Carbon Steel Investment Casting and its Applications in Industrial Equipment - Impro Precision


Carbon Steel Investment Casting and its Applications in Industrial Equipment

August 9th, 2023

Cranks, handles, levers, rods and shafts are just some of the industrial equipment parts cast in carbon steel. Casting helps avoid machining, and investment casting achieves this better than sand casting. This blog discusses the benefits of investment casting parts for industrial equipment and explains why you should consider it for your next project.

About Carbon Steel

Carbon steel is steel with minimal alloying elements. It’s just iron with 0.05 – 2.00% carbon. Below 0.2% carbon it’s considered low carbon steel. Widely used 1020 steel is a good example. It’s ductile, machinable and weldable.

When carbon content is in the range of 0.2 – 0.5% steel is considered a mid-carbon steel. Hardness and strength are higher, and unlike the low carbon steels, mid-carbon steel can have strength and hardness raised further by heat treatment. Machinability and ductility are not as good as that of low carbon steel though. An example of a mid-carbon steel is 1050.

Above 0.5% carbon content, steel is harder and stronger still. However, ductility and machinability are reduced.

Carbon steels have good castability. They flow well and solidify over a narrow temperature range, which ensures consistency and minimizes defects.

Benefits of Investment Casting

The investment casting process is capable of higher accuracy than sand casting and reproduces thin sections and fine detail. Surface finish is excellent. To quantify these claims:

  • The ISO accuracy grade for investment casting is CT4 to CT8
    • Translates to 0.007 – 0.055”/linear inch
  • In practice, linear accuracy of 0.005”/linear inch is usually achievable
  • Surface finishes of 125 – 250 μ” are achievable

This precision and finish reduces the need for machining. Internal surfaces such as bores in valve bodies and the insides of housings can often be left in the as-cast condition rather than undergoing costly machining.

Investment Casting Considerations

Investment casting is an expendable mold process, and mold production requires multiple steps. These are:

  • Mold a wax pattern with cores, as dictated by final part design
  • Assemble wax patterns onto a wax sprue or runner that will form the metal delivery system
  • Build up a ceramic coating on the wax and allow it to dry
  • Melt out the wax pattern to leave a cavity in the ceramic shell
  • Pour molten metal into the ceramic shell and allow to solidify
  • Break away the ceramic shell and cut the individual parts from the runner/sprue system

This complexity extends the lead time for getting first production parts. However, once tooling is proven and accepted, parts produced by the investment casting process are very consistent with a low level of defects.

Cooling and solidification rates during casting are influenced by section thickness and local mass. This can lead to differences in strength, hardness and ductility within a casting. However, with investment casting it’s possible to minimize this effect by making local adjustments in the thickness of the shell.

Reasons for Investment Casting Industrial Equipment Parts in Carbon Steel

Parts made by investment casting are very close to final or net shape. This reduces machining, which can otherwise be slow and costly, especially when the geometry requires multiple setups. Reduced machining is always beneficial but the savings increase when machinability is less good, as is the case with the medium and high-carbon grades of steel.

Talk to Investment Casting Specialists

The benefits from investment casting are magnified by complex part geometries. These increase the savings in machining and so help lower total cost. Alternatively, it might be argued that investment casting enables cost-effective production of more complex geometries, so allowing improved properties and part performance.

Industrial equipment typically incorporates large numbers of parts produced in carbon steel. Examples include:

  • Housings
  • Shafts
  • Levers
  • Rods
  • Linkages
  • Other parts for complex mechanisms

Impro is a leader in investment casting a long list of alloys that includes carbon steel. If you’re looking for a source of high quality parts for industrial equipment, cast in carbon steel, we can help. Contact us to start that discussion.


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