Stainless Steel Castings: Production Process and Uses

Stainless steel is a durable and versatile alloy that is used in a wide range of industries, including food processing, chemical processing, and medical equipment manufacturing. Stainless steel castings are components that are made by pouring molten stainless steel into a mould. This process allows for the production of complex shapes and parts that would be difficult or impossible to make using other methods.

Benefits of Stainless Steel

Stainless steel offers a variety of benefits, including:

  • Corrosion resistance: Stainless steel is highly resistant to corrosion, rust, and staining. This makes it ideal for use in environments where it will be exposed to moisture, chemicals, and other corrosive elements.
  • Heat resistance: Stainless steel has a high melting point and can withstand high temperatures without deforming or losing its strength. This makes it suitable for use in applications where it will be exposed to heat, such as kitchen equipment, industrial machinery, and aerospace components.
  • Strength and durability: Stainless steel is a very strong and durable material. It has a high tensile strength and can withstand heavy loads without deforming. Therefore it performs well when used in applications where strength and durability are important, such as construction materials, automotive parts, and medical implants.
  • Hygiene: Stainless steel is a non-porous material and does not support the growth of bacteria. This makes it common for use in food processing equipment, medical devices, and other applications where hygiene is important.
  • Easy to clean and maintain: Stainless steel is a low-maintenance material. It is easy to clean and disinfect, and it does not require painting or other special finishes.

In addition to these general benefits, the various grades of stainless steel also have a number of specific benefits depending on its composition. For example, austenitic stainless steels are highly ductile and can be easily formed into complex shapes. Ferritic stainless steels are magnetic and have superior corrosion resistance to austenitic stainless steels, although with the trade-off of lower mechanical properties. Martensitic stainless steels are the hardest and strongest type of stainless steel, but they are also the least corrosion resistant.

Raw Materials

The main raw materials required for the production of stainless steel castings are:

  • Stainless steel scrap,
  • Alloying elements such as ferro chromium, nickel briquettes, and ferro molybdenum – all of which can be purchased from Mineral-Loy.
  • Fluxing materials to remove impurities from the molten metal.

Production Process

The production process of stainless steel castings can be broken down into the following steps:

  1. Patternmaking: A pattern is made of the desired shape of the casting with allowance for contraction and possible machining. This pattern can be made from a variety of materials, such as wood, metal, or plastic.
  2. Mould making: A mould is made around the pattern using a variety of materials, such as sand or ceramic. The mould also contains the running and gating system to introduce the molten metal into the mould cavity in a controlled manner as well as the feeders used to counter-act shrinkage.
  3. Core making: Cores are used to create hollow cavities in the casting. Cores are typically made from sand or ceramic.
  4. Melting: The stainless steel scrap and alloying elements are melted in a furnace to the required composition.
  5. Pouring: The molten stainless steel is poured into the mould.
  6. Solidification: The molten stainless steel cools and solidifies inside the mould.
  7. Shakeout: The casting is removed from the mould.
  8. Fettling: The casting is cleaned, trimmed, and inspected.

Heat Treatment

Stainless steel castings often undergo heat treatment after they have been cast. Heat treatment is a process of selectively heating and cooling a metal to alter its microstructure and thus its properties. It is used to improve the strength, hardness, toughness, ductility, and corrosion resistance of metals.

The need for heat treatment arises because the microstructure of a metal can be affected by its composition, processing history, and cooling rate. For example, when a metal is cast, it will solidify with a coarse-grained structure that is often not homogenous in composition. This structure is typically weak and brittle. Heat treatment can be used to refine the grain structure, which can improve the strength and ductility of the metal.

Heat treatment is also used to produce specific properties in metals. For example, stainless steel castings can be heat treated to improve their corrosion resistance. This is done by heating the casting to a high temperature and then rapidly quenching it. This high temperature process dissolves carbides in the stainless steel, which makes it more resistant to corrosion.