| 1. |
- Fahlström, Karl, et al.
(författare)
-
Distortion Analysis in Laser Welding of Ultra High Strength Steel
- 2014
-
Ingår i: Proceedings of the 6th International Swedish Production Symposium 2014. - 9789198097412 ; , s. 1-9
-
Konferensbidrag (refereegranskat)abstract
- Due to increased demands on reduced weight in automotive industries, the use of ultra high strength steels (UHSS) has increased. When laser welding UHSS sheets, heating and cooling of the material will cause geometrical distortions and may cause low joint quality. 700 mm long U-beam structures of 1 mm thick boron steel simulating structural pillars in body-in-white constructions have been welded along the flanges with different welding speeds to investigate distortions and weld quality. The results show that final distortions appear in the range of 0-8 mm. FE simulation methods have also been presented which generally predict the distribution of welding distortions.
|
|
| 2. |
- Harati, Ebrahim, et al.
(författare)
-
The measurement of weld toe radius using three non-destructive techniques
- 2014
-
Ingår i: Proceedings of The 6<sup>th</sup> International Swedish Production Symposium 201416-18 September 2014. - 9789198097412 ; , s. 1-8
-
Konferensbidrag (refereegranskat)abstract
- The three non-destructive methods Weld Impression Analysis, Laser Scanning Profiling and Structured Light Projection were employed to measure the weld toe radius of fillet welds. All three methods could be used succesfully but results are dependent on evaluation procedure. The results show that the weld toe geometry cannot be considered uniform and varies along the weld. It was also found that the measured weld toe radii do not vary significantly with minor variations ofthe surface profile orientation.
|
|
| 3. |
- Karlsson, Leif, 1952-, et al.
(författare)
-
Efficient welding of high strength steel
- 2014
-
Ingår i: Proceedings of the 6th International Swedish Production Symposium 2014. - 9789198097412 ; , s. 1-8
-
Konferensbidrag (refereegranskat)abstract
- Producing welds with properties matching those of the steel is a challenge at high strength levels. The present study investigated how cooling rates and dilution affects strength and toughness when welding steels with yield strengths of 777 MPa and 1193 MPa. Overmatching weld metal strength was achieved for the less strong steel and weld strengths >1000 MPa were recorded for the stronger steel. Fracture in transverse tensile testing was always located in base material or HAZ. Low dilution, rapid cooling and single pass welding contributed to higher strength. Impact toughness was higher for lower strength and low dilution.
|
|
| 4. |
|
|
| 5. |
- Karlsson, Leif, 1952-, et al.
(författare)
-
Orientation relationships of intragranular austenite in duplex stainless steel weld metals
- 2014
-
Ingår i: Science and technology of welding and joining. - 1362-1718 .- 1743-2936. ; 19:4, s. 318-323
-
Tidskriftsartikel (refereegranskat)abstract
- Formation and characteristics of fine intragranular austenite were studied for low energy input duplex stainless steel welds. Microstructures were largely ferritic with some allotriomorphic grain boundary austenite, Widmanstätten type austenite, fine intragranular austenite and nitrides. Electron backscattered diffraction analysis revealed that grain boundary austenite had a random orientation relationship (OR) with one of the adjacent ferrite grains and was close to Kurdjumov-Sachs (KS) with the other, whereas Widmanstätten austenite always showed an OR near KS. The finest intragranular austenite was mainly randomly oriented, whereas coarser austenite more often was close to KS. It is argued that the OR of intragranular austenite with the ferritic matrix is governed by a combination of composition, determining driving force for nucleation at temperature, cooling rate and the availability of nitrides acting as nucleation sites. A random OR is most likely for higher cooling rates and compositions promoting nucleation at lower temperatures. © 2014 Institute of Materials, Minerals and Mining.
|
|
| 6. |
|
|
| 7. |
- Mráz, Lubos, et al.
