The Low-Cycle Fatigue Strength of Laser-Welded Ultra-High-Strength Steel

2011 ◽  
Vol 473 ◽  
pp. 281-289 ◽  
Author(s):  
Markku Keskitalo ◽  
Kari Mäntyjärvi ◽  
Toni Kiuru
Keyword(s):  
Fatigue Strength ◽  
Energy Input ◽  
Weld Seam ◽  
Low Cycle Fatigue ◽  
High Surface ◽  
Base Material ◽  
High Strength ◽  
Welding Parameters ◽  
Light Weight ◽  
Design Strength

The UUltra -high -strength (UHS) steels are used in booms, transport vechicles and other light weight structures. It is well -known that it is possible to achieve a strong weld statically, as the base material, by using laser welding as a weld method [1]. The design strength of the light weight structure is often rather high. In the case of booms and transport vechilevehicles, there can be very high dynamic forces in the structure. Therefore it is necessary to study how much fatigue stress the weld seam can resist and at the same time find the optimal welding parameters. The 4 mm bainitic-martensitic UHS steel was welded with laser without filler material to lasercut seam edges by using different weld parameters. Argon gas was blown by pipe onr coaxial nozzle near the key hole and through a 60 mm gas nozzle after the keyhole. Also, the root side of the weld was shielded with argon. The welds were tested by using the bending fatigue test. The test stresses were 800 MPa and 700 MPa. The fatigue strength results showed that with the laser welded seams, the number of cycles wereas about three times lower than with the base material. The fatigue strength was slightly better in welds which were welded with lower energy input. In the case of the weld seam which was welded with lowest energy input by using 300 mm optics, there was some incomplete penetration due to tooexcessively high surface roughness ofat the weld seam edges.

Impact of Welding Parameters on Weld Seam Properties of Seamless X80 Linepipe Steel Grade

2014 ◽  
Author(s):  
Claas Bruns ◽  
Jörg Wiebe ◽  
Dorothee Niklasch ◽  
Denise Mahn ◽  
Tanja Schmidt
Keyword(s):  
Weld Seam ◽  
Mechanical Test ◽  
Base Material ◽  
Welding Process ◽  
Charpy Impact ◽  
High Strength ◽  
Impact Testing ◽  
Welding Parameters ◽  
Test Results ◽  
Linepipe Steel

The challenging exploration conditions appearing in ultra deep offshore projects promoted the development of high strength linepipe steel grades with yield strength of 80 ksi and higher in recent years. With increasing strength more attention has to be paid to welding procedures to realise the required mechanical properties of the weld seam. The combination of demanding toughness requirements at low temperatures and adequate corrosion resistance of welded joints is a key for complex deep offshore riser and linepipe applications. The welding process was optimised by Vallourec with respect to heat input and preheating temperature for joining seamless quenched and tempered pipes in grade X80. A root welding strategy has been developed particularly with regards to sour service applications. Extensive mechanical test results including Charpy impact testing, hardness, CTOD and SSC testing will be presented. In addition Gleeble trials were carried out using different thermal cycles to simulate multilayer welding. The aim was to improve the understanding of the base material behaviour in the heat affected zone (HAZ) during welding. The microstructure was characterized by LOM, SEM and furthermore hardness and Charpy impact tests were executed. Based on the gathered knowledge and test results welding recommendations and welding strategies for high strength steel X80 seamless line pipes are deduced.

Influence of the base material on the mechanical behaviors of polycrystal-like meta-crystals

2021 ◽  
pp. 2150004
Author(s):  
J. Lertthanasarn ◽  
C. Liu ◽  
M.-S. Pham
Keyword(s):  
Synergistic Effects ◽  
High Surface ◽  
Base Material ◽  
High Strength ◽  
Yield Stability ◽  
Yield Behavior ◽  
Specific Strength ◽  
Base Materials ◽  
Lattice Materials ◽  
Strength And Stiffness

Architected lattice metamaterials offer extraordinary specific strength and stiffness that can be tailored through the architecture. Meta-crystals mimic crystalline strengthening features in crystalline alloys to obtain high strength and improved post-yield stability of lattice materials. This study investigates synergistic effects of the base material’s intrinsic crystalline microstructure and architected polycrystal-like architecture on the mechanical behavior of architected metamaterials. Four different polygrain-like meta-crystals were fabricated from 316L, Inconel 718 (IN718) and Ti6Al4V via laser powder bed fusion (L-PBF). While the elastic modulus of the meta-crystals did not vary significantly with the base material or the number of meta-grains, the strength of the meta-crystals showed strong increasing correlation with reducing the size of meta-grains. The differences between meta-crystals made by the three alloys were the most substantial in the post-yield behavior, where the 316L meta-crystals were the most stable while Ti6Al4V meta-crystals were the most erratic. The differences in the post-yield behavior were attributed to the base material’s ductility and intrinsic work-hardening. For all base materials, increasing the number of meta-grains improved the post-yield stability of meta-crystals. The tolerance to the processing defects also differed with the base material. Detrimental defects such as the high surface roughness on the downskin of the struts or the large, irregularly shaped pores near the surface of the struts led to early strut fracture in Ti6Al4V meta-crystals. In contrast, ductile IN718 was able to tolerate such defects, enabling the most significant synergistic strengthening across lengthscales to achieve architected materials of low relative density, but with a very high strength and an excellent energy absorption.

