Improving the Abrasion Resistance of Nodular Cast Iron Castings by Remelting Their Surfaces by Laser Beam.

This paper presents the results of research conducted in the field of the technology of surface hardening of castings from unalloyed and low-alloy nodular cast iron using the laser remelting method. The range of studies included macro- and microhardness measurements using Rockwell and Vickers methods as well as metallographic microscopic examinations using a scanning electron microscope. Moreover, abrasive wear resistance tests were performed using the pin-on-disk method in the friction pair of nodular cast iron-SiC abrasive paper and the reciprocating method in the friction pair of nodular cast iron-unalloyed steel. Analysis of the test results shows that the casting surface layer remelting by laser for unalloyed nodular cast iron results in a greater improvement in its resistance to abrasive wear in the metal-mineral system, as compared to low-alloy cast iron. Additionally, carrying out the laser hardening treatment of the surface layer made of the tested grades of nodular cast iron is justified only if the tribological system of the cooperating working parts and allowable dimensional changes during their operation are known.

Influence of Weather Conditions and Mechanical Reclamation on Molding Sand with Alkali-Phenolic Binder for Manganese Cast Steel.

The article presents the results of research on the properties of molding sands in Alphaset technology (alkaline-phenolic). These sands are often used in steel foundries, producing large castings. However, knowledge about them, and especially about the changeability of their properties with the change of environmental conditions (seasons), is still insufficient. Various compositions of molding sand were analyzed based on fresh chromite sand and reclaimed sand. A binder and hardener in various mass ratios were used to prepare the mass. The research methodology included, among others, tests of tensile and bending strength, permeability, abrasion, gas emissivity, and ignition losses. These tests were carried out for summer and winter conditions. The results showed the optimal proportions of resin and hardener, showed the influence of ambient temperature on the properties of the molding sand, and the possible ratio of reclaimed sand in relation to fresh sand. However, you should always remember to verify them under the conditions of a specific foundry.

Repair of a Cracked Historic Maryan Bell by Gas Welding.

In this article, the range of works connected with the repair of a historical Maryan bell from 1639 are presented. The first attempts to repair damaged bells occurred in the 1930s in Poland. However, this process was stopped because of extensive technological difficulties. Welding and soldering-welding were the basic methods. There is one difference between these two methods-connecting surfaces are melted during the welding process but only heated until the melting temperature of the material added to the connection (that is the solder) during the soldering-welding process. It was important to heat the bell to the proper temperature during welding. Uneven heating causes the enlargement of existing cracks or the appearance of new ones, or even the complete destruction of the bell. Nowadays, a method of even heating using a special heating mat has been devised. Thanks to this method it is possible to control the heating and cooling process. The most important task during the whole operation of bell welding was obtaining the original sound. During this research, the chemical composition was examined to prepare a welding rod with a suitable chemical composition. After the repair process, an analysis of the sound of the bell was conducted. It was shown that the repair of bells is possible when correct thermal parameters are used. The most highly recommended technique for repairing bells is gas welding.