Welding stress control in high-strength steel components using adapted heat control concepts

Schroepfer, Dirk; Kromm, Arne; Schaupp, Thomas; Kannengießer, Thomas

doi:10.1007/s40194-018-00691-z

Cited by 13 publications

(8 citation statements)

References 19 publications

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“…The weld metal consists of a mixture of bainitic and martensitic phase at the determined t 8/5 -cooling times of 7 to 8 s [50]. The distinction between martensite and bainite in the CGHAZ of the used material is very difficult.…”

Section: Weld Microstructure and Cracks In Implant Specimensmentioning

confidence: 99%

Hydrogen-assisted cracking in GMA welding of high-strength structural steels using the modified spray arc process

et al. 2020

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High-strength structural steels are used in machine, steel, and crane construction with yield strength up to 960 MPa. However, welding of these steels requires profound knowledge of three factors in terms of avoidance of hydrogen-assisted cracking (HAC): the interaction of microstructure, local stress/strain, and local hydrogen concentration. In addition to the three main factors, the used arc process is also important for the performance of the welded joint. In the past, the conventional transitional arc process (Conv. A) was mainly used for welding of high-strength steel grades. In the past decade, the so-called modified spray arc process (Mod. SA) has been increasingly used for welding production. This modified process enables reduced seam opening angles with increased deposition rates compared with the Conv. A. Economic benefits of using this arc type are a reduction of necessary weld beads and required filler material. In the present study, the susceptibility to HAC in the heat-affected zone (HAZ) of the high-strength structural steel S960QL was investigated with the externally loaded implant test. For that purpose, both Conv. A and Mod. SA were used with same heat input at different deposition rates. Both conducted test series showed same embrittlement index “EI” of 0.21 at diffusible hydrogen concentrations of 1.3 to 1.6 ml/100 g of arc weld metal. The fracture occurred in the HAZ or in the weld metal (WM). However, the test series with Mod. SA showed a significant extension of the time to failure of several hours compared with tests carried out with Conv. A.

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Section: Weld Microstructure and Cracks In Implant Specimensmentioning

confidence: 99%

Hydrogen-assisted cracking in GMA welding of high-strength structural steels using the modified spray arc process

et al. 2020

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“…Due to the rather low heat dissipation into the component, especially at higher layer numbers, the cooling time could only be adjusted to a small extent by varying the interlayer temperature at a constant heat input. It should be mentioned that this was in strong contrast to the effect of the interpass temperature on joint welding, which had a significantly higher influence on the cooling rates depending on the plate thickness and applied heat input, with which it also had a considerable interaction [7]. For this purpose, the specimens were divided into four quadrants (Q1 to Q4).…”

Section: Cooling Time During Additive Manufacturingmentioning

confidence: 99%

“…It should be emphasized that the resulting residual stress level on the surface of the top layer was the result of a complex superposition of shrinkage, quenching, and transformation residual stresses according to general concepts, as mentioned above [21]. Other authors investigated these local effects due to high temperature gradients, and found significant influences on the local stress distributions and magnitudes [21], as well as complex interactions with superimposing global welding stresses due to high shrinkage restraints [7]. In comparison to other studies with materials that did not undergo a solidphase transformation during cooling, which influenced the residual stresses; e.g., [8,20], there was an overall change in the stress equilibrium up to an overall reduction in the residual stresses, which can be specifically utilized, or is already systematically exploited by special material developments [22].…”

Section: Residual Stress Analysismentioning

confidence: 99%

“…For welded joints, stress optimization by means of adapted heat-control concepts have already been the subject of research. Schroepfer et al demonstrated the major influence of heat control on the formation of welding residual stresses [7]. It was shown that the interpass temperature in particular affected the global reactions stresses that were superimposed with local welding stresses, and the heat input predominantly influenced the cooling time and weld microstructure.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Heat Control on Properties and Residual Stresses of Additive-Welded High-Strength Steel Components

