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Possible dumb question, which steel to replace cast iron?

Richard/SIA

Cast Iron
Joined
May 13, 2007
Location
No. Nevada
Trying to find niche items to make with my soon to arrive small VMC.
It seems a lot of heavy equipment wear parts are NLA at fifteen years old, or even less.
Just old enough that they are on the second owner and not practical to drop $12K-$20K for repair of what should have been a relatively inexpensive item if it were still available.
Of course I will not have access to original castings, and I know that making just one as needed is impractical.
So looking for short runs to fill a definite but niche market.
Sorry, long explanation for the simple question.
Which steel would be most suitable to machine in place of the cast iron most of these items originally used?
These are items like steering knuckles for front end loaders.
 
Tractor housings are mostly nodular iron if made since the 1960s ...........and having fixed heavy equipment since the 1960s,I have never noticed any cheap OEM parts......unless you refer to used salvage parts...........anyhoo ,anything made of steel will be made of high strength alloy steel ,and hardened and tempered..............unless you restrict yourself to garden tractors ...........At one time I did make stuff like the centre pins and bushes for articulted loaders .....but these were cheapo will fit stuff for dealers to fit to used machines ............I very much doubt they gave 10% of the life of new OEM parts.
 
Okay, with a wide variety of prematurely "Obsolete" parts being needed by those who are small operations/independent owner operator guys, I know there is an unfilled market.
I cannot say for certain that I will be capable of filling it but do think it may be worth exploring.
OEM semi-consumable parts are being dropped from production at increasingly short intervals, remaining stock is quickly exhausted.
What had been an OEM $1,500 parts becomes a $12,000 part when the only way to get it is to buy a complete refurbished assembly from a specialist.
Hardening and tempering services should be available despite my probably having to travel for them.
So it seems I need to source nodular iron if it may be had in blocks.
 
Your question is a bit like "how long is a piece of string?".
Maybe some pics of the parts you're thinking about would help.

The reason OEM's use cast iron is economics. They need a part of a certain shape to do a particular function. Cast iron, be it nodular, or whatever, is a very economic method to produce a shape in large quantities.
Another method is forging steel to the shape. Generally a more expensive process, but can be appropriate to meet strength requirements.
I had a leaf spring hanger bracket break on a 5 ton truck. Original material was cast iron, probably maleable iron. I replaced it with an A36 steel fabrication.

Select a steel of similar physical properties to the material being replaced.
 
In the 1980s ,earthmover makers went hog wild over large castings made of nodular iron.........the catch ---or maybe the intention---- was the castings couldnt be welded ........not that this was ever stated specifically .....generally ,just the "nodular iron" logo was cast into them..........J I Case in particular went crazy over castings that wernt fixable.
 
I have use ductile iron in place of cast iron for a few things. But I think John K is spot on about what you are faced with with on replacements.
 
Which steel would be most suitable to machine in place of the cast iron most of these items originally used?
These are items like steering knuckles for front end loaders.
Steering components are almost never cast iron!! Even suggesting making them from iron is akin to placing your head in a nuse, as lawsuits would be easily won in the event of a failure of such a part, if injury occurred as a result.

Do yourself a big favor and study carefully on alloys and iron types and their common uses. There's a lot to learn, but if you want to be a machinist, it'll save your rear end from a good swift kick. ( and likely worse troubles)

If you want to reproduce any component for any machine, you first have to get a very well educated idea of what was used originally. No wild guessing!!

Steering joint components have been made of forgings for over 100 years now for it's strength, even most modern steel alloys cannot supply the strength needed without forging it. Some high end steels can be used with proper selection, machining processes and exacting heat treatments. But these steel alloys are VERY expensive.

I'm not saying any of this to be insulting, but rather a stern warning. Part failure due to bad parts can have massive legal repercussions. Even if it's just on Billy Bob's yard tractor. Homework can help reduce those chances greatly.

I'm sure many here can offer favorite books on the subject of metal selection.
 
Steering components are almost never cast iron!! Even suggesting making them from iron is akin to placing your head in a nuse, as lawsuits would be easily won in the event of a failure of such a part, if injury occurred as a result.

Do yourself a big favor and study carefully on alloys and iron types and their common uses. There's a lot to learn, but if you want to be a machinist, it'll save your rear end from a good swift kick. ( and likely worse troubles)

If you want to reproduce any component for any machine, you first have to get a very well educated idea of what was used originally. No wild guessing!!

Steering joint components have been made of forgings for over 100 years now for it's strength, even most modern steel alloys cannot supply the strength needed without forging it. Some high end steels can be used with proper selection, machining processes and exacting heat treatments. But these steel alloys are VERY expensive.

I'm not saying any of this to be insulting, but rather a stern warning. Part failure due to bad parts can have massive legal repercussions. Even if it's just on Billy Bob's yard tractor. Homework can help reduce those chances greatly.

I'm sure many here can offer favorite books on the subject of metal selection.
Spot on. Drawings for these components will have large cap letters in a box S.R.C.. safety related components! Screw it up and you get to meet a bunch of lawyers.
An added complication…Steering knuckles up to 20000# are forged and made from 4135. Q&T to 300BHN. Only midrange to upper end chemistry can achieve this. Making them from a block won’t have the grain flow or grain size. It would be a failure waiting to happen.
 
