Materials

Nickel based alloys are characterized by high toughness, and good resistance to oxidation and corrosion. Alloying additions to the base nickel content creates grades that vary in the relative range of the these characteristics, which imparting good mechanical strength and high temperature properties.

For the manufacture of these grades, voestalpine companies worldwide are known as the world leader in melting and remelting technology. Our 120-years of experience plus our metallurgy know-how and a focus on the development and production of high performance materials have meant we have become one of the most innovative producers of special steel in the world. Our company boasts the most modern vacuum induction melting (VIM) and vacuum arc remelting units (VAR) plus pressurized electroslag remelting units (PESR).

The properties of duplex stainless steels are achieved with overall lower alloy content than similar-performing super-austenitic grades, making their use cost-effective for many applications. Duplex grades are characterized into groups based on their alloy content and corrosion resistance.

Stainless alloys are divided into four basic groups: martensitic stainless steels, ferritic stainless steels, austenitic stainless steels, and precipitation hardening stainless steels.

When nickel is added, for instance, the austenite structure of iron is stabilized. This crystal structure makes such steels virtually non-magnetic and less brittle at low temperatures. For greater hardness and strength, more carbon is added, and these grades are defined as ferritic or martensitic alloys.

The ferritic types achieve moderate increases in strength by cold working. The martensitic types become martensitic during heat treatment and achieve excellent strength.

Austenitic stainless steel is one of the five classes of stainless steel by crystalline structure (along with ferritic, martensitic, duplex and precipitation hardened). Its primary crystalline structure is austenite (face-centered cubic). These steels usually cannot be hardened by heat treatment and are non-magnetic. This structure is achieved by adding enough austenite stabilizing elements such as nickel, manganese and nitrogen.

Like the austenitic stainless steels, the super austenitic stainless steels are also very ductile; they have excellent toughness, high strength, excellent corrosion resistance, good weldability and excellent formability. The super austenitic stainless steels are generally used where higher corrosion resistance, especially protection against chloride pitting and crevice corrosion, is required. Super austenitic stainless steels are defined as austenitic iron-based alloys with a PREN value greater than 40.

Viewing the microstructure respectively the chemical analysis the heat-resistant steels can be divided in the group of ferritic, martensitic, austenitic steels and nickel alloys.

Such steels are generally used in applications where resistance to increased temperatures are critical. These steels are hard wearing and offer a resistance to large variations in temperature. Industrial applications include furnaces, heat exchanges and incinerators where temperatures can reach up to 1100°C.

Characteristics include corrosive resistance, creep resistance, oxidation resistance and hydrogen brittleness – all under extremely high temperatures.

Creep resistant steels are steels designed to withstand a constant load at high temperatures.

The most important application of creep resistant steels is components of steam power plants operating at elevated temperatures (boilers, turbines, steam lines).

Precipitation hardening alloys of the 17-4 PH and 15-5 PH types achieve their strength by dissolving precipitates by solution annealing. An aging cycle then creates precipitates that strengthen the steel. They are usually characterized by extremely good corrosion resistance.

Engineering steels are basically wrought steels intended for mechanical engineering and related technical applications. These require critical and often stringent levels of elasticity, strength, ductility, toughness and fatigue resistance. In some cases, resistance to high or low temperatures, expansion, corrosive and other aggressive environments may also be required.

Each material is carefully tailored to meet specific user requirements for properties and performance, and in some cases, to facilitate manufacturing and fabrication techniques. These techniques are then used to manufacture components or parts. The composition, process flow and heat treatment parameters are carefully selected to meet customer needs.

This material group shows special physical properties such as thermal expansion, permeability, relaxation, heat transfer, electric resistance or density.

Titanium and titanium alloys are suitable for several applications. They offer good corrosion and erosion resistance, high strength, extreme mechanical and thermal stress resistance and good biocompatibility at low density.