Scharf-Wildenhain

André

Hensel

et al. 2022

Metals

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Advanced high-performance filler metals for wire arc additive manufacturing (WAAM) exist on the market already. Nevertheless, these high-strength steels are not yet widely used in industrial applications due to limited knowledge of cold-cracking susceptibility, welding residual stresses, and therefore sufficient safety in terms of manufacturing and operation. High residual stresses promote cold-cracking risk, especially in the welding of high-strength steels, as the result of a complex interaction between the applied material, process conditions, and component design. The focus of the present investigation was the determination of the influence of the process parameters on the ∆t8/5 cooling time, mechanical properties, and residual stresses to correlate, for the first time, heat control, cooling conditions, and residual stress for WAAM of high-strength filler materials. This contributed to the knowledge regarding the safe avoidance of cold cracking. In addition to a thermophysical simulation using a dilatometer of different high-strength steels with subsequent tensile testing, reference WAAM specimens (open hollow cuboids) were welded while utilizing a high-strength filler metal (ultimate tensile strength >790 MPa). The heat control was varied by means of the heat input and interlayer temperature such that the ∆t8/5 cooling times corresponded to the recommended processing range (approx. 5 s to 20 s). For the heat input, significant effects were exhibited, in particular on the local residual stresses in the component. Welding with an excessive heat input or deposition rate may lead to low cooling rates, and hence to unfavorable microstructure and component properties, but at the same time, is intended to result in lower tensile residual stress levels. Such complex interactions must ultimately be clarified to provide users with easily applicable processing recommendations and standard specifications for an economical WAAM of high-strength steels. These investigations demonstrated a major influence of the heat input on both the cooling conditions and the residual stresses of components manufactured with WAAM using high-strength filler materials. A higher heat input led to longer cooling times (∆t8/5) and approx. 200 MPa lower residual stresses in the surface of the top layer.

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“…The engineering steels have changed from ordinary carbon steels (e.g., Q345 [8]) to high-strength steels (e.g., Q690 [9] or even Q960 [10]). For the welding of high strength steel, a lot of current research has focused on the process windows of different welding methods [11][12][13][14][15], the influence of alloying elements on weldability [16][17][18], the matching and upgrading of welding wire [19][20][21], and the failure of welded joints [22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Prediction of HAZ Microstructure and Hardness for Q960E Joints Welded by Triple-Wire GMAW Based on Thermal and Numerical Simulation

Wang

Duan³

et al. 2021

Materials

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Since heat affected zone (HAZ) is the weak area of welded joints, this article proposes a method to predict the HAZ microstructure and hardness for the triple-wire gas metal arc welding (GMAW) process of Q960E high strength steel. This method combines welding thermal simulation and numerical simulation. The microstructures and hardness of Q960E steel under different cooling rates were obtained by thermal simulation and presented in a simulated HAZ continuous cooling transformation (SH-CCT) diagram. The cooling rate in HAZ were obtained by numerical simulation with ANSYS software for the triple-wire welding of Q960E thick plates. By comparing the cooling rate with the SH-CCT diagram, the microstructure and hardness of the HAZ coarse-grained region were accurately predicted for multiple heat input conditions. Further, an ideal heat input was chosen by checking the prediction results. This prediction method not only helps us to optimize the welding parameters, but also leads to an overall understanding of the process-microstructure-performance for a complex welding process.

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Welding stress control in high-strength steel components using adapted heat control concepts

Cited by 13 publications

References 19 publications

Hydrogen-assisted cracking in GMA welding of high-strength structural steels using the modified spray arc process

Hydrogen-assisted cracking in GMA welding of high-strength structural steels using the modified spray arc process

Influence of Heat Control on Properties and Residual Stresses of Additive-Welded High-Strength Steel Components

Prediction of HAZ Microstructure and Hardness for Q960E Joints Welded by Triple-Wire GMAW Based on Thermal and Numerical Simulation

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