aerodynamics; I prefer my anecdotes to be personal.

Me too, and I appreciate it. The discussion hinges around "bad" steel. Having worked on steels for 35 years the term is not applicable. You have a steel that is acceptable to the specification or "fit for purpose" or it isn't. Basically you cannot say a crankshaft is good steel and so melt it down and make con rods and valves out of it.

 

[bobbysocks]

If you did this would more likely be a problem of oil feed, oil type or bearing quality. Various "dodges" like tuftriding and ball peening increased the service life of engine parts but this is not really a question of "bad steel". Some manufacturers have had problems in the past with things like valves and rings for example, this is usually poor heat treatment not the steel itself.

In my youth Honda had a problem with their 900cc engines breaking con rods when used for racing. The solution was to use a smaller not bigger "big end" housing. The smaller connecting rod being lighter put less load on the crank and bearings. Any layman would blame the steel used in the engine when in fact the problem was the engine design itself.

I agree. the problems would be more related to the lubrication in regards to the crank, cams, rings, and the parts of the engine that are related to them. the other aspect would be insufficient cooling....one part of the engine retaining too much heat and causing warpage or fracture. but both of those are engineering issues and not the steel, iron, metal itself.

bad metal would result in fracturing with sufficient cooling....excessive cylinder, valve guide, etc wear with sufficient lube....

the only problems I can recall were valve and valve seat issues, and sparkplug leading/fouling. others may and probably do have more info than i.

 

[swampyankee]

Me too, and I appreciate it. The discussion hinges around "bad" steel. Having worked on steels for 35 years the term is not applicable. You have a steel that is acceptable to the specification or "fit for purpose" or it isn't. Basically you cannot say a crankshaft is good steel and so melt it down and make con rods and valves out of it.

My point is that changes in processing can make a material (not just steel) suitable or not. I don't know what Rolls Royce's quality control methods were for materials and I don't know what kind of quality control checks they had during processing, nor the degree that these checks were enforced in subcontractors. I can only presume they were adequate for the design and within normal practice for aircraft manufacture at the time.