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In recent years, promising technique of deep cryogenic treatment (DCT) is taking a new step in improving properties of various materials, especially steels. This study is focusing on influence of selected heat treatment process involving deep cryogenic treatment on the microstructure and microstructural evolution of four different steel grades (bearing steel 100Cr6, cold work tool steel X210Cr12, hot work tool steel X38CrMoV5-3 and stainless steel X17CrNi16-2). The study was performed for different heat treatment conditions, focused on effectiveness of DCT when using different austenitizing and tempering temperatures. The evolution of the microstructure was investigated in a sequential manner with various analytical techniques. The study indicates that the microstructure and microstructural evolution and changes are strongly related to the chemical composition of steel and the predefined matrix microstructure. DCT increases precipitation of carbides and induce their more homogenous distribution. The magnitude of increased carbide precipitation after DCT is correlated with the higher carbon content, whereas the content of other alloying elements does not scale with the precipitation behavior. The obtained results indicate that incorporation of DCT with heat treatment with higher austenitizing and lower tempering temperature is the most suitable for improving steels’ properties with DCT, due to the stronger impact of DCT on the carbide precipitation and matrix modification.

Excessive exposure to heat can lead to injuries, illness, and death among mineworkers. The actual cost of heat-related injuries and illnesses is unknown because of underreporting and lack of symptom recognition. Multi-factorial, evidence-based, and field-ready guidelines for identifying–and predicting–physiological markers of heat strain are currently unavailable. The predicted heat strain (PHS) model, is the latest attempt by mining companies to aid in the evaluation and management of occupational heat exposures. The adopted algorithm relies on worksite environmental measurements and an estimate of individual metabolic rate for mine workers to provide an estimate of the workers’ core temperature during a work shift. There are several known limitations of the PHS model, including the assumption that the subject worker is hydrated and fit. A modified PHS model was presented based on eight physical parameters that are measured at different intervals during a work shift; these parameters are air temperature, relative humidity, air velocity, radiation, metabolic rate, acclimatization, clothing insulation and posture. To validate the results, the predictions from the modified PHS model were compared with direct physiological measurements obtained from ingestible pills and heat stress monitors under different environmental and working conditions.

In this research, the microstructure evolution in the machined subsurface is numerically simulated through a developed multi-physics model applied to H13 hot work die steel. The multi-physics model based on dislocation density evolution is utilized to predict the change of grain size through finite element analysis by varying cutting parameters. In spite of the cutting conditions, the simulated grain size on the top-most machined surface is around 330 nm, and the machining-affected depth with refined grain varies in the range of 25–45 μm. In addition, the appeared periodical fluctuation of dislocation density and grain size in a wavy configuration induced by the generated serrated chip segments is revealed. The efficacy of the proposed finite element model is verified and the probable mechanism of grain refinement is demonstrated with the assistance of TEM observation, which in turn promotes the in-depth understanding of microstructure evolution during metal cutting.

The failure mechanisms under thermal-mechanical conditions have always been a critical issue in hot work steels. However, previous studies mainly focused on the mechanical properties of hot work materials, while the underlying deformation mechanism remains largely unclear. Here, we investigate the crack morphology and microstructure evolution mechanism near the fracture surfaces of 4Cr5MoSiV1 hot work die steels subjected to the uniaxial tension at 580 °C. An evident deformation band was observed consisting of refined α-Fe grains with a width of about 100nm along both sides of the intergranular fracture surface. Additionally, characteristic slip band rings formed frequently, presumably due to the grain rotation near the crack. Finally, carbides (including MC, M7C3 and M23C6) were also considered as possible crack nucleation sources due to the existence of incoherent boundary between these carbides and the ferrite matrix. Keywords: 4Cr5MoSiV1 steel, Uniaxial tensile, Crack deformation band, Crystallite, Carbides

Several examples have been chosen for presentation from a broad array of laser surface treatment technologies currently researched into and used in industry and the examples are distinguished by their extensive possibilities of future and current applications, especially in the tooling, automotive, and power industry. A newly developed methodology has been employed in order to make an objectivized assessment of the relevant laser surface treatment technologies. Contextual matrices and roadmaps and technology information sheets allowing for the mainly qualitative comparisons of the individual technologies according to harmonized criteria were created as a result of employing the methodology.

Climate conditions in workplaces are occupational health hazards that need to be taken into account when assessing population vulnerability to climate conditions and climate changes. Very cold as well as very hot work environments can create thermal stress beyond what human physiology can cope with. All human populations have a normal core body temperature in the range 36–37 °C, and even a few degrees higher or lower body temperature, due to surrounding climate conditions, can lead to serious health effects. Intrabody heat production creates vulnerability among people doing heavy physical labor. Increasing air temperature or humidity creates new workplace risks from heat stress, particularly in already hot locations, as temperature or humidity increases. This chapter describes this occupational health problem in some detail and also refers to other climate-related health risks that may occur in particular occupation groups.