PERSPECTIVE WELDING TECHNOLOGIES OF ALUMINUM-LITHIUM ALLOY V-1469 APPLIED TO FUSELAGE PANELS

2020 ◽  
pp. 35-46
Author(s):  
M.D. Panteleev ◽  
◽  
A.V. Sviridov ◽  
A.A. Skupov ◽  
N.S. Odintsov ◽  
...  
Keyword(s):  
Friction Stir Welding ◽  
Laser Welding ◽  
Low Cycle Fatigue ◽  
Base Material ◽  
High Strength ◽  
Friction Stir ◽  
Lithium Alloy ◽  
Aluminum Lithium Alloy ◽  
Aluminum Lithium ◽  
Welding Processes

In this work, we investigated the technological features of promising technologies for laser welding and friction stir welding of high-strength aluminum-lithium alloy V-1469. The modes of laser welding and friction stir welding have been carried out. In this article, we showed the perspective welding methods provide high values of ductility and impact toughness, while the strength of welded joints is not less than 0,8 of the strength of the base material and values of low cycle fatigue is not less than 110•103 cycles. The results allows to propose laser welding and friction stir welding processes as an alternative to riveted joint for aluminum-lithium alloy V-1469 as applied to the elements of the fuselage.

scholarly journals The structure and properties of laser seam stepper system (LSS) welded the low alloy high strength steel DOCOL 1200M with martensitic structure

2018 ◽  
Vol 2 (1) ◽  
Author(s):  
Jacek Górka 1 ◽  
Andrzej Ozgowicz 2
Keyword(s):  
Welded Joints ◽  
Base Material ◽  
High Strength ◽  
Hardness Measurement ◽  
Welding Parameters ◽  
Martensitic Structure ◽  
Structure And Properties ◽  
Destructive Testing ◽  
Metallographic Examination ◽  
Actual Length

This paper will present the influence of joining process parameters on the structure and properties of overlapped welded joints of 1.8 mm DOCOL 1200M steel. The obtained welded joints were subjected to micro- and macroscopic metallographic examination and hardness measurement. The visual inspections and non-destructive testing made it possible to develop the field of welding parameters to allow obtaining full penetration joints (depending on requirements) or partial penetration joints. For present welding parameters, i.e. feed rate and weld length, which are constant, the actual length of weld is determined by welding frequency. In each case, the microscopic examinations revealed martensitic structure in the weld area, and with the increase in linear welding energy the size of martensite needles became larger, especially in relation to the base material. In HAZ, the martensitic structure is tempered. It has been shown that with appropriately selected parameters the Laser SEAM Stepper method is suitable for welding the DOCOL 1200M steel. With the increase in welding power, the penetration depth increases.

The Effect of Prior Surface Roughness on Fatigue Life of Nitrided Specimens

2020 ◽  
Vol 405 ◽  
pp. 271-276
Author(s):  
Marta Kianicová ◽  
Pavel Šandera ◽  
Jana Horníková ◽  
Daniel Kottfer ◽  
Jaroslav Pokluda
Keyword(s):  
Surface Roughness ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Surface Defects ◽  
Low Cycle Fatigue ◽  
High Strength ◽  
Case Hardening ◽  
Hardening Treatment ◽  
Initiation Stage ◽  
Almost All

The effect of surface roughness of virgin specimens (prior roughness) made of low-alloyed high strength steel on their fatigue life after the case-hardening treatment was studied by rotating bending tests of virgin and nitrided samples. In a whole range of S-N curves, the fatigue strength of virgin samples after lathe-turning machining (high roughness) was naturally much higher than that of samples after grinding (low roughness). As expected, the fatigue strength of nitrided specimens was higher than that of virgin samples when averaged through the whole fatigue life range. When distinguishing the rough and smooth nitrided samples, the low-cycle fatigue strength of rough samples revealed to be lower than that of the smooth ones and vice a versa in the high-cycle region. This could be explained by the fact that, in the low cycle region, the cracks in the rough samples nucleated from deep surface defects while, in the smooth specimens, they nucleated from shallow defects (or as fish eyes) which prolonged their initiation stage. Almost all cracks in the high cycle region initiated as fish-eyes but the extent of nitrided layers in the rough specimens was slightly higher than that in the smooth specimens. Therefore, the fish-eye centers were shifted further to the interior of the rough specimens which increased their fatigue life.

