ISSN 2300-1674

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No. 02/2012

S. KOWIESKI, Z. MIKNO, A. PIETRAS - Welding of advanced high-strength steels
Resistance spot welding is commonly applied in the production of steel car structures. The article presents processes during the welding of high-strength steel sheets with protective coatings (including recently introduced protective-coated advanced steels with an organic layer). Special attention was given to tests investigating the welding of advanced high-strength TRIP-type steels. These steels, when welded with a simple one-pulse welding programme, are characterised by very high hardness in the welding area, and as a result, undergo a rupture in the trans-crystallisation plane during peel testing. In order to improve the plasticity of a joint, it proved appropriate to apply a two-pulse welding technology while joining such steels. It was ascertained that the use of an appropriately adjusted second current pulse would make it possible to obtain lower metal hardness in a weld nugget. During peel testing, joints welded with the second heating current pulse are destroyed by the complete peeling of a weld nugget.

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D. MIARA, A. PIETRAS - Friction stir welding (FSW) casting aluminium alloys with wrought alloys
Friction stir welding (FSW) is a friction welding technology particularly useful for joining aluminium alloys which are difficult to weld or even unweldable by means of other methods. The study presents selected results of tests of butt welding of casting aluminium alloys and results of tests related to joining casting aluminium alloys and wrought alloys. According to the test results, casting alloys (and casting alloys with wrought alloys) can be joined by means of FSW obtaining relatively high quality of joints within a limited range of welding conditions. The quality of joints depends on applied welding process parameters, i.e. rotational speed of the tool, linear welding rate, forces and torques/moments. The structure of the weld is proper. It is possible to observe small micro-cracks in the weld, particularly in the area of intermetallic phases. The surfaces of the face and root of the weld are free from material discontinuities. During visual inspection, no imperfections such as no joint or porosity were detected.

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M. St. WGLOWSKI - Modern toughened steels - their properties and advantages
The article presents the characteristics of toughened steels, their mechanical properties and production methods. Special emphasis is given to metallurgical purity and the deterioration of plastic properties accompanied by an increase in mechanical properties. The study also emphasises the advantages of using steels characterised by higher mechanical properties and discusses problems occurring during welding very high-strength steels. Special attention is given to cold cracking, welding-induced HAZ softening and failing to obtain a required level of toughness in the weld and HAZ. The article also provides information about criteria related to the selection of filler metals.

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J. CZUCHRYJ, K. HYC - Dye-penetrant method assessment of the size of surface discontinuities in products made of carbon structural steel
Some of the oldest and most common non-destructive tests used in the industrial practice are liquid-penetrant inspections. They enable, however, the detection of surfacing discontinuities only. Nevertheless, the possibility of estimating the size of these discontinuities may be useful in the technical diagnostics of products subject to inspections. This inspired the work aimed to determine the dependence between the size of an indication and the time of its development in the function of the size of a discontinuity. This article contains research results, their analysis and final conclusions.

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No. 01/2012

J. DWORAK - Impact of laser beam shape on YAG pulsed laser welding
The study presents the general characteristic of laser welding with a radiation beam emitted in pulsed mode and explains the characteristics of the energy-related parameters of a pulsed radiation beam. The text indicates the shape of a pulse (specific course of power changes within the duration of a pulse) as one of the parameters of a laser beam influencing the process of welding, particularly of thin precision elements. Examples of penetrations and welded joints were used to illustrate the possibility of changing the shape of a weld and the manner of weld metal crystallisation by applying laser beam pulses of diversified shapes.

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A. SAWICKI - Modified Habedank and TWV hybrid models of the arc with variable length for simulating processes in electrical devices
The paper indicates main difficulties in determination of characteristics and mathematical modelling of the electric arc. Limitations in practical use of the simplified and combined models of discharge with constant plasma column length have been pointed out. New plasma column models with variable arc length have been presented. The models consist of series or parallel connected elements corresponding to the modified Cassie-Berger and Mayr-Kulakov ones.

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E. TURYK, A. YDZIK-BIAEK, M. BORMANN, A. JASTRZBIOWSKI,
M. KOŚCIELNIAK, T. KUZIO, B. CZWRNG - Repair welding of elements of the sign "ARBEIT MACHT FREI" of the main gate to the former German Nazi concentration and extermination camp Auschwitz I
The article presents theft-accompanying damage to the sign "ARBEIT MACHT FREI" and discusses the requirements of the Conservation Section of the Auschwitz-Birkenau State Museum related to the joining of the sign elements and the extent of conservation performed. The study also covers the process and results of the work regarding the technology of the repair welding of the sign carried out at Instytut Spawalnictwa and addresses the issue of welding-related technological supervision.

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A. KISZKA, T. PFEIFER - Variable polarity MAG welding of thin protective-coated steel plates
The study presents results of research on the application and usability of variable polarity MAG welding of thin protective-coated sheets in automotive industry. The research-related process was carried out using OTC Daihen DW 300 and Cloos Qineo Champ welding devices. The study also discusses the influence of EN ratio in the course of current and voltage on the stability of process, quality of joints, and the degree of damage to protective coating.

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M. ST. WGLOWSKI - Testing electromagnetic radiation of welding arc in TIG method from welding process monitoring point of view
The study presents the results of tests of welding arc electromagnetic radiation in TIG method. Within the research it was necessary to carry out an extensive overview of reference publications about arc radiation and applied testing methods. Taking advantage of an arc model in TIG method described in reference publications it was possible to determine a dependence of welding current intensity and welding arc length on the intensity of welding arc visible radiation. The research-related tests made it possible to determine new parameter values in the generalised arc model for a 25-mm range of welding arc length, which resulted in better matching of a model. It was also possible to demonstrate that an increase in welding current intensity for a constant length of a welding arc causes an increase in the intensity of arc visible radiation and that the same effect can be obtained by increasing an arc length at constant welding current intensity. The research also led to a conclusion that the monitoring of welding arc visible radiation in TIG method can be used for controlling an arc length.

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