Effect of Design Modification on the Distortion Behavior of a Complex Counter Gear

A change in component design could help achieve objectives in lightweight construction. However, lightweight component design can incur serious distortion problems after the final heat treatment due to reduced stiffness or asymmetries in the mass distribution. The analysis of design modification through geometrical variations and their consequences on the distortion behavior through experiments can be costly and time consuming. In this paper, using 3D simulation models, different modified lightweight geometries are simulated. Using these simulation results, the authors try to understand the complex distortion behavior and correlate it with the effects of design modification.

Formation of Structure and Properties of 30HGSN2A Steel at Technological Stages of Manufacture of Heavy-Loaded Parts

The cases of premature failure of the barrel of liquid damper, made of complex alloyed high-strength 30HGSN2A steel, are analyzed. The options failure and the causes of their occurrence are established. Fatigue failure of the barrels during an operation is due to the failure of the chrome coating of the rod and the appearance of scorings on the surface of the barrel. Cases of failure of the barrels during official tests are associated with the reduced hardenability and an increased tendency to decarburize steel in the bottom of the barrel, due to the increased nitrogen content here (due to segregation). The influence treatment conditions on the structure and properties of steel are investigated. Modes of dehydration and final heat treatment of the products to eliminate their premature failures are recommended. The proposed conditions, in particular, include increasing the dehydration temperature to 200-230 oС, reducing the exposure time at the hardening temperature and reducing the tempering temperature, using vacuum heating.

Numerical Study to Understand the Distortion Behavior of a Weight-Reduced Counter Gear*

Objectives in the field of lightweight construction can be achieved by changing the component design, among other things. However, a design suitable for production would have to be taken into account, since serious distortion problems can occur after the final heat treatment due to reduced stiffness or asymmetries in the mass distribution. To illustrate this problem area, case hardening experiments using the example of a weight-reduced counter gear made of 20MnCr5 were carried out and have shown significantly different distortion behavior depending on the geometry and process parameters. However, it is difficult or even impossible to understand such a distortion behavior only through experiments, since many different variables can be responsible for dimensional and shape changes. In this context, a simulation tool can be very helpful to identify important variables that cause dimensional and shape changes and to understand the associated processes. This paper attempts to answer some open questions that arise from experiments on distortion behavior through simulations. ◼

Effects of Pre-Crack Depth and Hydrogen Absorption on the Failure Strain of Zircaloy-4 Cladding Tubes Under Biaxial Strain Conditions

Fuel cladding may be subjected to biaxial tensile stress in axial and hoop directions during pellet-cladding mechanical interaction (PCMI) of a reactivity-initiated accident (RIA). Incipient crack in the hydride rim assisted by the scattered hydrides in the metal phase may lead to failure of the cladding at small hoop strain level during PCMI. To get insight of such phenomenon, biaxial-EDC tests under axial to hoop strain ratios ranging from 0 to 1 were performed with pre-cracked (outer surface) and uniformly hydrided Zircaloy-4 cladding tube samples with final heat-treatment status of cold worked (CW), stress relieved (SR) and Recrystallized (RX). Results showed dependencies of failure hoop strain on pre-crack depth, strain ratio, hydrogen content and final heat-treatment status on fabrication, but no apparent dependencies were observed on the distribution pattern of hydrides (with similar hydrogen contents and hydrides predominantly precipitated in hoop direction) and the heat-treatment process for hydrogen charging. J integral at failure seems to be available to unify the effect of pre-crack depth.

INDUSTRIAL TECHNOLOGY OF MANUFACTURING ULTRA-STRENGTH NANOBAINITIC STEEL PLATES

Nanobainitic steel grades are a new construction material with a strength in the range of 1.9–2.2 GPa, at the same time characterised by good plasticity. Currently, the works on the development of nanobainitic steels at Łukasiewicz – IMŻ have entered the commercialisation phase. One of the main applications of ultra-strength nanobainitic steel plates is armour systems. In order to optimise the parameters of the production process of nanobainitic steel plates, microstructure examination and measurement of mechanical properties were carried out at intermediate stages of production and after final heat treatment. The results of industrial steel and plate production operations were assessed, including smelting and casting into ingot moulds, preparation of the rolling mill charge, hot rolling, plate production as well as intermediate and final heat treatment. Critical technological operations that may adversely affect the quality and performance of plates were identified. The directions for technology modification that reduce or eliminate threats of plate deterioration were formulated.

Improved cyclability of Nickel-rich layered oxides

ABSTRACTThis study compares the physico- and electro- chemical properties of LiNi0.8Mn0.10Co0.1O2 (NMC811) and LiNi0.83Mn0.06Co0.09Al0.1O2 (NMCA) prepared by an oxalic acid co-precipitation. Deposition of a SiO2 surface coating was attempted via reaction of the powder with an amino silane prior to the final heat treatment. It was found that either the presence of small amounts of Al3+, or the compositional gradient resulting from a two step co-precipitation, caused increased crystal growth of the NMCA in comparison to NMC811. This led to improved cyclability in LP40 electrolyte. However, the SiO2 coating appeared incomplete and negatively impacted performance. Crystal cleavage preferably on the {001} planes was observed after 100 charge-discharge cycles, with consequent cathode electrolyte interphase formation in the crystal cracks. This is believed to cause capacity decay via lithium loss, and increased charge transfer resistance. An FEC based electrolyte improved the cyclability in all cases and even under extreme conditions (45°C and upper cycling potential of 4.5 V) NMCA showed a capacity retention of 85% after 100 cycles.

Improving Strength of Structural Steels by Preheating in an Oxygen-Containing Medium

The results of the preliminary heat treatment effecting in a medium with a high oxygen content on the microstructure and mechanical properties of structural steels are presented. It is shown that the usage of preheating in the glass mass in the range of (Ac130°C) – Ac1for steels of grades 50 and 40H leads to the formation of a structure with dispersed granular pearlite and crushed excess ferrite precipitates. Such a structure, when heated for quenching, provides rapid formation of a homogeneous austenite and a delay in the growth of austenite grain, which provides the best combination of strength and plasticity after the final heat treatment. It is established that the tensile strength increases 1.2-1.3 times while maintaining the plasticity characteristics. The reliability of the obtained estimates of the mechanical property characteristics is confirmed by the results of a statistical analysis.

The Study Toughness Ecologicals Metals Materials

This aim of this is to determine the manner of realizing tubing pipe, which have to comply with suplimentary requirements concerning the notch impact strength at lower temperature (below - 300C). We realized �73 x 5.51 mm and �89 x 13 mm pipes applying various final heat treatment variants. For each heat treatment variant were determined the mechanical properties and the impact absorbed energy at temperatures between (-60 0C and +15 0C).