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Jachym R.,Instytut Spawalnictwa Institute of Welding | Lomozik M.,Instytut Spawalnictwa Institute of Welding | Kwiecinski K.,Instytut Spawalnictwa Institute of Welding | Urzynicok M.,ZELKOT Boiler Elements Factory | And 2 more authors.
ASM Proceedings of the International Conference: Trends in Welding Research | Year: 2013

Dynamic development of steels used in power engineering industry for the production of boilers characterised by supercritical parameters poses new welding challenges. The introduction of new combinations of alloying elements aimed at obtaining the best possible mechanical properties, including creep resistance, affects the weldability of new steels. Each of the latter must undergo many tests, particularly as regards bending and welding, in order to enable the development of technologies ensuring failure-free production and assembly of boiler systems. Martensitic steels containing 9% Cr, used in the manufacturing of steam superheaters, are characterised by good creep resistance and, at the same time, low oxidation resistance at a temperature in excess of 600°C. In turn, steels with a 12% Cr content are characterised by significantly higher oxidation resistance, but accompanied by lower strength at higher temperatures, which translates to their limited application in the production of boilers operating at the highest parameters. The niche between the aforesaid steels is perfectly filled by austenitic steels, the creep resistance and oxidation resistance of which are unquestionable. This article presents experience gained while welding similar joints of steel TEMPALOY A-3 and dissimilar joints of steels TEMPALOY A-3 and T91, with the use of EPRI87. The tests involving the said steel grades belong to the very few carried out in the world. Copyright © 2013 ASM International® All rights reserved.

Weglowski M.S.,Instytut Spawalnictwa Institute of Welding | Zeman M.,Instytut Spawalnictwa Institute of Welding | Lomozik M.,Instytut Spawalnictwa Institute of Welding
Materials Science Forum | Year: 2013

In the present study, the investigation of weldability of new ultra-high strength - Weldox 1300 steel has been presented. The thermal simulated samples were used to investigate the effect of welding cooling time t8/5 on the microstructure and mechanical properties of the heat affected zone (HAZ). In the frame of these investigation the microstructure was studied by the light (LM) and transmission electron microscopies (TEM). It has been shown that the microstructure of the Weldox 1300 steel is composed of tempered martensite, and inside the laths the minor precipitations mainly V(CN) and molybdenum carbide Mo2C were observed. Mechanical properties of parent material were analysed by the tensile, impact and hardness tests. In details the influence of cooling time in the range of 2.5 - 300 s on hardness, impact toughness and microstructure of simulated HAZ was studied by using welding thermal simulation test. The results show that the impact toughness and hardness decrease with the increase of t8/5 under the condition of a single thermal cycle in simulated HAZ. The continuous cooling transformation diagrams (CCT-W for welding conditions) of Weldox 1300 steel for welding purposes was also elaborated. The steel Weldox 1300 for cooling time in the range of 2.5 - 4 s showed martensite microstructure, for time from 4 s to 60 s - mixture of martensite and bainite, and for longer cooling time mixture of ferrite, bainite and martensite. The results indicated that the weldability of Weldox 1300 steel is limited and to avoid the cold cracking the preheating procedure or medium net linear heat input should be used. © (2013) Trans Tech Publications, Switzerland.

Lomozik M.,Instytut Spawalnictwa Institute of Welding | Zeman M.,Instytut Spawalnictwa Institute of Welding | Jachym R.,Instytut Spawalnictwa Institute of Welding
Kovove Materialy | Year: 2012

The article describes the cracking of argon-welded TIG-welded circumferential butt joints of light-wall tubes made of steel X10CrMoVNb9-1 (T91), using filler metal C9 MV-IG. Fragments of welded joints and weld deposits underwent macro- and microscopic metallographic examination involving light microscopy. The investigation also involved tests of mechanical properties, impact energy and hardness, as well as chemical composition analyses. Structural tests of the areas containing cracks revealed the presence of high-temperature ferrite delta (ferrite Δ). It was determined that the cracks in the welds of circumferential butt joints were caused by too high yield point and tensile strength of the weld metal not subjected to heat treatment (if compared with the corresponding properties of steel T91). The publication also provides technological recommendations specifying how to prevent the formation of cracks in such types of welded joints.

In this paper, results of vibration welding of glass fibre-reinforced nylon 66 are presented. The hot air blower was used for preheating of the welded surfaces before the welding process. The aim of the research was determination of the influence of the thermal conditions of vibration welding process on the quality of joints, including weld microstructure, the content of the crystal phase, orientation of the glass fibres in the weld and the tensile strength. Influence of the welding conditions on the weld microstructure and the orientation of the glass fibres was determined during the light microscopic examinations as well as in the scanning electron microscopic examinations. A melting temperature and the content of the crystal phase of welds were tested using differential scanning calorimetry (DSC). Fitting of the mathematical function describing penetration curve was performed, and calculations of the heat power were made. Comparison of results of vibration welding of nylon composite conducted with and without preheating was carried out. Results indicate that the use of preheating during vibration welding process eliminates the solid-state friction in the welding process and leads to the significant improvement of the welds quality at the shorter weld time. © 2014, The Author(s).

Winiowski A.,Instytut Spawalnictwa Institute of Welding | Rozanski M.,Instytut Spawalnictwa Institute of Welding
Archives of Metallurgy and Materials | Year: 2014

Alloys based on the Fe3Al intermetallic phase belong to a new generation of metallic materials intended for operation at higher temperatures and having properties something between those of metals and ceramic materials. They are characterised by relatively high oxidation resistance, high corrosion resistance, high-temperature creep resistance, high electrical resistivity, high abrasion resistance as well as resistance to erosion and cavitation. Although the material costs of these alloys are relatively low, they belong to materials which are very difficult to join by means of welding methods. For this reason, joining such materials remains an important and current research and technological problem. One of the methods used for joining such materials is brazing. This work shows the results of technological tests concerned with vacuum brazing an alloy based on the Fe3Al (Fe86Al14) phase using silver (Ag72Cu28) and copper-nickel (Cu90Ni10, Cu95Ni5) filler metals as well as presents the results of tests on the mechanical and structural properties of obtained joints. © 2014, Committee of Metallurgy. All rights reserved.

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