Abstract
Properties of low-alloy boron-containing steels Brinar 400 and Brinar 500 in as-delivered and normalized conditions are considered. Charpy tests carried out within temperature ranges of ductile-to-brittle transition were followed by fractographic analysis. The tests were carried out on specimens with their axes parallel and perpendicular to hot-working direction, at −40°C, −20°C, 0°C, and +20°C. The determined impact properties of Brinar steels were complemented with fractographic analysis performed with use of a scanning electron microscope. It was found that temperatures of ductile-brittle transition were significantly different for the materials in as-delivered and normalized conditions. In addition the tensile tests were carried out, determining basic strength properties of the analyzed materials.
Highlights
The examinations were performed on selected grades of low-alloy martensitic steels containing boron, with higher resistance to abrasive wear
When 35 J/cm2 is accepted as the brittleness criterion corresponding to 50-% occurrence of plastic and brittle fractures, it can be said that both analyzed steels meet this criterion in the entire range of testing temperatures; see Figure 7
Important differences between impact strength values in longitudinal and transverse directions were found for this steel
Summary
The examinations were performed on selected grades of low-alloy martensitic steels containing boron, with higher resistance to abrasive wear. It is worth stressing that these properties are reached, even if chemical composition basically does not include additive elements (except boron) in the amounts commonly accepted as alloying percentages This is why, from the viewpoint of chemical composition, properties of these steels should not be significantly different from those of unalloyed low- and medium-carbon steels. Presence of boron and selected microadditions, combined with complex operations of thermomechanical treatment, made it possible to obtain highly favorable mechanical properties, unattainable in unalloyed carbon steels These materials should be treated as a separate material group subjected to separate research procedures. In order to obtain high mechanical parameters and abrasion resistance, such typical heat treatment is quenching and low tempering It happens that these steels are delivered by the manufacturers in different conditions, sometimes not including hardening, with a suggestion that heat treatment is to be carried out by the customer. A significant part of energy is absorbed during cracking as surface energy [6]
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