SSAB (Sweden)

This study compares the role of microstructure on post-punching fatigue properties in three advanced high-strength steels (AHSSs) with a high-strength low-alloy (HSLA) steel commonly used in heavy-duty truck chassis. Microstructure characterization, tensile testing, high cycle fatigue (HCF) testing, fatigue crack growth rate (FCGR) testing, and neutron residual stress measurements are conducted. Punching significantly alters the microstructure, causing microstructure refinement, sub-grain formation, defect creation, tensile residual stresses, and a work-hardened shear-affected zone (SAZ) around, and a rough fracture zone, inside the punched hole. At 10 5 cycles, the HCF performance is primarily governed by the fatigue crack growth resistance of the as-rolled microstructure, with minimal sensitivity to punching. However, near the fatigue limit, post-punching fatigue failure is strongly related to strain localization when significant strength difference exists between microconstituents (e.g., martensite and ferrite). Strain localization also promotes sub-grain formation, reducing the local threshold stress intensity factor range (ΔK th ), thus facilitating fatigue crack initiation. In microstructures with smaller strength differences (e.g., ferrite and bainite), sub-grains, together with surface roughness and residual stress, contribute significantly to the post-punching fatigue limit reduction. These findings provide insights into mechanisms of punching-induced fatigue performance degradation, offering potential strategies to optimize fatigue performance of AHSS for new applications. • Post-punching HCF performance around 10 5 cycles is controlled by FCGR behavior. • Post-punching fatigue limit is greatly influenced by punching-induced changes. • Large strength differences between constituents can govern post-punching fatigue crack initiation. • Reduced fatigue limit correlates to strain localization and sub-grain formation.

Abstract Novel generations of shipbuilding steels have outstanding toughness due to the improved steel producing processes. Their microstructure mainly consists of ferrite and bainite, whilst the presence of acicular ferrite has a role in high impact energy of the welded joint. This research aims to analyze the effect of multipass welding on weld characteristics of S500 shipbuilding steel. A Gleeble 3500 simulator machine is used to produce the welding thermal cycles by the Rykalin-3D model on 70 x 10 x 10 mm samples manufactured in transversal direction from a submerged arc welded joint of 16 mm plate. For the simulation of the coarse-grained zone forming in the weld metal (CGHAZ-W) 1350°C and for the intercritical zone (ICHAZ-W) 815°C were selected, while the combination of these peak temperatures was applied for the intercritically reheated coarse-grained zone (ICCGHAZ-W). The examined t8/5 interval was 5…30 s. The weld properties were examined by microstructural examination, hardness test, and instrumented Charpy V-notch impact toughness test. The impact energy values of subzones were below the unaffected weld metal. Longer cooling time resulted in lower impact energy in ICHAZ-W. However, this tendency was not observed in CGHAZ-W. ICHAZ-W and ICCGHAZ-W resulted the lowest impact toughness, which was indicated by the large instable crack propagation.

Hardening of carbon steel products by austenitization and immersion in a quenching medium is a widely used heat treatment to obtain a hard and strong martensitic structure. To avoid the undesired consequences, such as residual stresses or insufficient hardening depth, the cooling rates must be accurately measured and controlled. This can be achieved using the impinging water jet quenching technique. The aim of this work is to perform hardening of four low‐alloyed 70 mm cylindrical carbon steel bars, using impinging water jet quenching technique with different jet flow rates, and to analyze its effect on thermal evolution and residual stresses. The temperature evolution during quenching experiments is recorded and used as input to a comprehensive quenching model to predict phase transformations, final hardness, and residual stresses of cylindrical bars. All four quenching experiments result in a fully hardened martensitic state. Furthermore, a decrease in jets’ flow rate, within a certain interval, results in different thermal histories and in lower compressive residual stresses on the surface. The results from quenching simulations show promising hardness, microstructure, and residual stress predictions that are validated by hardness measurements, optical microscopy, and residual stress analysis using X‐Ray diffraction method.

The decreased fatigue capacity of welded components with increasing plate thickness, known as the size effect, is a well-known phenomenon in most fatigue design standards. The size effect links directly to the probabilistic nature of fatigue failure, where the extent of stress concentrations and stress gradients through the thickness governs the fatigue capacity of the joint. Fatigue design standards and recommendations address the thickness effect by modifying the S-N curve for joints thicker than the reference thickness value; however, the increase in fatigue strength due to the thinness effect is commonly not considered. The probabilistic nature of fatigue failure for welded joints is investigated in the current study using the weakest link modelling approach based on the stress distribution in the welded joint. The modelling approach is evaluated with the effective notch stress method and evaluated against fatigue test data for non-load-carrying welded joints found in the literature. The differences and similarities between the probabilistic and effective notch stress methods give a good insight into how the fatigue strength of welded joints is correlated to the size effect.

