K. Granat

Application of microwaves for innovative hardening of environment-friendly water-glass moulding sands used in manufacture of cast-steel castings

The paper presents examination results on possible implementing an innovative microwave technology for manufacture of high-quality, economic cores of water-glass moulding sands. A special attention was paid to improving technological properties of the examined moulding sands and in particular of their strength and knocking-out properties by selecting proper parameters of the hardening process. In addition, some benefits are indicated, resulting from applying such an innovative and environment-friendly solution effectively replacing traditional and energy-consuming processes of preparing moulding cores.

Possibilities of laser-beam joining cemented carbides to steel

Welded joints of cemented carbides with steel are commonly present in tool production, mainly those used in the machining and mining industry. The article presents possibilities of joining cemented carbides H10S and G10 with steel C45 using laser radiation. These are the first innovative experiments carried out in Poland. Joints between cemented carbides and steel were made both directly and using spacers between the materials to be joined, which were made of copper, triple-layer solder Ag49/Cu and nickel. The joining trials were carried out at the Laser Technology Centre of the Institute of welding in Gliwice. A Triumpf disc laser (λ = 1030 nm) Tru-Disc 12002 with output power of 12 kW was used for this purpose. The laser beam was focused mostly on the steel surface to avoid direct interaction between the laser beam and the structure of cemented carbides. The assessment of joints of cemented carbides with steel C45 was conducted on the basis of metallographic evaluation, EDX analyses and microhardness measurements.

Soldering of aluminium with copper

Soldering of aluminium with copper becomes more significant, because of relatively low process temperature of about 400–450°C. It is applied not only in electrotechnical industry, in joining Al–Cu conductors, but also in cooling and air-conditioning equipment and in solar construction of collectors (Winiowski A. Lutowanie twarde aluminium i jegostopów – nowe trendy technologiczne, Biuletyn Instytutu Spawalnictwa, nr 6/2000, Fontargen GmbH. Löten in der Kälte- und Klimatechnik, Eisenberg. 2001 and Fontargen GmbH. Aluminium-Löten. Eisenberg 2003). In this paper, problems concerning Al–Cu soldering are presented. For soldering, zinc solders with the addition of 2, 4, and 15 wt% Al have been used. Results of wettability and spread factor measurements of zinc solders on aluminium and copper surface, as well as metallography, microhardness, and shearing tests of Al–Cu joints are presented. Effects of copper pipes with aluminium plate soldering with application of flux coating solders are also described.

Effect of Temperature on Chromite-Based Moulding Sands Bonded with Sodium Silicate

In the paper, a research on effects of baking temperature on chromite sand base of moulding sands bonded with sodium silicate is presented. Pure chromite sand and its chromite-based moulding sand prepared with use of sodium silicate were subjected to heating within 100 to 1200 °C. After cooling-down, changes of base grains under thermal action were determined. Chromite moulding sand was prepared with use of 0.5 wt% of domestic made, unmodified sodium silicate (water-glass) grade 145. After baking at elevated temperatures, creation of rough layer was observed on grain surfaces, of both pure chromite sand and that used as base of a moulding sand. Changes of sand grains were evaluated by scanning microscopy and EDS analyses. It was found that changes on grain surfaces are of laminar nature. The observed layer is composed of iron oxide (II) that is one of main structural components of chromite sand. In order to identify changes in internal structure of chromite sand grains, polished sections were prepared of moulding sand hardened with microwaves and baked at elevated temperatures. Microscopic observations revealed changes in grains structure in form of characteristically crystallised acicular particles with limited magnesium content, intersecting at various angles. EDS analysis showed that these particles are composed mostly of chromium oxide (III) and iron oxide (II). The temperature above that the a.m. changes are observed in both chromite-based moulding sand and in pure chromite sand. The observed phenomena were linked with hardness values and mass of this sand.

Powder solders for hard soldering of aluminium and its alloys

Nowadays, aluminium and its alloys are successfully joined using various welding methods in many fields of technology. These include hard soldering, thanks to which bonding may be obtained which meets especially high requirements. Application of aluminium and its alloys in soldered joints is common in the construction of heat exchangers, e.g. heating, cooling and air-conditioning systems, as well as in electric machines and connections for conducting electric current. In the last 20 years, hard soldering has become especially important in the construction of aluminium air-conditioning systems for the automotive industry and air conditioners for building units. Aluminium flame soldering should be performed with carefully selected soldering technology. Depending on whether this is manual or mechanized soldering, the choice of filler should be considered, i.e. fluxes, controlled atmospheres or solders. Thanks to their great running quality, silumin-based solders containing 5–12% by weight silicon are most frequently used for hard soldering of aluminium and its alloys. Among these, ordinary solders A1Si12, AlSi10 and AlSi7,5 are most often used in practice. This paper presents examples of flame soldering using powder solders. These were manufactured from a Nocolok brand made of AlSi12 alloy and non-corrosive flux with a thickness of 0.3mm. Due to flux activity temperatures ranging from 565 to 5728C, close to the solder melting temperature, it is not recommended to use these materials separately for manual soldering. However, great results are obtainable using these materials under oven soldering conditions, in a controlled atmosphere, where the soldering temperature may be precisely specified. Joining of AlSi12 solder with Nocolok flux in the form of a powder wire facilitates manual flame soldering, even under difficult assembly conditions.