Final Hardening Research Articles

Formation of nanocoatings on pipeline valves by final plasma hardening

The influence of the spacing of parallel strips on the parameters of a reinforcing nanocoating is established for the example of the final plasma hardening of pipeline valves.

Effects of basic density, annual growth and drying schedule on selected quality factors of dried Siberian larch (Larix sibirica) timber

Siberian larch (Larix sibirica Ledeb.) timber is suitable for many uses in the mechanical wood industry. Drying it without any decrease in value, however, is difficult and slow. The purpose of this research was to compare the drying quality of Siberian larch timber dried with three different conventional schedules taking into account the density and annual growth of wood. Five drying tests were performed. The final moisture content (MC), MC gradient, cracks, deformations (bow, crook, twist and cup) and case hardening were measured from the dried timber. The basic density particularly affected the MC, as shown in the differences regarding dried wood, with the denser wood having higher final MC and MC gradient. It was also found that large annual growth increased some deformations. Most of the measured factors were best after drying at the highest temperatures used; however, a slightly different trend was observed for bow, twist and cup. MC factors and twisting were the most problematic properties in drying according to this study. Sorting Siberian larch timber, particularly according to density, would improve the MC properties of dried timber by ensuring sufficient drying time, as economically as possible, for each timber piece.

Final hardening of the contact surface of electric-motor commutators

Final hardening of the contact surface of electric-motor commutators

Using of Solid Detergent as an Economic Material and Environmentally Friendly Method Toward Lightweight, Slow Action and Anti Acid Concrete

Solid Detergent is one of the Economic materials and Environmentally friendly method towards enhancing properties of concrete. Lightweight, slow reaction and anti acid concrete can achieving by using this materials, so many test made to validate the advantage and disadvantage ; initial and final hardening time for cement mortar and compressive strength of concrete, also anti acid test made for cement mortar. The results of tests show this materials are suitable for achieving the purpose to lightweight, slow reaction additional anti acid concrete.

Optimization of the Chemical Composition of Cast Iron Used for Casting Ball Bearing Grinding Disks

The chemical composition of cast iron used for casting ball bearing machining disks was varied to optimize the properties such as castability, hardenability, and durability in ball machining. The cast iron characteristics were most strongly dependent on the Ni content and the carbon saturation degree, S c. This paper describes the types of test specimens, the working conditions, and the experimental results. The increase of the degree of carbon saturation reduces the tendency to form shrinkholes in the castings. The decrease in the Ni content negatively affects the final hardening treatment. A way to control solidification defects in cast iron, by reducing the Ni content, has been verified on cast disks.

Barothermomechanical treatment of high-strength titanium alloys

In the present work, the structurization processes determining the level of mechanical properties are investigated on the example of the VT22 (α + β) high-strength titanium alloy. The influence of regimes of plastic deformation under pressure on these processes is examined versus the deformation temperature. The influence of preliminary and final thermal hardening treatments is investigated.

Distortion of components due to segregations of a low alloy SAE 5120 steel after blank and case hardening∗

Abstract A conventional low alloy steel (SAE 5120, EN 20MnCr5) was investigated to determine length change and curvature during heat treatment due to segregations. Long cylindrical shafts were used to minimize the influence of the geometry. The shafts were taken eccentrically from semifinished bars with two different degrees of deformation. Two sets of multiple heat treatments were done for each deforming degree. One of them started with two slow cooling cycles and had a final blank hardening cycle. The other set was a slow cooling cycle and afterwards a case hardening cycle. Coordinate measurements were done before and after each heat treatment cycle. Significant differences in the length change as well as in the magnitude and direction of the curvature could be detected.

Field Measurements of Grout Pressures During Tunnelling of the Sophia Rail Tunnel

During drilling, grout pressures were recorded on a tunnel lining measuring 9.5 m in diameter. Two tunnel rings were fitted with pressure gauges (14 gauges per ring). Measurements were performed for more than one day. Final hardening of the grout did not occur during this time. The lowest pressures were measured at the start of the drilling process after completion of the ring. Results show that the grout pressure distribution is dominated by injection during drilling, but this distribution changes when drilling stops and buoyancy forces start to exert an influence. The influence of buoyancy forces increases further away from the injection points. Bending moments in the tunnel lining also influence the gradient in the grout pressure distribution.

