The ABC of Stainless Steel

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It has now been over 2,500 years since humans were able to process iron for the first time. Since then a lot has happened. The wrought iron of that time has been transformed into the high-performance steel of today through ever new processes and further processing steps.

In the meantime, steel production has become a science in its own right - and like any science, metallurgy also involves many technical terms. We have put together this glossary so that you can look up a term quickly or simply expand your knowledge of all things steel.


adjustage The adjustage includes all work steps that are necessary to finish the product. This includes, for example, straightening, sawing or pickling.
alloy elements Alloy elements are all those elements that can be added to a metal, i.e. alloyed. Alloying always serves to improve the material properties.

The most important metallic alloying elements are:

Aluminum (Al)
Beryllium (Be)
Chromium (Cr)
Cobalt (Co)
Copper (Cu)
Manganese (Mn)
Molybdenum (Mo)
Nickel (Ni)
Niobium (Nb)
Tantalum (Ta)
Titanium (Ti)
Vanadium (V)
Tungsten (W)

Important non-metallic alloying elements are:

Carbon (C)
Silicon (Si)
Nitrogen (N)
annealing Annealing is one of the methods of heat treatment. A workpiece goes through the phases of heating and cooling in order to change its material properties in a targeted manner.

The three phases in detail:

1. Warming up
In the warm-up phase, the workpiece is brought to the holding temperature.

2. Hold
In the holding phase, the workpiece is held at a constant temperature for a precisely measured period of time
Charpy impact test The Charpy impact test is used to determine the toughness of a material. This property is important in the case of sudden loads and can be carried out practically with a notched hammer. The behavior of the material can be significantly different than when there is a static load, such as a tensile test.
corrosion Corrosion is the name given to the chemical reaction of a metal material with its environment (self-corrosion), with ion-conducting materials (contact corrosion) or as a result of a stray current (stray current corrosion).
degree of purity The degree of purity of steel is a measure of the content of non-metallic inclusions in the form of sulfides and oxides.
DIN 50602 distinguishes between two methods for determining it:

According to method M, the maximum inclusion size is determined and then classified. These purity classes range from class 0 (no inclusions) to 8 (large inclusions).

According to method K, a size index is determined, which is included in a cumulative parameter. This is indicated, for example, as K 4 oxide = 25 or K 4 sulfide = 42.

The degree of purity is always determined on a polished section under a light microscope with a magnification of 100: 1.
drawing Drawing is one of the cold forming processes and serves different purposes. These are in particular: reducing diameter and wall thickness, improving surface quality or strength, improving dimensional tolerances or creating the profile shape.
Basically, a distinction is made between rod, pipe and wire drawing.

In several pulls - depending on the initial cross-section of the workpiece - the material to be drawn is drawn through a shaping tool, such as a die, a drawing nozzle or a drawing hole.

Before drawing, it is necessary to thoroughly clean the surface of the drawing material by pickling or blasting descaling
flat rolling block Corrosion leads to a measurable change in the material that is usually visible to the naked eye.
forming Forming belongs to the six main groups of manufacturing processes (DIN 8580). Their most important processes are rolling, open die forging, drop forging, deep drawing, extrusion, extrusion and bending.
hardening Hardening means increasing the mechanical resistance of the steel. This is done through a targeted change in its structure. A distinction is made between transformation hardening, precipitation hardening and the increase in hardness through strain hardening.
hardness Hardness is a measure of the mechanical resistance that a body opposes to the penetration of a test body.
non-destructive testing Non-destructive testing means that the suitability of the material or test item is not influenced or reduced in any way during a test application. In contrast, there is the destructive testing of materials.
oxidation Oxidation is the loss of electrons from an atom, molecule or ion in the course of a chemical reaction.
pickling Pickling is a chemical process used to treat surfaces. The oxide or rust layer adhering to the surface is removed. The pickling creates a scale-free, metallic surface.
powder metallurgy Powder metallurgy is used to manufacture near-net-shape molded parts from iron-containing powders by pressing and sintering. The properties of a material, for example its porosity, strength or surface quality, can be significantly influenced by different powder compositions. Furthermore, it is possible to combine materials that would not be miscible under other circumstances.
rolling Rolling is one of the manufacturing processes from the pressure forming group. The aim is usually to reduce the cross-section of a material.
Rolling above the recrystallization temperature of the material is called hot rolling, below it it is called cold rolling.
roughness value Ra The Ra value (arithmetic average roughness value Ra) is a measure of the roughness of a technical surface (e.g. steel) that was produced, for example, by machining or forming processes. The mean roughness value is given in micrometers (µm). The roughness values range from 25 µm for very rough surfaces with noticeable grooves to 0.1 µm with machining marks that are no longer visible.
sawing Sawing refers to the cutting of, for example, profile steel, steel bars or steel pipes using a circular or band saw. The cutting movement is either circular (circular saw) or straight (band saw).

The circular saw works at a high cutting speed and is mainly used for heavy cuts. The cuts can be made straight or at right angles to the rod axis or as miter cuts. With the band saw, on the other hand, contour cuts can be made due to the maneuverability of the narrow saw band.
scale Scale is the term used for iron oxides, which are formed when steel is heated by a reaction between the oxygen and the iron on the hot metal surface.
straightening When straightening, bars that are not sufficiently straight or warped are restored to an acceptable shape. This is done by bending on a roller straightening machine, by stretching on a stretch-straightening system or by pressing on a straightening press.
structure The structure, also called microstructure, describes the internal structure of the steel. It largely determines its mechanical and chemical properties and can be specifically influenced by forming and heat treatment.
surface defects Surface defect is a collective term for: bubbles, pores, overrolling, grooves, cracks, flow patterns and scale pits.
From a purely mechanical point of view, surface defects are always notches. When the component is loaded, these lead to excessive stress and consequently to damage
surface roughness Surface roughness measures the geometric irregularities of a workpiece surface, caused by the manufacturing process or other influences.
Various roughness parameters can be taken from this surface profile. These are the mean roughness value Ra, the roughness depth Rz, the maximum roughness depth Rt and the mean smoothing depth Rp.
tempering Tempering refers to a process from heat treatment. A material is heated in order to specifically influence the material properties. It is used in particular to reduce tension.
tensile strength Tensile strength measures the maximum mechanical tensile stress that the material can withstand and is only one of several strength parameters.
It is usually calculated from the results of a tensile test, specifically as the quotient of the maximum tensile force achieved and the original cross-section of the standardized tensile test: Rm = FZ / A0
yield point When its yield point is reached, the previously elastic behavior of a material changes into plastic behavior.
From this point on, the material is irreversibly deformed.

The yield point Re is reached when a noticeable elongation occurs with constant or decreasing force. It is subdivided into the upper yield point ReH (stress peak before the force drops for the first time) and the lower yield point ReL (lowest stress within the yield point range).