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Suitability analysis of thermally hardened S620Q steel sheets used for welded constructions working in lowered temperatures

100%

Cicholska M.

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tom Vol. 17, No. 4

103-108

EN

S620Q steel sheets 12 mm thick that were heat treated were subjected to research. The sheets weldability was examined during semi-automatic welding by MAG method, at the welding conditions usually applied in industry for welding normalized sheets of this steel. The achievement of metallically continuous joints was confirmed by X-ray examination, the correctness of making test joints was confirmed by the measurement of transverse warp and edges of sample sections. Moreover the following tests were carried out: static tensile tests, technological bending tests and impact tests on the samples with V-notch cut in positions S, P, C2 and C5. The joints microstructure was observed in the weld axis, in SWC and in native materials with the use of Neophot-2 optical microscope. Steel microstructure was classified as low-carbon, tempered martensite of layered construction. The bend tests were carried out by means of bending arbour 36mm in diameter. The impact energy values for test temperatures -60°C, -40°C and -20°C marked in the drawings are the mean values of breaking three samples at a given test temperature. The places ofnotches cuts applied on welded joints samples are required by Det Norske Veritas regulations for welded joints. Mechanical properties ofS620Q steel were given as reference.

2

The influence of welding on the hardness and weldability of thermally hardened S620Q steel sheets

100%

Cicholska M.

Journal of KONES

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2012

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tom Vol. 19, No. 4

127-130

EN

The thermally hardened 12 mm sheets of S620Q steel underwent research. The sheets weldability was examined during semi-automatic welding by MAG method, at the welding conditions usually applied in industry for welding normalized sheets of this steel. The technology of welding was presented. The achievement of metallically continuous joints was confirmed by X-ray examination. For the purpose of usefulness assessment, samples were taken from test joints then the joints hardness distribution measurements were performed. The microstructure was examined and the static tensile tests as well as technological bend tests were carried out. Hardness measurements were performed in three measurement lines for each joint according to PN-EN 1043-1:2000 requirements. Joints microstructures were examined in the joints axis, in SWC and in native materials. Steel microstructures were classified as low carbon tempered martensite of layered construction. Mean values of the selected joints strengths were also presented. The tensile tests values of native materials of metallurgic certificates were given for the sake of comparison. The research results presented in the paper made it possible to determine the weldability of S620Q steel.

3

The influence of treating welded joints edges on the strength and fatigue of S640Q steel

100%

Cicholska M.

|

tom Vol. 24, No. 2

59--64

EN

Weldable steels of high strength were discussed. The factors influencing the achievement of low grain structure that ensures high strength of these steels was explained. Traditional and modern methods of producing high strength steel were shown. The scheme of production line was shown, the line which is used to manufacture steel of high strength in thermomechanical way. The methods of achieving strength to fatigue used for welded joints were presented. The factors influencing the increase of strength to fatigue of welded joints were elaborated. The thermally hardened steel sheets of high strength weldable S640Q steel underwent research. Basic mechanical properties of this steel were indicated. The results of static tensile test and technological bend test were given. Then the sheets were welded by semiautomatic MAG method. The examinations of welds quality were conducted and their usefulness for further tests was stated. Mechanical properties of welded joints were determined. The mechanical properties of native material and welded joints were compared. The microstructure of welded joints in the weld axis, in heat influence zone as well as in native material was examined. Fatigue tests in a non-symmetrical cycle of lengthening – compressing for the welded joints were carried out. The computational strength to fatigue was determined and compared with fatigue strength of welded joints. Tests results were elaborated by the statistical analysis of linear regression. After conducting fatigue tests, the Wöhler diagrams were made. Afterwards, the joints welded with TIG method, were penetrated without adding filler metal. The results were presented for the fatigue tests as well as the Wohler graph for welded joints after penetration of the joints edges with TIG method without adding filler metal. The results were compared.

4

The influence of the shape of weld nobs on the fatigue strength of S540Q steel

100%

Cicholska M.

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tom Vol. 23, No. 4

63--69

EN

The development of weldable steels was discussed together with the methods of obtaining them. The influence of these methods on steel properties was explained. Research was performed on quenched weldable S540Q steel of high strength. Basic mechanical properties of this steel were determined. The results of a static tensile test and technological bending test were given. Next, steel sheets were welded by semi-automatic MAG method. The welds quality was examined and their future suitability was stated. Mechanical properties of the joints welded of this steel were determined. Mechanical properties of native material and welded joints were compared. Joints microstructure was examined in the weld axis, in the heat influence zone and in the native material. Fatigue tests were conducted in the cycle of nonsymmetrical tension – compression of welded joints. The analytical fatigue strength was obtained and it was compared with fatigue strength of welded joints. Tests results were elaborated with the static analysis of linear regression. Wohler diagrams were made after conducting fatigue tests. Finally, weldable joints were melted by TIG method without adding filler metal. The angle and radius of welds nobs entrance into the native material was measured. The increase of fatigue strength is related to the decrease of geometric notch on the edges of weld nobs.

5

Suitability analysis of thermally hardened S540Q steel sheets for welded constructions working in low temperatures

100%

Cicholska M.

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2013

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tom Vol. 20, No. 3

105--109

EN

The conventional heat treatment is being replaced by thermal-plastic treatment. The process of steel hardening is carried out on quenching press with a double-sided water spray at the temperatures ranging from 600 to 700°C. The steel hardening process is conducted at the temperatures of 600-700°C with cooling in the air. After this, thermal hardening the steel sheets obtain the structure of a layered tempered matrensite with carbide and cyanide disperse separations The thermally hardened S540Q steel sheets 12 mm thick underwent examinations. The welding technology was presented. The sheets were welded semi automatically by means of MAG method. The usual welding conditions normally applied in industry were used after steel standardisations. The achievement of joints metallically continuous was confirmed by X-ray tests. The static tensile test was conducted to assess the applicability of this steel. The average values of the welded joints resistance to tensile strength were given. After conducting technological bend, test good ductility was noted. Steel microstructure was defined as low carbon tempered matrensite of layered construction. Microstructure observation was carried out in the joint axis, in heat affected zone and in native material. Hardness measurements were performed according to PN-EN 1043-1:2000 requirements. Impact test was conducted on the samples with a V cut notch at the temperatures of -20, -40, -60 Celsius degrees.