Alloy cast steel - what are its properties, features and application?

Cast steels are one of the most important as well as the most popular materials used in foundry. They are characterized by exceptional strength and wear resistance, which makes them irreplaceable both in the production of many machine elements and tools. In this article, we will focus on alloy cast steel.

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In this article you will learn:

• what is alloy cast steel and how is it produced,
• what are the most popular additives to this alloy
• what are the types of it,
• where is the application for this type of cast steel.

Alloy cast steel

Alloy cast steels – as in the case of alloy cast irons, which we wrote about a week ago – are cast steels to which alloying elements are introduced in order to give them the desired properties suitable for specific casting applications. The alloying elements that are used most often are, among others:

• nickel,
• chrome,
• silicon,
• manganese,
• molybdenum,
• vanadium,
• tungsten,
• titanium,
• niobium,
• cobalt,
• boron,
• and other.

Production

How is it produced? Cast steel is currently obtained in arc or induction furnaces. In the case of alloy cast steel, in addition to the addition of carbon, the content of which does not exceed 1.5%, additional alloying admixtures are added to the cast steel.

Types of alloy cast steels

Alloy cast steels can be divided into subtypes due to the content of alloying additives and due to applications.

Division due to the content of alloy additives

This type of steel alloy is divided into three subtypes, depending on the content of alloying additives.

• low-alloy steel castings, i.e. ones in which the total concentration of additives does not exceed 2.5%. This group of cast steels includes, among others, alloy cast steel for operation at elevated temperatures and medium carbon structural alloy cast steel.
• medium-alloy steel castings, with additives in the concentration range of 2.5-5%, depending on their quantity and composition, having the desired characteristics of low-alloy and high-alloy cast steels.
• high-alloy steel castings, with additives concentration above 5%. High-alloy cast steel is, for example, wear-resistant and tool-resistant cast steel with special properties.

Division due to application

Alloy cast steels can also be divided due to their properties. In this case, we distinguish:

• corrosion-resistant cast steel, i.e. one that is resistant to oxidation when exposed to, for example, water or chemicals,
• heat-resistant and creep-resistant cast steel, which is a material with the ability to work at temperatures above 650˙C, resistant to the destructive effects of heated gasses,
• cast steel for construction and machinery, which includes general-purpose alloy cast steel, cast steel for work under pressure both at low and room and elevated temperatures, wear-resistant cast steel,
• cast steel for tools, and therefore used in the production of tools with specific properties, such as crushing balls and wear rings for coal mills.

Chemical composition of alloy cast steel - additives

Alloy cast steel owes its particular applications to certain alloying elements, which, when used in the right amount and proportion, ensure optimal properties.

Alloying elements affect the microstructure of cast steel in the same way as in steels, but in the case of cast steel, their influence on technological (casting) properties should be taken into account.

Odlewnictwo, wyd. Naukowo-Techniczne (own translation)

Below we will describe some of the additives used in the production of this cast steels and their properties.

Manganese

• ensures good castability,
• reduces casting shrinkage,
• 12➗14% content makes the cast steel harden under the influence of deformation,
• increases impact, abrasion and tensile strength.

Chrome

• contributes to increasing the density of cast steel,
• increases sensitivity to non-metallic inclusions (which are a frequent cause of cracks in castings,
• increases resistance to hot gasses,
• guarantees heat resistance and creep resistance,
• increases corrosion resistance.

Silicon:

• increases the density of cast steel,
• increases brittleness,

Nickel

• increases corrosion resistance,
• lowers the quenching speed (thus facilitating the quenching process),
• dissolved in ferrite increases impact resistance.

Application

The exact application of this alloys is directly related to the properties of the particular alloy. And so it is used, for example, in construction, mechanical and machine applications in projects with a wide spectrum of needs.

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