In fact .Case used nodular iron for the whole front axle and steering knuckle of tractors and backhoes after about 1970 ........and they included another clever wheeze .........the previously through drilled kingpin was left solid ,which meant those greasing the top of the kingpin as had always done ,were faced with failure of the lower bearing ,which would break the 'ear ' off the axle casting .....no worries ,weld it back on again ...and it would just break off again .
 
The crystal structure of a cast item is way different from a wrought product, it is similar to a cast steel , kind of on the spectrum.
When you cast, iron or steel or any metal, there’s the initial chill crystal structure, then more crystals called dendrites form, they form in the direction or opposite direction to the direction of the flow of heat or thermal extraction, starts quick but slows as heat takes time to move, the stuff that’s still liquid now enclosed gradually cools to the point that another type of crystal forms, heat is now moving out from all directions so the crystals have to form devoid of orientation, this is the equiaxed area, small crystals that grow till the boundary hits another then stops, crap that is higher melding lower solubility etc is pushed along by the boundary.
This stuff gets trapped in between like manganese sulphide for example.
Cast things are usually brittle,
That’s brief, there are probably hundreds if not thousands of books describing the processes.
In steel you then reheat and roll or forge, this squishes and stretches the structure, metallurgy is finding all sorts out all the time.
As a rule cast brittle, wrought ductile, cast stiff, wrought bendy.
Mark
 
These are items like steering knuckles for front end loaders.
Highly stressed components such as these are almost certainly NOT cast iron. I would start under the assumption that they are cast steel. You had better know your metallurgy and heat treatment processes before venturing into the production of these parts.
 
The crystal structure of a cast item is way different from a wrought product, it is similar to a cast steel , kind of on the spectrum.
When you cast, iron or steel or any metal, there’s the initial chill crystal structure, then more crystals called dendrites form, they form in the direction or opposite direction to the direction of the flow of heat or thermal extraction, starts quick but slows as heat takes time to move, the stuff that’s still liquid now enclosed gradually cools to the point that another type of crystal forms, heat is now moving out from all directions so the crystals have to form devoid of orientation, this is the equiaxed area, small crystals that grow till the boundary hits another then stops, crap that is higher melding lower solubility etc is pushed along by the boundary.
This stuff gets trapped in between like manganese sulphide for example.
Cast things are usually brittle,
That’s brief, there are probably hundreds if not thousands of books describing the processes.
In steel you then reheat and roll or forge, this squishes and stretches the structure, metallurgy is finding all sorts out all the time.
As a rule cast brittle, wrought ductile, cast stiff, wrought bendy.
Mark

I think the discussion above and in other posts suggesting cast iron is brittle is true for grey cast iron. However, ductile cast iron is so named for a reason. It is used in highly stressed parts (Particularly steering knuckles) and does not fail by simple fracture anywhere nearly as likely as grey iron.

"Ductile iron is used in many industrial applications because of its strength, ductility, and resistance to impact. Here are some common applications for ductile iron:
  • Pipe: Ductile iron pipe is used for water and sewer lines, as well as for wastewater and sewage
  • Automotive components: Ductile iron is used in vehicle gears and suspension components, brakes and valves, pumps and hydraulic parts, and housings for wind turbines
  • Agricultural tractors: Ductile iron is used in the rear axle shells of agricultural vehicles
  • Impact protection: Ductile iron is safe to use in bollards because it doesn't fracture like gray iron
  • Grand piano harps: Ductile iron is used for the iron plates to which high-tension piano strings are attached

    Other applications for ductile iron include:
    • Cable drums
    • Frames
    • Gear boxes
    • Hubs and machine frames for the wind power industry
    • Steering knuckles
    • differential housings
      Vises: Ductile iron is used instead of regular cast iron or steel

      Here is a link specific to ductile iron steering knuckle machining
    Ductile Steering Knuckle
  • Denis
 
Highly stressed components such as these are almost certainly NOT cast iron. I would start under the assumption that they are cast steel. You had better know your metallurgy and heat treatment processes before venturing into the production of these parts.

^Nailed it with the knowing metallurgy for big business.

My cell rings with a frantic call one day from a big maker of yellow wheel loaders etc in the usa. You gotta come here quick we have some new loaders for shipment and the axles are snapping off just sitting there. As I know the guys my response was like yeah, mine's a foot long too.

I visit and sniff around knowing the parts are hardened on my competitors machine. And yup, these 8 inch diameter axles are snapping right off. An established part and process, new problem so that makes it easier.
Watching process the induction machine runs as setup. But!!! They are using a different induction coil that overheated the flange. And, someone changed the quenchant type. The temper cycle didn't help with these errors and there was a ton of retained stresses. So sitting in a lot after a week waiting to be prepped for a railroad car, the stresses were too much and your 8 foot tall tire is now laying flat on the ground.

*I did get the next few sales for equipment.
 








 
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