EFFECT OF Al CONTENT ON WORK HARDENING IN AUSTENITIC Fe-Mn-Al-C ALLOYS

The work hardening curves of austenitic Fe-25Mn-(0.57-5.02)Al-0.15C alloys were measured from tensile tests at room temperature. These curves are described according to a model σ = σ0 +Kεn at lower strains and by one or two parabolic functions at higher strains.With an increasing Al content, the work hardening and work hardening rate for these alloys decrease markedly at high strains since the contributions of strain induced ε-martensite and deformation twins to the flow stress are lower. The work hardening rate increases slightly at lower strains except for the alloy with 0.57% Al in which the strain induced ε-martensite formed at lower strains leads to the high work hardening rate at higher strains.The addition of aluminum increases the stacking fault energy and phase stability in Fe-Mn alloys. Specifically, it suppresses the strain induced γ ε transformation and twinning which reduces much final strain hardening and enhances the dislocation cell structures which slightly improve the initial work hardening.On a mesuré les courbes d’écrouissage des alliages austénitiques Fe-25Mn-(0.57-5.2)Al-0.15C à partir d’essais de traction à la température de la pièce. On décrit ces courbes d’après un modèle σ = σ0 + Kε n aux plus faibles déformations et par une ou deux fonctions paraboliques aux déformations plus élevées.Avec une augmentation de la teneur en Al, l’écrouissage et le taux d’écrouissage de ces alliages diminuent significativement aux déformations élevées puisque les contributions à la contrainte d’écoulement de la martensite-ε d’écrouissage et des macles de déformation s’abaissent, même si le taux d’écrouissage augmente légèrement aux déformations plus faibles, sauf pour l’alliage ayant 0.57% d’Al pour lequel la martensite-ε d’écrouissage formée à plus basses déformations mène à un taux élevé d’écrouissage aux déformations plus élevées.L’addition d’aluminium augmente l’énergie de défaut d’empilement et la stabilité de phase des alliages Fe–Mn. Spécifiquement, elle supprime la transformation γ ε et le maclage induits par la déformation, réduisant de beaucoup le durcissement final et renforçant la structure des cellules de dislocation, ce qui améliore légèrement le durcissement initial.

FEM Modeling of Induction Hardening Processes in Steel

A modeling system for analyzing the integrated induction hardening processes was developed based on a general-purpose finite element program, with the capability to analyze the whole process from electromagnetic-induced thermal heating to final hardening. A coupled electromagnetic-thermal model was applied to study the induction heating process, which includes consideration of nonlinear material characteristics on temperature. Also, arrangement of AC current density distribution was conducted to simulate practical induction coil structure and magnetic concentrator effects to achieve desired heating patterns for later quenching and hardening analysis. Quenching analysis can provide cooling curve at any location in a heat-treated workpiece based on heat transfer principles. In hardening analysis, phase transformation was studied and an algorithm was developed to determine volumetric content of micro-structural constituents formed from austenitized phase in quenching process, based on analysis of the interaction between cooling curve and material time-temperature-transformation (TTT) diagram. Finally, hardness value was converted from martensite content based on a developed formulation. Validation was preliminary conducted based on comparison of hardening pattern of induction hardening of an automotive spindle with complex surface.

Nanotribological Properties of Octadecyltrichlorosilane Self-Assembled Ultrathin Films Studied by Atomic Force Microscopy: Contact and Tapping Modes

Atomic force microscopy, working in contact and tapping modes, has been used to probe the mechanical response of octadecyltrichlorosilane, CH3−(CH2)17−SiCl3 (OTS), self-assembled ultrathin films grafted on silicon-treated surfaces. To assess the adhesion hysteresis and the elasticity of the films, we have performed loading and unloading experiments in contact mode. The effect of compression is observed while the load is being applied to the film. Once the load is fully removed, the film remains compressed showing a clear deviation from perfect elasticity, with relaxation times in the range of 0.1 s. In the tapping mode, the loading/unloading experiments show again the deviation from perfect elastic recovery of the films. Upon loading, three different regions are encountered. These can be associated with an initial disorder of the chains produced by the indenting tip, followed by a smooth compression and a final hardening effect due to repulsive forces between the compressed chains. The tapping mode is als...

Expressions for predicting the residual stress in surface induction hardening of steel bars

A finite-element (FE) program is developed and used to analyse the distributions of residual stresses generated in the surface induction hardening of steel bars. It is found that there is no significant effect of the transformation latent heat and that the transformation induced plasticity (TRIP) reduces the compressive stress near the outer surface. The results with TRIP are in good agreement with experiment. Although many physical and mechanical parameters control the final microstructure and the residual stresses in the bar during surface induction hardening, the final residual stresses are mainly determined by the ratio of the hardening thickness to the radius of the bar and by the initial yield stress of the material. Based on a large number of FE numerical results, a set of simple formulae are given by use of the least-squares method. Instead of complicated FE analysis, the residual stresses in a bar induced by surface induction hardening can be easily predicted by use of these formulas from the final hardening thickness and the initial yield stress of the material.