(författare)
-
Residual stress distribution measurement by neutron diffraction of the single pass fillet steel welds
- 2014
-
Ingår i: 52nd International Scientific Conference on Experimental Stress Analysis (EAN 2014). - : Czech Society for Mechanics ( CSM ). - 9781632668226
-
Konferensbidrag (refereegranskat)abstract
- In this contribution the results of residual strain/stress measurements performed on several single pass fillet steel welds which were carried out at different welding conditions, namely, with different filler materials are presented.
|
|
| 8. |
- Mraz, Lubos, et al.
(författare)
-
Residual stress distributions at high strength steel welds prepared by low transformation temperature (LTT) and conventional welding consumables
- 2014
-
Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 777, s. 40-45
-
Tidskriftsartikel (refereegranskat)abstract
- Residual stress distributions in fillet welds in 8 mm 900 MPa steel have been mapped perpendicular and parallel to the weld line and also through the thickness in the vicinity of weld toe position. Measurements were carried out on four welds when two of them were performed with conventional and two with the so called LTT (low transformation temperature) filler materials. Both neutron and X-ray diffractions were used for determination of the residual stress distribution. Fatigue properties have also been evaluated for all test welds. Neutron diffraction measurements showed that the stress profiles perpendicular to the weld toe qualitatively did not depend on filler material type although the absolute stress levels differed. Trends were similar for positions 2, 4 and 6 millimetres below the surface for all three stress components; σx (direction perpendicular to the weld), σy (parallel to the weld) and σz (through the thickness). X-ray diffraction showed difference in residual stress level at the weld toe. Lower residual stress levels have been identified for LTT filler material when compared to the conventional consumable compositions. The effect of residual stress is discussed in relation to fatigue properties of all four welds. Remarkable higher fatigue strength has been measured for welds prepared by the LTT filler materials. © (2014) Trans Tech Publications, Switzerland.
|
|
| 9. |
- Valiente Bermejo, María Asunción, et al.
(författare)
-
Influence of low energy laser welding on solidification and microstructure of austenitic stainless steel welds
- 2013
-
Ingår i: 14th NOLAMP Conference. - Luleå : Luleå University of Technology. - 9789174396881 - 9789174396898 ; , s. 3-14
-
Konferensbidrag (refereegranskat)abstract
- Primary austenitic solidification is related to increased hot cracking susceptibility in welding of austenitic stainless steels. It is also recognised that high cooling rates and rapid solidification conditions, like those achieved in laser beam welding (LBW), increase the stability of austenite versus ferrite as the primary solidification phase. Knowledge about the solidification mode under LBW conditions is therefore of utmost importance. A series of austenitic stainless steel alloys were prepared using an electric arc furnace and cooled at a rate of 10 ºC/s. The overall alloying composition was kept constant at [Cr eq+Nieq] = 40 wt% while changing the Cr eq/Nieq ratio from 1.52 to 1.84. These alloys were then laser welded using a continuous wave ytterbium fibre laser at two different energy input levels. Cooling rates were experimentally determined to be in the range of 10 3 ºC/s to 104 ºC/s and the values were confirmed by computational modelling. The compositional border between primary austenitic and primary ferritic solidification was found to shift to higher Cr eq/Nieq values at higher cooling rates. However, all the alloys showed coexistence of regions of primary austenitic and primary ferritic solidification for both laser settings although ustenite tended to more abundant at higher cooling rates. Austenite content and refinement of microstructure is discussed in terms of effects of cooling rate on solidification behaviour and solid state transformations.
|
|
| 10. |
- Valiente Bermejo, María Asunción, et al.
(författare)
-
Optimising Quality and Productivity in Welding of Duplex and Superduplex Stainless Steels
- 2014
-
Ingår i: Proceedings of the 6th International Swedish Production Symposium 2014. - 9789198097412 ; , s. 1-7
-
Konferensbidrag (refereegranskat)abstract
- The aim of this work was to study the influence of shielding gases and welding positions on properties of duplex and superduplex stainless steel circumferential pipe welds. Corrosion resistance, microstructural features and weld defects were assessed and related to the welding procedures. Horizontal and vertical upward welding positions produced high quality welds. However, welding in the overhead position resulted in less good results in terms of porosity and corrosion resistance. Shielding gases containing 30% helium showed best results, whilst using a mixture Ar+2%CO2 resulted in undercuts and porosity in all welding positions.
|
|
