Schaeffler Diagram for Standard Analysis

The Schaeffler diagram is a materials engineering diagram that makes the microstructure of steels visible based on their chemical composition. For standard analysis it is used to classify materials in the diagram and compare them with known material groups. This allows checking whether an analysis lies within the expected range of the standard composition or deviates from it.

The Schaeffler diagram works on two axes: the chromium equivalent on the x-axis and the nickel equivalent on the y-axis. Both equivalents are calculated from the chemical composition of a steel and plotted as a point in the diagram. The position shows which microstructure zone (austenite, ferrite, martensite or mixed microstructure) the material falls in, and whether it corresponds to the expected standard analysis.

capilla supports the application of the Schaeffler diagram and its practical implementation in industrial welding processes.

In standard analysis the Schaeffler diagram is used to verify the materials engineering classification of a steel. The chemical composition is transferred into the diagram and compared with the standard range. This shows whether the actual analysis lies within the expected range or whether deviations from the standard composition exist. This is relevant for materials testing, classification into material groups and assessing further processing.

A standard analysis is the chemical composition of a material as defined in standards, described by the permissible ranges of individual alloying elements. It defines what proportions of chromium, nickel, carbon, manganese and other elements a steel must have in order to correspond to a specific material class. The standard analysis is the reference against which an actual analysis is measured.

Chromium and nickel equivalents are the central characteristic values used to represent the standard analysis in the Schaeffler diagram. The chromium equivalent combines ferrite-forming elements such as chromium, molybdenum, silicon and niobium; the nickel equivalent combines austenite-forming elements such as nickel, carbon, manganese and nitrogen. Both values together determine the position of the standard analysis in the diagram and thus the materials classification.

The microstructure in the weld metal is determined via the calculated chromium and nickel equivalents and the position of the standard analysis in the Schaeffler diagram. Depending on the position, the weld metal lies in the austenite, ferrite, martensite or a mixed microstructure zone. This classification helps predict the behaviour of the weld metal, for example with regard to crack resistance, hardness or processing characteristics.

The Schaeffler diagram shows four main microstructure zones in standard analysis: austenite, ferrite, martensite and mixed microstructures such as austenite-ferrite or austenite-martensite. Each zone represents a typical material behaviour. Austenite is tough and corrosion-resistant, ferrite is soft and magnetic, martensite is hard and brittle. The position of the standard analysis in the diagram shows which microstructure fractions are to be expected in the weld metal.

The standard analysis in the Schaeffler diagram is relevant whenever a materials analysis needs to be verified, a classification into material groups is required or the further processing of a material needs to be assessed. Particularly when welding unknown materials, when mixing different materials or for overlay welding, the position of the standard analysis in the diagram is decisive for the correct choice of filler material and process.

The actual analysis is compared with the standard analysis by calculating the chromium and nickel equivalents from both and plotting them in the Schaeffler diagram. The position of the actual analysis and the corresponding range of the standard analysis are visualised in the diagram. This allows deviations to be identified directly and the materials classification to be verified.

The Schaeffler diagram calculator takes the chemical composition of the actual analysis and the range of the standard analysis as input. On this basis, chromium and nickel equivalents are automatically calculated and plotted in the Schaeffler diagram. The position of the actual analysis and the corresponding standard analysis range are visualised, so that deviations and the materials classification are immediately apparent.