MICROSTRUCTURE AND MECHANICAL PROPERTIES OF STEELS FOR SHAPED CHARGE LINERS AND PRELIMINARY ASSESSMENT OF THE EFFECTIVENESS OF EXPERIMENTAL SHAPED CHARGES INTENDED FOR USE IN THE MINING INDUSTRY

The paper presents the results of investigation of the microstructure and mechanical properties of Fe-based materials designed for the manufacture of semi-spherical liners for experimental shaped charges. The tests were carried out on material samples taken from two semi-finished products, i.e. a rod for the manufacture of charge liners with a diameter of 50 mm using machining, and sheets for the manufacture of liners with a diameter of 100 mm using cold drawing. Microstructure examination was also carried out on a test specimen obtained using the additive method (3D-WAAM), made of low-carbon unalloyed steel wire. Firing tests on concrete blocks were carried out in order to quantify the effects of drilling at the Experimental Mine Barbara. The scope of the tests consisted of firing at cylindrical concrete blocks using projectiles containing 50 mm diameter liners made of Fe-based alloys. Based on the results of the laboratory material, two experimental steel grades were selected for further testing. Plates made of the selected steels will be used to manufacture charge liners with a diameter of 100 mm.

The separation of ε- and γ’-phases in the plasma nitrided layer by colour etching techniques

In this research, various etching reagents were tested on a quenched and tempered 42CrMo4 steel and an untreated C45E unalloyed steel sample, whichwere plasmanitrided for 4 h at 490 °C with 75% N2–25% H2 gas mixture. The aim is to find a reagent suitable for revealing and separating the two ε- and γ’-phases in the nitrided layer. Previously, the compound layer’s composition could only be identified by X-ray diffraction (XRD), a costly, time-consuming and not easily accessible process. Therefore, finding an alternative could be crucial for small businesses. Nital, Picral, Villela, and Oberhoffer’s reagents were investigated in the experiments. Scanning electron microscope (SEM) was used to observe the nitrided layer, and it was analysed by XRD to detect the formed phases and electron dispersive X-ray spectroscopy (EDS) was used to analyse the elemental composition. Nital is the most common used etchant in the industry, but Oberhofferwas found to be an excellent etchant to separate the two phases in a dual phases nitrided layer.

The Use of Arc Welding Processes in the Additive Manufacturing of Metallic Products

The article presents examples of additive manufactured products obtained using MIG /MAG welding processes (13). The research-related tests revealed that it is possible to make products of unalloyed steels having the structure similar to castings subjected to heat treatment. Products made of maraging steel require homogenising (heat treatment). It is possible to produce bimetallic products, e.g. unalloyed steel-bronze.

Influence of Heat Input and Welding Position on Geometrical Properties of GMAW Fillet Welds of Unalloyed Steel

This paper presents principal influences of heat input and welding position on geometrical properties of fillet welds for conventional and pulsed GMAW of unalloyed steel. We took into consideration geometrical properties such as fillet weld size, penetration, dilution and reinforcement. All presented influences are represented by fitting curves, based on simple linear regression of experimental data provided by visual and macro-section examination.

The Role of the Material of Active Screen During the Plasma Nitriding Process

In this research the effect of the active screen’s material was investigated. 42CrMo4 steel was plasma nitrided with unalloyed steel, titanium and nickel active screen at 490 and 510 °C for 4h in 75 % N2 + 25 % H2 gas mixture. Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS) were used for the characterisation of the surface properties. Iron-nitride was not formed on the surface with nickel screen. The evaluation of examination results showed that most of the detected nitrogen was molecular (N2) in the formed layer.