Welding Metallurgy of

Fracture and fatigue crack growth analyses on a weld-repaired railway rail

...................................................................................................... 60 KOKKUVÕTE ................................................................................................... 62 APPENDICES .................................................................................................... 65 Curriculum vitae ................................................................................................. 67 Elulookirjeldus ................................................................................................... 69

Steel Selection Considerations for Hot-Dip Galvanizing

This master thesis aims to study hybrid joints of polyetherimide (PEI) and aluminum 6082-T6 produced by Friction-based Injection Clinching Joining (FICJ). The influences of the process parameters in the frictional heat and polymer degradation were analyzed through a half factorial design. The degradation of PEI was evaluated by size exclusion chromatography (SEC), differential scanning calorimetry (DSC) and infrared spectroscopy (FTIR). The effect of degradation in the joint microstructure and mechanical properties was also analyzed. The macro and microstructural characteristics were evaluated by optical microscopy and Vickers hardness. The static mechanical properties were determined by lap shear testing and cross tensile testing. It has been shown that the F-ICJ causes degradation through multiple chains scissions. Additionally, a thermomechanically affected zone, with lower hardness, and defects such as pores and weld lines are formed. The mechanical performance, mainly in cross tensile testing, is negatively affected by degradation and presence of defects. These results contribute to the optimization and application of F-ICJ to join hybrid structures. Key-words: Friction joining, injection-based clinching joining, F-ICJ, hybrid joints, polyetherimide, PEI, degradation

Universidade federal de são carlos centro de ciências exatas e de tecnologia programa de pós-graduação em ciência e

This study examined the effects of substrate preheating for the hardfacing of cold-press dies using the high-speed tool steel AISI M4. The preheating of the substrate is a widely used technique for reducing the degree of thermal deformation and preventing crack formation. We investigated the changes in the metallurgical and mechanical properties of the high-speed tool steel M4 deposited on an AISI D2 substrate with changes in the substrate preheating temperature. Five preheating temperatures (100-500 °C; interval of 100 °C) were selected, and the changes in the temperature of the substrate during deposition were observed. As the preheating temperature of the substrate was increased, the temperature gradient between the melting layer and the substrate decreased; this prevented the formation of internal cracks, owing to thermal stress relief. Field-emission scanning electron microscopy showed that a dendritic structure was formed at the interface between the deposited layer and the substrate while a cellular microstructure was formed in the deposited layer. As the preheating temperature was increased, the sizes of the cells and precipitated carbides also increased. Furthermore, the hardness increased slightly while the strength and toughness decreased. Moreover, the tensile and impact properties deteriorated rapidly at excessively high preheating temperatures (greater than 500 °C). The results of this study can be used as preheating criteria for achieving the desired mechanical properties during the hardfacing of dies and molds.

Effects of substrate preheating during direct energy deposition on microstructure, hardness, tensile strength, and notch toughness

https://scholarsmine.mst.edu/cgi/viewcontent.cgi?article=3092&context=matsci_eng_facwork

Effect of Zinc Galvanization on the Microstructure and Fracture Behavior of Low and Medium Carbon Structural Steels

https://file.scirp.org/pdf/ENG_2013110615435220.pdf

Effect of Preheating Temperature on the Mechanical and Fracture Properties of Welded Pearlitic Rail Steels

https://file.scirp.org/pdf/ENG_2015122114015308.pdf

Effect of Environmental Conditions on Tin (Sn) Whisker Growth

The metallurgy of ASTM A615/A615M Gr. 60 steels made from three different chemistries was studied to suggest an economically advantageous route to produce a steel grade that saves the extra cost of alloying elements. Metallographic examinations, along with microhardness and XRD studies, were performed to rate the steel chemistries based on their superheats. This study of the steel grades revealed that producing steel for requisite standards like ASTM 615/A615M Grade 60 may not be dependent on starting superheat but on the chemistry and rolling process. Study of the three chemistries A, B and C indicated that the standards were met in all 3 chemistries; however, sample A had the lowest cost chemistry and therefore is a suggested route for this product. 1. Introduction. ASTM A615/A615M Grade 60 standard calls for a minimum 60 Ksi (420MPa) yield strength with no upper limit even on tensile strength. The standard only specifies that phosphorus (P) be no more than 0.06%. The resulting plain carbon steel is expected to have basic ferrite - pearlite microstructure with minimum grain size ASTM 5. Because every steel mill is different and processes vary, some steel mills use some microalloying to achieve fine grain size in pursuit of the aim microstructure. This process of compositional and process variations can produce yield strengths typically in the range of 350 to 700 MPa (50 - 100 Ksi). Microalloying, which enhances physical properties through ferritic grain refinement, is often supplemented by precipitation and or dislocation strengthening. Hall-Petch type of strengthening is determined to suggest that a decrease of ferritic grain size from ASTM 6 - 8 to ASTM 12 - 13 is accompanied by an increase of 30 Ksi (210 MPa) in yield strength. Admittedly the other good effect of fine grains besides strengthening is good ductility or toughness. Two common microalloying elements V and Nb are used in industry to achieve this goal and several authors (1-6) have studied their use. It is known that the behavior of individual micro alloying elements classifies them as mildly carbide forming or strongly carbide forming. The two micro alloying elements (V and Nb) used in this study do qualify as strong carbide formers. They therefore stabilize the α phase. This essentially means that they reduce the γ phase field. Any of the elements in solid solution in α strengthen the ferrite matrix in steel. These elements differ in their contribution to hardening and the extent to which they reduce plasticity as they add a certain increment to strength. Furthermore, compared to other microalloying elements like Nb and Ti, vanadium exhibits essential differences. The Swedish Institute of Metals Research (6) found that the solubility of vanadium carbonitrides, in particular, is much larger and the solubility of vanadium's nitride is about two orders of magnitude smaller than its carbide, contrary to Nb but similar to Ti. Vanadium has higher solubility in austenite than niobium, and its carbonitrides (V(C,N)) dissolve more easily prior to hot rolling than NbC. Consequently, vanadium is an excellent choice for strong and easily controllable precipitation strengthening, but it is expensive.

https://hal.archives-ouvertes.fr/hal-01302025/document

Kaushal R. Prayakarao

Papers

Effect of Zinc Galvanization on the Microstructure and Fracture Behavior of Low and Medium Carbon Structural Steels

Effect of Preheating Temperature on the Mechanical and Fracture Properties of Welded Pearlitic Rail Steels

Effect of Environmental Conditions on Tin (Sn) Whisker Growth

Producing A615 / A615M High Strength Construction Re-Bars Without Use of Microalloys: Part 2