scholarly journals Beneficial use of hyperbaric process conditions for welding of aluminium and copper alloys

2021 ◽  
Author(s):  
K. Treutler ◽  
S. Brechelt ◽  
H. Wiche ◽  
V. Wesling
Keyword(s):  
Energy Density ◽  
Penetration Depth ◽  
Weld Seam ◽  
Ambient Pressure ◽  
Copper Alloys ◽  
Base Material ◽  
Welding Parameters ◽  
Process Conditions ◽  
Novel Approach ◽  
Core Parameter

AbstractThe joining of components with as few weld layers as possible is an important aspect of weld seam design due to the resulting reduced manufacturing effort and reduced influence of thermal cycles on the base material as well as reduced distortion. For materials with good thermal conductivity, this is not easily possible. The energy density of the arc has been found to be the core parameter for determining the penetration. In the present work, it is shown how the use of a hyperbaric process environment (2 to 16 bar) allows an increase of the energy density of the arc and thus an increase of the penetration depth for selected aluminium and copper alloys. Furthermore, the effects of this novel approach on weld metal metallurgy are presented. It is shown that the penetration depth can be doubled by increasing the ambient pressure. Furthermore, a statistical model for the prediction of the penetration depth depending on the welding parameters will be presented.

Feasibility study of welding dissimilar Advanced and Ultra High Strength Steels

2020 ◽  
Vol 59 (1) ◽  
pp. 54-66
Author(s):  
Francois Njock Bayock ◽  
Paul Kah ◽  
Antti Salminen ◽  
Mvola Belinga ◽  
Xiaochen Yang
Keyword(s):  
Heat Input ◽  
High Strength Steel ◽  
Gas Metal Arc Welding ◽  
Base Material ◽  
Welding Process ◽  
High Strength Steels ◽  
High Strength ◽  
Hardness Test ◽  
Welding Parameter ◽  
Welding Parameters

AbstractThis study concerns the weldability of dissimilar Ultra high-strength steel (UHSS) and advanced high-strength steel (AHSS), which is used in the modern machine industry. The materials offered superior strength as well as relatively low weight, which reduces microstructure contamination during a live cycle. The choice of the welding process base of the base material (BM) and welding parameters is essential to improve the weld joint quality. S700MC/S960QC was welded using a gas metal arc welding (GMAW) process and overmatched filler wire, which was performed using three heat input (7, 10, and 15 kJ/cm). The weld samples were characterized by a Vickers-hardness test, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The test reveals a decrease of softening areas in the HAZ and the formation of the stable formation of Bainite-Ferrite for S700MC and Bainite-martensite for S960QC when the heat input of 10 kJ/cm is used. It is recommended to use the GMAW process and Laser welding (Laser beam-MIG), with an optimal welding parameter, which will be achieved a high quality of manufacturing products.

Influence of Friction Stir Welding Parameters on the Mechanical Properties of EN AW-7075 Weld Joints

2016 ◽  
Vol 835 ◽  
pp. 210-215
Author(s):  
Máté Nagy ◽  
Mária Behúlová
Keyword(s):  
Mechanical Properties ◽  
Friction Stir Welding ◽  
Ultimate Strength ◽  
Base Material ◽  
High Strength ◽  
Welding Parameters ◽  
Micro Hardness ◽  
Friction Stir ◽  
Weld Joints ◽  
Welding Processes

The paper deals with the friction stir welding (FSW) of the high strength EN AW 7075-T651 aluminium alloy with the aim to analyze the influence of welding parameters on the mechanical properties of Al-weld joints. FSW represents relatively novel solid-state technology of material joining which can be successfully applied for welding of several metallic alloys including the high-strength aluminium alloys that are hard to weld by conventional fusion welding processes. In cooperation with VÚZ - PI SR Bratislava, nine experimental weld joints of samples with dimensions of 300 × 150 × 10 mm were prepared using the welding machine of the FSW-LM-060 type and different parameters of welding – the welding speed from 60 to 120 mm/min and the tool rotation rate from 600 to 1000 rpm in clockwise direction. The quality of weld joints was evaluated by static tensile tests and micro-hardness measurements. According to obtained results of tensile testing, the average values of ultimate strength of weld joints are by 32.2 % lower comparing with the ultimate strength of the base material. On the other hand, the ductility increased by 7.2 %. The highest micro-hardness of weld joints at the level of 129 HV was measured in thermo-mechanically affected zone on the retreating side.

Sign in / Sign up

Export Citation Format

Share Document