Alloys of iron, carbon and silicon where carbon is present in excess of the amount which can be retained in solid solution are termed cast irons.

The common engineering grades contain Carbon in the form of flake graphite, but this can be modified with additions to a spheroidal shape. This imparts major improvements in strength and ductility and the alloys are then called SG, Nodular or Ductile irons (N1-N5).

Additions of nickel and chromium change the structure to produce the wear resisting alloy Ni Hard (Q51-Q52), while higher amounts of these elements yield the excellent corrosion resistance of the Ni Resist Family (R10-R13).

From a low carbon iron for electro-magnetic applications (S1), our range of low carbon steels (S3, S4) can be produced to meet specific strength and hardness requirements. Higher hardenability, wear resistance and sub-zero impact criteria are achieved through minor alloying additions and precise heat treatment control (R60-R67).

An additional series of steels resistant to high temperature creep is developed by alloying low and medium carbon steels with chromium, molybdenum, vanadium and tungsten (R68-R72). Nickel is added to many of these grades to improve sub-zero impact properties (R66).

CORROSION RESISTANT STEELS

HEAT RESISTANT STEELS

Martensitic

A protective passive oxide film can develop on steels with chromium contents above 12%, imparting to these steels "stainless" characteristics. By maintaining a suitable composition balance between carbon and chromium, a series of high strength stainless steels are produced (R23-R23XHC).

Components cast in these allows meet specific hardness and wear resistance criteria through closely controlled heat treatment practices. Material toughness and versatility are enhanced by additions of nickel and molybdenum (R24).

Precipitation Handling

Strength and corrosion resistance superior to many martensitic stainless steel alloys is achieved by precipitation hardening a low carbon martensitic or semi-martensitic stainless steel (R27-R28). This is accomplished by accurate alloying and a low temperature heat treatment, allowing machined parts to be age hardened with only minimal distortion and scaling. Depending upon the particular material composition and heat treatment programme, precipitation hardening stainless steels can be supplied with appropriate hardness differentials to avoid galling and seizing during metal to metal contact.

Austenitic

Austenitic stainless steels are very tough and essentially non-magnetic materials that are alloyed to produce resistance to corrosion in a variety of environments.

The basic 18% chromium/10% nickel grade (R31) has a very good corrosion resistance in many applications. This alloy can be refined (R31LC) or alloyed with molybdenum (R33,R34) for enhanced corrosion resistance or modified for improved welding (R30) and machining (R32) characteristics. Increasing nickel content and alloying with molybdenum and copper results in greatly improved corrosion resistance in more aggressive environments such as hot sulphuric acid (R36,R37).

Duplex

Duplex stainless steels comprise a mixture of ferrite and austenite, producing a material with many of the advantages offered by both structures (R29). They generally have comparable or better corrosion resistance to austenitic steels, with more than twice the yield strength, and are especially resistant to pitting corrosion and stress corrosion cracking in chloride environments.

Duplex alloys are made to a wide range of internationally recognised and proprietary specifications, through precise control of alloying content of both primary and trace elements and tailored heat treatment. Thus a series of duplex alloys develops with each grade processing specific characteristics such as Pitting Resistance Equivalent, yield strength and ferrite austenite ratio to suit a particular application.

Steel alloys containing more than 20% chromium produce a protective, sustainable surface scale when exposed to high temperatures in oxidising atmospheres up to 1100 degrees C. When nickel and carbon are added to these alloys, a series of heat resisting alloys is produced to perform in an array of high temperature applications.

Increased nickel content progressively stabilises austenite in heat resisting steels, from a duplex structure especially designed for sulfurous environments (R80), through alloys with measured ferrite/austenite ratios (R81,R83), to fully austenitic alloys (R84, R85). By adjusting nickel, chromium and carbon content and including additions of rare earth elements, niobium and tungsten, castings can be manufactured to withstand high temperature thermal cycling, carburising and high load environments.

In more severe applications, a series of grades with substantially increased nickel contents are used (R87,R88). Generally, these super alloys contain additions of one or a combination of rare earths, niobium, tungsten and cobalt (R87Nb, R88Nb,R89). This produces an alloy that is able to absorb considerable amounts of carbon over long periods without significant embrittlement.

The 99.5% cast nickel grade (R48) is designed to resist hot caustic solutions and can be alloyed to increase strength. Nickel-copper Monel type alloys (R47) have very good resistance to chloride corrosion. This grade can be supplied with additional silicon and age hardened (R47S) for increased strength where erosion-corrosion and galling occur in chloride containing media. The nickel-molybdenum-chromium (R39) Hastelloy type grades provide unique corrosion resistance to hydrochloric, phosphoric and hydrofluoric acid. QC R39 can additionally be alloyed with one or a combination of tungsten, vanadium, niobium, copper, tin and bismuth to produce metals with increased strength, high temperature capabilities, improved corrosion resistance and anti-galling properties.