The alloying concept for low-density steels is simple in principle, but the production itself is usually complicated. The concept of adding aluminium to steel in large quantities has been used for many decades. This article introduces a new alloying concept for low-density steels. Based on model calculations, samples—or “heats”—with 0.7 wt% C, 1.45 wt% Si, 2 wt% Cr, 0.5 wt% Ni, and an aluminium content varying from 5 to 7 wt% are prepared. JMatPro software was used in combination with analytical techniques for experimental planning to design a suitable chemical composition for the low-density steels. Initial designs were based on the chemical composition of 54SiCr spring steel. The production of the experimental material was carried out in a vacuum induction furnace. The experimental heats were prepared by pouring into casts with dimensions of D = 110 mm, L = 500 mm. Basic thermophysical measurements are carried out on all the heats to determine the critical points of each phase transformation in the solid state, supported by metallographic analysis on SEM and LM or the EDS analysis of each phase. It is observed that even at very high austenitisation temperatures of 1100 °C, it is not possible to change the two-phase structure of ferrite and austenite.
Engineering gases are one of the indispensable tools for mass production as well as for applied and primary research. This lecture aims to provide an overview of some of the applications in manufacturing. The success of manufacturing technologies is usually not determined by quality parameters alone, but mainly by the overall added value and stability of production. There are often trade-offs that aim to best serve the customer, e.g.: cooling of thermal injections with liquid nitrogen, decarburization of transformer plates in controlled atmospheres, simple sensor measuring gas density even without the need for tempering.
This article discusses the possibility of creating a nanobainitic structure in massive items made of readily available steels of normalized grades. The possibility of combining the technology of producing a nanobainitic structure utilizing phase transformations with surface engineering techniques: carburization and nitriding, is also presented. The results of mechanical and functional properties' tests which served as the basis for selecting suitable steel grades and variants of nanobainitization treatment for practical applications, are shown. Prototype products made in nanobainitic steel technology, such as cold-work punches, screws, gears, inserts for dies for plastics, are demonstrated. The results of real-condition tests carried out on prototype items are presented and compared with the results obtained for steel items subjected to conventional martensitic hardening heat treatment.
Accelerated Spheroidisation and Refinement (ASR) process is alternative treatment to soft annealing. It leads to annealing structure with globular carbides. The main goal of this article was compare achieved properties after quenching and tempering among ASR process, conventional soft annealing and lamellar structure after hot rolling. It was done by hardness measurement and tensile tests. Microstructure evolution was observed by scanning electron microscopy (SEM). The ASR process led to refinement carbides size and homogenously distribution in ferritic matric. Finer initial structure brought advantage to quenching process. It resulted in lower quenching temperature and finer martensite by which they were obtained improved mechanical properties in comparing with soft annealing. In case of lamellar pearlite after hot rolling, the rate of dissolution was very similar. Nevertheless, ASR process led to improved ductility and reduction of area.
High borated stainless steels are widely applied in the nuclear power industry for transportation casks, and spent-fuel nuclear storage racks. Such containers have to exhibit both the high structural strength and the corrosion resistance, while keeping fuel assemblies subcritical at all times. The addition of boron isotope 10B to the steel provides the high thermal neutron absorption capability. On the contrary, due to the low solubility of boron in austenite matrix, boron precipitates as boride rather than dissolving in the matrix. Along with the low melting point of eutectic borides, a bad hot workability is a key issue in processing the steel. Another drawback of high borated steels is reduced corrosion resistance, especially when it comes to welded parts. It is essential to promote uniform fine grain structure and carbon free matrix without the presence of undesirable phases like delta ferrite.
Interstitial free steels (IF) and DP steels are widely used in the automotive industry, their specific application is driven by requirements to optimize the weight-to-strength ratio. Utilizing the full capacity of their plasticity and strain hardenability requires an assessment of edge fracture susceptibility and flangeability.
In this work, the ability of the mentioned steels to spreding of deformation along initiated cracks is evaluated by structural and fractographic analyzes. Microstructural restrictions of plasticity are correlated with fracture toughness results, adopting the essential work of fracture (EWF) methodology. Crystallographic analyzes (EBSD) are focused on the role of anisotropy and the of the deformation texture evolution, affecting the development of plasticity and thus the energy consumption to the fracture.
The aim of this paper is to show several special mechanical tests for the evaluation of steel degradation. The investigated materials are two austenitic creep-resistant steels - SUPER 304H and HR3C. Small sample methodologies will be demonstrated, namely the micro-tensile test (M-TT), mini-Charpy test, fracture toughness and dynamic E-modulus measurement. The mini-samples technique needs only small volume of material, which can be extracted by semi-destructive sampling with EDSE, so that the actual properties of component in service can be determined. Each type of test provides different, unique information about mechanical characteristics that change as the material degrades. Furthermore, the tests will be examined in terms of sensitivity to the degree of degradation and the most suitable test to capture the degree of degradation will be selected. This knowledge will help detect incipient degradation early in the process and a deep understanding and monitoring of material degradation will help predict better the remaining life of components in service.
The dissolution of carbides during the quenching process has a significant effect not only on the martensite oversaturation but also on the resulting mechanical properties. The kinetics of dissolution can be influenced by a number of external factors. This work deals with the comparison of the globular cementite dissolution during austenitization of 100CrMnSi6-4 bearing steel after accelerated spheroidization annealing ASR and conventional soft annealing. The experiments were carried out in a quenching dilatometer. Heating was either linear or simulated heating curve according to real industrial induction treatment. The main objective was to determine the amount of undissolved cementite during austenitization in the temperature range where only austenite and cementite are present in the structure. The austenitization temperature determines the degree of cementite dissolution, consequently the carbon content in austenite and thus final properties after quenching. The cementite dissolution was quantified from dilatometric curves. The finer carbides underwent austenitization more rapidly and the finer original austenitic grain was retained. Furthermore, the martensite start temperature Ms was monitored. In the case of the finer structure after accelerated ASR annealing, the Ms temperatures had lower values than in the case of the coarser structure after conventional soft annealing. More carbon dissolved into the austenite due to the smaller austenite grain size caused by the previous ASR annealing.