The use of stainless steels

The use of stainless steels is very wide: from heavy industry and energy production to precision mechanics and electronics. In Europe, typical main application areas are construction and architecture, the food industry, environmental protection, household appliances, the chemical industry, the pulp and paper industry, the pharmaceutical industry, energy production and the automotive industry.

Stainless steel was invented in 1912, but nearly 100 years had to pass before it was ‘noticed’ in construction and architecture. It is a material that is extremely durable and practical, and at the same time noble and elegant. Thanks to the variety of types and types of surfaces and a wide range of products, it is able to meet the most sophisticated requirements set for building and finishing materials by architects and interior decorators.

Column covers, pool fittings, railings, lifts (cabins) are just a few examples of the use of stainless steel in construction. It has been combined with wood or glass very often recently. One of the more famous examples are the two Twin Towers in Kuala Lumpur and the Sony Center in Berlin.

In addition to very high corrosion resistance, the advantages of stainless steel include, among others:

• a wide range of available steel products and products (e.g. sheets, pipes, profiles, bars, flat bars, angles, ropes),
• a large selection of surface types (from polished, through mirror, matt, with embossed or etched patterns, ending with colored surfaces),
• a multitude of available species with different properties,
• easy to form, process and connect,
• strength and stiffness of the material,
• low thermal expansion,
• high melting point (much higher fire resistance than other steels),
• incomparably greater durability of stainless steel compared to other finishing materials.

In addition to glass and some plastics, stainless steel is currently one of the few materials that is approved as a material for making equipment for the storage, processing and transportation of food. High demands on hygiene, toxicity, efficiency and even appearance are the rule in the food industry.

The requirements for the quality of the final products are very high, both at the stage of raw material sources, through the processing process and ending with us, the consumer. Not so long ago, the issue of the solubility of heavy metals from equipment in contact with food was not at all discussed. Now there are relevant European recommendations, e.g. for the amount of nickel or dissolved chromium in stainless steel.

Most of the energy these days is obtained by burning fossil products (coal, oil and gas) or by nuclear power plants. In any case of energy production, stainless steel is essential.

From the production of gas or oil, both onshore and offshore, to plants that burn and produce electricity (including nuclear power plants), stainless steel is everywhere. The stainless steel grades used in this industry are almost always special high-alloy steels, the requirements of which, both in terms of testing and certification, are very strict.

Most of the equipment used in pulp and paper mills is also made of stainless steel. In this case, the minimum grade used is EN 1.4401, although in modern plants (closed liquid circuit) this grade is usually insufficient and grades with a higher molybdenum content (minimum 3-6%) must be used. As in the case of the chemical industry, only specialists should select the appropriate grade.

Speaking of the use of stainless steels, one must not forget about the chemical industry, where practically all equipment (vessels, pipes, tanks, reactors, etc.) is made of austenitic stainless steel. The minimum grade is EN 1.4404, however, very often used are high-alloy grades with a high molybdenum content, up to 6%. In this industry, selecting the type of stainless steel (grade) is an extremely difficult task and requires a lot of experience.

Not only at work or watching reports from the opening of a new petrochemical plant, but also at home, we more and more often find products made of stainless steel or with stainless steel elements. Both in the kitchen by opening a cupboard with pots or bowls, or by reaching for the simplest tools (e.g. a knife, fork). Most automatic washing machine drums, internal parts of dishwashers and, increasingly, cookers and ovens are made of stainless steel.

Stainless steel as a material has even become synonymous with a high standard of living. Visible in our homes are also references to it (as a noble material), an example is the trend in the colors of RTV equipment (silver, designed to resemble stainless steel).

As a rule, modern technologies currently go hand in hand with ecology and environmental protection. It is similar with stainless steel. Starting with the durability of this raw material, which is not insignificant, most of the old existing plants that are subject to reconstruction and modernization (e.g. closed water circulation, gas cleaning) require the use of stainless steel. In the case of new plants, already at the design stage, it is assumed that stainless steels will be used in order to meet the existing environmental protection requirements.

Considering the wide use of stainless steel, it could not be missing in transport. It is a powerful market for stainless steel both on land and at sea.

The necessity to transport various types of materials, goods and liquids increases every year with a simultaneous trend of minimizing costs and ensuring safety. The answer to this are properly designed, usually multi-purpose, stainless steel containers and tanks. Multi-purpose, because thanks to the properties of the raw material from which they are made, they can both transport food raw materials (e.g. milk), and then chemical products (e.g. solvent). Of course, after the transport of one product or liquid, the containers just need to be cleaned and disinfected.

In the automotive industry, the greatest use is in the part of the car that we rarely pay attention to – exhaust pipes and catalytic converter pipes. They are made of both austenitic and ferritic grades. Nevertheless, by adding up the stainless steel used in the production of the car, we get a value of about 10-20 kg.

As a curiosity, however, we can recall the DeLorean DMC 12 sports car produced by the DeLorean Motor Company in the years 1981 – 1983. What may interest us about it, and at the same time is its characteristic feature, was the stainless steel body. Important fact – by 1983 about 9,200 DMC-12s were produced, about 6,000 (!) Survived until 2005.

Examples of the use of the most popular types of stainless steel on the market:

• PN-H17 / AISI 430 (welding not recommended)
  • decorative elements of devices, in particular in the refrigeration industry (e.g. due to magnetic properties)
  • in the production of household appliances (e.g. automatic washing machine drums)
  • in the food industry (e.g. pasteurizers, tanks for food products)
• PN-0H18N9 / AISI 304 (weldable, for deep-drawn parts)
  • in the chemical industry (e.g. acid tanks, industrial pipelines)
  • in refineries and petrochemical plants
  • in the food industry (e.g. parts of technological lines in dairies, breweries, or elements exposed to preservatives)
  • in the pulp and paper industry
  • in the paint and pharmaceutical industries
  • ship and air constructions as well as equipment for ships and railway carriages
  • decorations, interior architecture, small architecture.
• PN-00H17N14M2 / AISI 316L (weldable; do not use in the presence of nitric acid)
  • used in the production of chimney liners
  • in the food industry (e.g. in dairies, breweries)
  • in the pharmaceutical industry (including components for hygienic processes such as centrifugal pumps)
  • in the pulp and paper industry (practically all equipment, including pipelines, washers, etc.)
  • in the shipbuilding industry (in shipbuilding and ship equipment)
• PN-H17N13M2T / AISI 316Ti (weldable)
  • in the chemical industry, refineries, petrochemical plants (e.g. pipelines)
  • in the pharmaceutical industry (e.g. pressure transmitters)
  • in the textile industry
  • in the shipbuilding industry (e.g. chemical tanker holds, hydrostatic probes)

Any suggestions regarding the use of steel or machining are for reference only. Detailed technical information (including chemical composition) is contained in the relevant standards (PN, EN, ISO, DIN, ASTM).