Publisher Summary Open flames in a hydrocarbon facility are usually available from welding or hot work operations, smoking, and the facility flare. Additionally all petroleum facilities have limitations on areas allowed for smoking. These sources are normally controlled through operational measures supplemented by physical separation. Facility electrical systems and components provide a convenient source of ignition within a hydrocarbon or ordinary occupancies whenever the design, installation, or maintenance is substandard. Electrical systems or components may short, overheat, operate incorrectly, etc. These failures present themselves as available ignition sources for hydrocarbon vapor releases. All electrical installation should be according to the recognized electrical industry standards. The overall intent of the electrical area classification is to provide for safety of personnel and equipment. This is achieved by the elimination of electrical ignition sources near combustible gases or vapors that could explode or burn. It must be remembered that leakages may be large or small in nature and can be orientated in infinite directions, so considerable fuel releases may occur even where ignition sources are readily available. In addition, there are many incidents where large leakages occurred but have not ignited because ignition sources have been removed from the area. Therefore, prevention measures should be employed to avoid the ignition of a hydrocarbon liquid or vapors whenever possible.

This chapter focuses on accidents that occurred because equipment was not adequately prepared for maintenance. Sometimes the equipment was not isolated from hazardous materials, sometimes it was not identified correctly and so the wrong equipment was opened up, and sometimes hazardous materials were not removed. Various incidents have been outlined that reflect the failure in maintenance, human errors, or equipment itself. Summary of methods for maintenance of isolation is also provided to prevent causes of errors due to isolation failures. When an electrical supply is isolated, it is normal practice to check that the right switches have been locked or fuses removed by trying to start the equipment that has been isolated. On several occasions, maintenance teams have not realized that by isolating a circuit, they have also isolated equipment that was still needed. Need for tagging is highlighted when the wrong pipeline or piece of equipment has been broken into. Many accidents have occurred because equipment, though isolated correctly, was not completely freed from hazardous materials or because the pressure inside it was not completely blown off and the workers carrying out the repair were not made aware of this. Therefore it is usual to test for the presence of flammable gas or vapor with a combustible gas detector before maintenance, especially welding or other hot work is allowed to start. This chapter also describes incidents that occurred because of loopholes in the procedure for issuing work permits or because the procedure was not followed, and also points out the formal procedure to be followed.

Publisher Summary This chapter indicates that sometimes the accidents occur because some of the properties of the materials and equipment that are being used remain unknown to those who handle them. The chapter illustrates the properties of the materials by giving the examples of incidents where they were unknown. The various properties that it discusses are: that aluminium is dangerous when wet, that rubber and plastics are permeable, that some plastics can absorb process materials and swell, that static electricity is a common cause of ignition, that a little contamination can have a big effect, that unforeseen sources of ignition are often present, and the power of the compressed air. The chapter provides example of a fire that occurred in a packed column, packed with carbon steel where the fire was ignited by hot work and the fuel was the steel packing, possibly supplemented by process materials that had not been completely removed. In another example, contractors were removing water from a pipeline by pushing a foam pig along the line with compressed air. The water exit line was rather small, so the contractor opened up the end of the pig trap and put a large front end loader in front of it to catch the pig. The force on the pig was so great, nearly 250 tons, that the pig knocked over the loader and traveled another 150 m, destroying a wooden platform on the way.

SUMMARY The paper describes an experimental investigation into metal flow in forging. The operations considered are: upsetting between flat platens, upsetting between punches, and forging with a closed (impression) die. The objective of the study is to determine, in practical terms, those factors which affect the flow of metal restrained, in varying degrees, by a die. To the forging designer, this is a problem of considerable importance yet one which, in contrast to the study of deformation forces, has received scant attention as a research topic. The materials considered are lead worked at room temperature and steel at hot-working temperatures. The three forging operations will be examined as representative examples of three different types of boundary condition: upsetting between flat platens is affected only by friction and, in hot work, cooling on the contact faces; upsetting between punches has, in addition, restraint imposed by material outside the punches; and in closed-die forging the restraint of friction and cooling on the die walls is added. The fundamental changes to the flow patterns produced by these boundary conditions are examined. The work shows that friction, which is the dominant effect on flow patterns in upsetting between flat platens, assumes a negligible importance in upsetting between punches; then, the restraint of the material outside the punches becomes the most important factor and its geometry determines the shape changes during deformation. The work on closed-die forging shows that friction and cooling once again become important, but that their effects can be largely overcome by suitable choices of deformation pattern before contact with the die takes place. A simple analysis of shape changes is presented, based on the observed flow patterns, and the practical implications of the work discussed.