This article focuses on composer Wilhelm Stenhammar’s relationship with the nascent Swedish folk music movement, namely the individuals, networks and organizations committed to preserving folk music in Sweden. The matter is briefly discussed by Bo Wallner in his biography of Stenhammar (1991), and his conclusion is that Stenhammar is ‘standing beside’ this movement. Unlike several contemporary colleagues he did not, for example, actively participate in the production of written records and, according to Wallner, seems to have lacked personal contacts with ‘experts’ on the subject. The present article is based on new or previously overlooked facts leading to a modification of Wallner’s conclusion. In the 1910s, Wilhelm Stenhammar was one of those who actively got involved in the issue of the possibilities of the phonograph in the documentation of folk music. He was in personal contact with Yngve Laurell, assistant at The Swedish Museum of Natural History, who had been educated at the Berliner Phonogramm-Archiv. By engaging donors Stenhammar greatly contributed to Laurell being able to carry out phonograph recordings of Swedish folk music during several years. In 1914 Stenhammar was also one of eleven prominent figures in Swedish cultural life who signed an appeal for ‘a phonogram archive for folk music’ with the Berliner Phonogramm-Archiv as a likely model. Placing Wilhelm Stenhammar beside the contemporary folk music movement without contacts with experts in the field is therefore wrong. By making Laurell’s recording work financially possible, his involvement also gained historical significance for the genre. Keywords: Wilhelm Stenhammar, folk music, folk music movement, phonograph, Yngve Laurell, Berliner Phonogramm-Archiv.

ABSTRACT Although older consumers constitute a growing consumer segment with substantial buying power, not much is known about their satisfaction with retail stores and its antecedents. This study examines how having in-store, face-to-face service encounters with store personnel affects the store satisfaction of older consumers, focusing on the moderating role of consumer age and the mediating role of positive emotions. An empirical study demonstrates positive effects of service encounters with store employees on the store satisfaction and positive emotions of older consumers. Consumer age moderates these effects, so that there are no similar positive effects of in-store service encounters on store satisfaction or positive emotions for the younger consumers. Positive emotions also mediate the effects of in-store service encounters on store satisfaction for the older consumers, but not for the younger consumers.

The paper summarizes the creation of a robust online grain size gauge for a hot strip mill. A method and algorithm for calculating the grain size from the measured ultrasonic attenuation is presented. This new method is self-calibrating, does not rely on a geometrical reference sample and can cope with the effects of diffraction on the attenuation. The model is based on 52 quenched samples measured with more than 23,000 laser ultrasonics shots and has a correlation coefficient R2 of 0.8. Typical online laser ultrasonic measurements from the hot strip mill and the calculated grain size versus length are presented for a couple of steel strips.

Substitution of coal in coking coal blend with bio-coal is a potential way to reduce fossil CO2 emissions from iron and steelmaking. The current study aims to explore possible means to counteract negative influence from bio-coal in cokemaking. Washing and kaolin coating of bio-coals were conducted to remove or bind part of the compounds in the bio-coal ash that catalyzes the gasification of coke with CO2. To further explore how the increase in coke reactivity is related to more reactive carbon in bio-coal or catalytic oxides in bio-coal ash, ash was produced from a corresponding amount of bio-coal and added to the coking coal blend for carbonization. The reaction behavior of coals and bio-coals under carbonization conditions was studied in a thermogravimetric analyzer equipped with a mass spectrometer during carbonization. The impact of the bio-coal addition on the fluidity of the coking coal blend was studied in optical dilatometer tests for coking coal blends with and without the addition of bio-coal or bio-coal ash. The result shows that the washing of bio-coal will result in lower or even negative dilatation. The washing of bio-coals containing a higher amount of catalytic components will reduce the negative effect on bio-coke reactivity, especially with acetic acid washing when the start of gasification temperature is less lowered. The addition of bio-coal coated with 5% kaolin do not significantly lower the dilatation-relative reference coking coal blend. The reactivity of bio-cokes containing bio-coal coated with kaolin-containing potassium oxide was higher in comparison to bio-coke containing the original bio-coal. The addition of ash from 5% of torrefied bio-coals has a moderate effect on lowering the start of gasification temperature, which indicates that the reactive carbon originating from bio-coal has a larger impact.

The characteristics of nonmetallic inclusions (NMIs) in low‐alloyed steel samples taken during ladle treatment before and after Ca treatment are evaluated using the pulse distribution analysis optical emission spectroscopy (PDA/OES) method, INCA‐Feature investigations of inclusions on a polished surface of steel samples, and 3D investigations of NMIs after electrolytic extraction (EE) of steel samples. The investigation results of NMIs using the different methods were compared. The PDA/OES results show a clear tendency of a change in the average composition and quantity of NMIs during ladle treatment, which correlates well with the results obtained from the other two methods. Overall, it is found that the application of the PDA/OES method is appropriate to enable a fast online evaluation of inclusion compositions and their behaviors during steelmaking. This, in turn, provides the means for establishing an online control and correction of technological operations of the ladle treatment to implement necessary modification of NMIs to improve the cleanliness of steels and avoid clogging problems during casting.