Increasing efficiency of plasma hardening by local cooling of surface by air with negative temperature
Journal Title: Восточно-Европейский журнал передовых технологий - Year 2019, Vol 4, Issue 12
Abstract
<p>The martensitic transformation interval of some hypoeutectoid, all eutectoid and all hypereutectoid steels covers to a large extent the region of negative temperatures. Due to the fact that the plasma hardening operation is carried out in workshops where the minimum temperature is +20 °С, the surface temperature of the part after plasma heating cannot reach negative values. Because of this, the temperature range of the martensitic transformation is not fully used and in the hardened structure there is a certain amount of austenite, which has not undergone martensitic transformation. This circumstance reduces the hardness of the hardened layer and often low tempering is required to convert residual austenite to tempered martensite, which lengthens and makes the heat treatment more expensive. Complete or almost complete martensitic transformation is possible if the surface heated by the plasma beam is immediately cooled to a negative temperature.</p><p>It is shown that local cooling of the hardened surface to a temperature of –40 °C can be carried out by air using the Ranque-Hilsch tube, which significantly expands the possibilities of full hardening for eutectoid and hypereutectoid steels. The studies consisted in heating the surface with a plasma stream to a temperature of 750 °C and 900 °C. The temperature was changed by the plasma torch current and by changing the velocity of the plasma flow spot moving along the sample surface. The experiments were carried out on steels 45 (0.45 % C), U8 (0.8 % C) and U10 (1 % C). The study of the structures was carried out on a MIM-7 microscope with a video camera and with the image displayed on the screen. The approximate quantitative composition of austenite, martensite, and associated structures was determined by the areas on the screen.</p>During plasma hardening of steel 45 from a temperature of 900 °C using the Ranque-Hilsch tube, there is practically no residual austenite in the structure. When hardening U8 steel, residual austenite is detected in a small amount. When hardening U10 steel, the amount of residual austenite is approximately 15 %. Local surface cooling allows high-quality hardening of steels of most grades, regardless of the carbon content.
Authors and Affiliations
Alla Bespalova, Vladimir Lebedev, Olga Frolenkova, Alexey Knysh, Oksana Fayzulina
Keywords
Related Articles
- EP ID EP667096
- DOI 10.15587/1729-4061.2019.176825
- Views 68
- Downloads 0
Design and study of the energyefficient unified apparatuses for energytechnological manufacturing
<p>The improved industrial sample of the rotor-pulse heat generator (RPH), integrated into the thermal heating systems of industrial buildings, was produced. Rotor-pulse generators do not occupy significant positions in...
Features of complex formation of a fibrous complexite with nickel ions in water–dioxane mixtures
<p>The study deals with the complex-forming properties of a fibrous complexing agent (complexite) NAG with respect to nickel(II) ions in a mixed solvent water-1,4-dioxane. Spectral tests indicate that the absorption of n...
Analysis of the properties of antifriction composites based on aluminum alloy's grinding waste
<p>We developed antifriction composites based on regenerated grinding waste of AM4.5Kd aluminum alloy with the addition of МоS<sub>2 </sub>solid lubricant intended for work in contact pairs of post-printing machines, suc...
Estimation of technological properties of nut meals and their effect on the quality of emulsion for butter biscuits with liquid oils
<p>We have examined the technological properties of cedar nut meal (CNM) and walnut nut meal (WNM). It was established that nut meals are the highly dispersed powders whose degree of dispersion exceeds that of wheat flou...
Investigation of the electrochromic properties of Ni(OH)2 films on glass with ITONi bilayer coating
<p class="1">Electrochromic films have been deposited onto glass coated with indium-tin oxide (ITO) and glass with ITO and a thin layer of metallic nickel deposited onto it. Nickel was deposited onto the surface of the I...