Materials Science

The relevant properties of a material can be further tailored to its intended application through additional processing steps.

One of the most important procedures is heat treatment in the form of aging: the steel is exposed to a precise temperature for an exact period. This accelerates diffusion—the equalization of concentration differences within the metal—and thereby enhances its crystalline structure. Through the formation of precipitates, a single-phase solid solution transforms into a two-phase alloy.

Depending on how long the steel is subjected to a given temperature, the balance between the material's strength and ductility changes. Here, strength refers to the material's resistance to mechanical load before deformation, while ductility is the ability to deform under shear stress before fracturing. Together, they define a material's toughness. Notably, a material cannot simultaneously exhibit high strength and high ductility—these properties are diametrically opposed.

In brief, aging allows for targeted adjustment of a material’s mechanical properties across a broad range.

The standard aging grades for 1.4542 are:

• H900: Maximum strength of Rm from 1310 MPa, but lower ductility (A minimum of 10%). Used for highly stressed components.
• H925: Slightly lower strength values of Rm from 1170 MPa, but higher toughness. A good compromise between strength and ductility.
• H1025: Moderate strength of Rm 1070 MPa with good ductility (A minimum of 12%). Versatile in application.
• H1075: Slightly lower strength values of Rm from 1000 MPa, with greater elongation (A minimum of 13%).
• H1100: Strength values of Rm from 965 MPa, good balance between strength and toughness (A minimum of 14%).
• H1150: Lowest strength values of Rm from 930 MPa, but highest ductility (A minimum of 16%). For components with high toughness requirements.

Reading Tip: Practical Explanation of Hardness, Toughness, Ductility, and Strength

Note: The strength values within each respective aging grade for materials 1.4545 and 1.4548 are identical to material 1.4542.

By the way, material numbers such as 1.4542 or 1.4548 are not assigned arbitrarily but contain a wealth of information. How to read them and what the numbers represent is explained in a dedicated article from our WE Know-How Library. Here’s a brief overview:

• The digit before the decimal point represents the main group of the material; here, 1 stands for steel with Rm < 500 N mm^-2.
• The second and third digits form the grade number, providing additional information about the material itself. 45 indicates stainless steel.
• The final two digits make up the sequential identifier. The larger the number, the more recently the material was developed.