Effect of Heat Input on Microstructure and Hardness Distribution of Laser Welded Si-Al TRIP-Type Steel

The article presents the possibility of using twin-spot laser welding (i.e. laser welding with focusing a laser beam on two spots) for making overlap joints made of 0.8-1 mm thick HSLA and DP type high strength steel sheets. joints were made using a Yb:YAG disc laser having a maximum power of 12 kW and a welding head by means of which it was possible to focus a laser beam on two spots, 0.6 mm and 1 mm away. The angle between focuses amounted to 0° or 90°, whereas the power distribution was 50%-50%. With settings as presented above it was possible to obtain high-quality overlap joints. The geometrical parameters of the joints were primarily affected by beams positions (in relation to each other) and, to a lesser degree, by the distance between the focuses. It was possible to obtain a 10% hardness reduction in the fusion zone of the DP-HSLA steel joints if the angle between the beams amounted to 90°. The tests also involved microstructural examinations of individual zones of the joints.

Section: Dual Beam Laser Welding Testsmentioning

confidence: 99%

Microstructural Aspects of Twin-Spot Laser Welding of Dp-Hsla Steel Sheet Joints

Stano

Grajcar²,

Wilk³

et al. 2016

“…[1][2][3][4][5]. The reason for this is the ease of shaping, forming and joining of steel blanks [6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Laser Welding of New Grade of Advanced High Strength Steel STRENX 1100 MC

Kurc-Lisiecka¹,

Piwnik²,

Lisiecki³

2017

The article presents results of investigations on autogenous laser welding of new grade STRENX 1100 MC steel. The modern Disk laser was applied for of 5.0 mm thick butt joints welding. The influence of laser welding parameters, mainly the energy input of laser welding on the penetration shape, weld quality, structure and mechanical performance was investigated. It was found that the investigated steel has surprisingly low carbon equivalent CET just 0.328, and also relatively high temperature of martensitic transformation M s at 430.6°C. Despite very rapid cooling times t 8/5 in a range from 0.6 to 1.3 s, thus rapid solidification there was no tendency to cracking of weld metal or HAZ. Significant drop of microhardness in the HAZ resulted in a decrease of tensile strength of joints, compared to the base metal. Impact toughness of test joints was at only 50÷60% of the base metal.

“…For example plasma nitriding requires several hours of processing time [30,31]. Moreover some of the nitriding processes are performed at high temperatures, therefore the bulk of the nitrided sample or a part is exposed to high temperature, so the microstructure and mechanical properties of the bulk material can be also changed and additionally non-uniformity of surface microstructure can occur [32][33]. Additionally, a serious disadvantage of the TiN coatings, reported in the literature, is poor ductility and significant reduction in fatigue wear resistance [1,5,34].…”

Section: Introductionmentioning

confidence: 99%

“…Since the first trials of laser gas nitriding of titanium by Katayama in the eighties of the last century, there have been many studies on the process of laser nitriding of titanium alloys, but the studies were performed under laboratory conditions [5,15,33]. Moreover the technology is not applied in the industry yet.…”

Section: Introductionmentioning

confidence: 99%

Tribological Characteristic of Titanium Alloy Surface Layers Produced by Diode Laser Gas Nitriding

Lisiecki¹,

Piwnik²

2016

In order to improve the tribological properties of titanium alloy Ti6Al4V composite surface layers Ti/TiN were produced during laser surface gas nitriding by means of a novel high power direct diode laser with unique characteristics of the laser beam and a rectangular beam spot. Microstructure, surface topography and microhardness distribution across the surface layers were analyzed. Ball-on-disk tests were performed to evaluate and compare the wear and friction characteristics of surface layers nitrided at different process parameters, base metal of titanium alloy Ti6Al4V and also the commercially pure titanium. Results showed that under dry sliding condition the commercially pure titanium samples have the highest coefficient of friction about 0.45, compared to 0.36 of titanium alloy Ti6Al4V and 0.1-0.13 in a case of the laser gas nitrided surface layers. The volume loss of Ti6Al4V samples under such conditions is twice lower than in a case of pure titanium. On the other hand the composite surface layer characterized by the highest wear resistance showed almost 21 times lower volume loss during the ball-on-disk test, compared to Ti6Al4V samples.