scholarly journals Fatigue Strength Improvement Due to Alloying Steel Weld Toes With WC-Tool Constituent Elements Through Friction Stir Processing

2021 ◽  
Author(s):  
Hajime Yamamoto ◽  
Shodai Koga ◽  
Kazuhiro Ito ◽  
Yoshiki Mikami
Keyword(s):  
Fatigue Strength ◽  
Rotational Speed ◽  
Hsla Steel ◽  
High Strength ◽  
Weld Toes ◽  
Tool Rotational Speed ◽  
Friction Stir ◽  
Steel Layer ◽  
Constituent Elements ◽  
Steel Joints

Abstract Friction stir processing (FSP) enables surface modifications using a rotational tool and can likely be applied as a new post-weld treatment for improving fatigue strength. When applying FSP to high strength materials, tool wear occurring at the interface between the tool tip and the topmost steel layer has been regarded as an unavoidable issue and is related to the tool rotational speed. The present study investigated the relationship between the tool rotational speed and fatigue strength of arc-welded high-strength low-alloy (HSLA) steel joints with weld toes subjected to FSP using a spherical-tip WC tool. FSP was conducted on the weld toe of HSLA steel joints with various tool rotational speeds. Tool wear increased with increase in tool rotational speed, and consequently contents of constituent elements of the WC tool increased in the topmost steel layer of weld toes, leading to large increase of fatigue strength. One reason for the increase with tool rotational speed is significant increase of solid solution hardening due to supersaturated W and C in the topmost steel layer consisting of martensite laths. The hardened topmost steel layer prevented fatigue crack initiation, and the increased fatigue strength depended on the contents of supersaturated W and C.

Microstructure and Mechanical Properties of Friction Stir Welded Joints of Dissimilar AA6061-T6 and AA7075-T6 Aluminium Alloys

2015 ◽  
Vol 787 ◽  
pp. 350-354 ◽  
Author(s):  
V. Saravanan ◽  
Nilotpal Banerjee ◽  
R. Amuthakkannan ◽  
S. Rajakumar
Keyword(s):  
Mechanical Properties ◽  
Welding Speed ◽  
Rotational Speed ◽  
Axial Load ◽  
Microstructural Analysis ◽  
High Strength ◽  
Tool Rotational Speed ◽  
Friction Stir ◽  
Microstructure And Mechanical Properties ◽  
Proper Material

Dissimilar friction stir welding was carried out between AA6061-T6 and AA7075-T6 aluminum alloys. The effect of tool rotational speed and welding speed, on microstructure and mechanical properties were analysed in detail and presented. The tool rotational speed, welding speed, axial load and shoulder diameter to pin diameter (D/d ratio) were the parameters taken into consideration for the study. It was concluded that the tensile strength and hardness value gradually increased with the increase in tool rotational speed and decreased with the further increase in tool rotational speed. The microstructural analysis was carried out for the high strength specimen at various zones. Fine grain size and proper material mixing were observed in the stir zone. Fractographic image of the fractured surface for the high strength joint was presented and discussed. The joint fabricated with tool rotational speed 1000 RPM, welding speed 25 mm/min, axial load 6 kN and D/d ratio 3 exhibited superior mechanical properties when compared to all other joints.

Study on Dissimilar Butt Joining of Aluminum Alloy, AA5052 and High Strength Low Alloy Steel through a Modified FSW Process

2015 ◽  
Vol 830-831 ◽  
pp. 278-281 ◽  
Author(s):  
K.K. Ramachandran ◽  
N. Murugan ◽  
S. Shashi Kumar
Keyword(s):  
Aluminum Alloy ◽  
Rotational Speed ◽  
Joint Strength ◽  
Hsla Steel ◽  
High Strength ◽  
Joint Interface ◽  
Interface Microstructure ◽  
Low Alloy Steel ◽  
Tool Rotational Speed ◽  
Peak Value

In the preset investigation, aluminum alloy, AA5052 and HSLA steel are successfully butt welded using a modified FSW process wherein the work pieces submerged in a liquid medium are stirred by the FSW tool. The trials are conducted by varying the tool rotational speed from 400 rpm to 900 rpm while keeping the other parameters constant. The welded joints are tested for ultimate tensile strength (UTS) and the joint interface microstructure is analyzed using SEM and EDS. The results show that when compared to the normal FSW process, the peak value of UTS is marginally low but the range of tool rotational speed that could produce defect free joints with good joint strength is almost doubled in the modified FSW process.

scholarly journals Fatigue Performance of Thin Laser Butt Welds in HSLA Steel

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1499
Author(s):  
Patricio G. Riofrío ◽  
Fernando Antunes ◽  
José Ferreira ◽  
António Castanhola Batista ◽  
Carlos Capela
Keyword(s):  
Fatigue Strength ◽  
Fatigue Behavior ◽  
Hsla Steel ◽  
High Strength ◽  
Butt Joints ◽  
Factors Affecting ◽  
Weld Profile ◽  
The Relationship ◽  
Good Agreement ◽  
Significant Factors

This work is focused on understanding the significant factors affecting the fatigue strength of laser-welded butt joints in thin high-strength low-alloy (HSLA) steel. The effects of the weld profile, imperfections, hardness, and residual stresses were considered to explain the results found in the S-N curves of four welded series. The results showed acceptable fatigue strength although the welded series presented multiple-imperfections. The analysis of fatigue behavior at low stress levels through the stress-concentrating effect explained the influence of each factor on the S-N curves of the welded series. The fatigue limits of the welded series predicted through the stress-concentrating effect and by the relationship proposed by Murakami showed good agreement with the experimental results.

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