Improvement of operating characteristics of quenched steels by combined surface plastic deformation

In recent years, new progressive technologies of hardening based on surface treatment of materials with high-energy fluxes (plasma, electron-beam, laser, electromechanical, etc.) have been applied more and more extensively. In many cases, this type of treatment leads to the formation of a specific high-strength state of the surface layer. However, it may also cause a decrease in both fatigue resistance and sensitivity to stress concentration. Therefore, surface plastic deformation (SPD) may be a quite useful final hardening operation. In the present paper, we study the prospects of the combination of electromechanical hardening (EMH) and SPD as applied to 45 steel with an initial hardness HV of 5 GPa subjected to quenching with low-temperature tempering at 473{degrees}K. The specimens underwent preliminary electromechanical treatment by local heating of the area of contact of a hard-alloy tool with the specimen surface at a current strength of up to 600 A. A high-strength 0.2-mm-thick layer with a hardness HV up to 9 GPa appeared as a result of thermal quenching of the surface layer because of extensive heat dissipation into the body of the specimen. Then cylindrical specimens with a diameter of 10 mm were subjected to SPD by two-stage rolling in a three-rollmore » device. The diameter of the rolls was 36 mm, the radius of curvature was 4 mm, and the force applied to the rolls amounted to 1 kN. Fatigue tests were carried out according to a pure-bending scheme as the specimen was rotated at a frequency of 50 Hz. As a result of preliminary electromechanical hardening, the endurance limit of the specimen increases by a factor of 5-7. At the same time, the fatigue resistance exhibits a substantial drop both in the region of limited endurance and at the endurance limit. This effect of electromechanical treatment can be explained by the inhomogeneity of the properties of the surface layer and the appearance of unfavorable residual stresses.« less

Plastic deformatioon in AlCuFe icosahedral phase

Plastic deformation of icosahedral AlCuFe has been studied by compression tests for temperatures ranging from room temperature to 750°C. Whereas at room temperature no ducibility is observed, the samples can be homogeneously deformed up to 130% at high temperatures with no final hardening stage. SEM observations reveal, at the ultimate stage of deformation, a vein pattern similar to the observed in amorphous metals but without slip bands or shear bands. Stress relaxation measurements shows to different regimes at low and high temperatures with a transition at 660°C. It is concluded from these experiments that dislocations are probably not responsible for the plastic deformation of icosahedral quasicrystals.

An intraoral lift technique for refining porcelain margins

A method has been described by which a paste of shoulder porcelain and light-curing resin is used to correct deficient porcelain margins. The resin-bonded porcelain is fired in an oven for final hardening.

Ultrastructure and histochemistry of blue‐green algae freeze‐substituted at 190 K by Nanoplast MUV 116

A method is presented for the infiltration and embedding of frozen micro‐organisms at a temperature of 190 K by Nanoplast MUV 116, a new UV‐polymerizable embedding medium for electron microscopy. The hardness achieved by UV irradiation in the cold is about 80% of the hardness needed for ultramicrotomy. Final hardening requires a post‐curing step at 333 K for 24 h.Applying this procedure to cyanobacteria, an improved ultrastructural preservation is demonstrated as compared to samples that were embedded in the water‐soluble medium Nanoplast FB 101 at ambient temperatures. Sections of materials treated in this way are suitable for histochemical techniques, such as Thiéry's silver staining method for glycogen.

Influence of ion-plasma treatment on the properties of copper spring alloys

1. Ion-plasma treatment of the surface before final hardening heat treatment is an effective method of increasing the strength properties of spring alloys. 2. The character of the surface treatment providing the greatest hardening effect depends upon the mechanism of hardening of the alloy. In dispersion-hardening beryllium bronze the greatest hardening is obtained in bombardment of the part surface with argon ions before final aging, and in alloys hardened by subrecrystallization annealing with application to the part surface of a thin layer of titanium by spraying in a nitrogen atmosphere with subsequent annealing in this atmosphere. 3. Ion-plasma treatment may be used in the production operation for hardening treatment of critical elastic elements.

A note on early hydration of cement

In this note it is shown that the hydration of portland cement and of blastfurnace slag cement can be traced using the flotation of cement from mortars and concretes. The various stages of the hydration reaction, i.e. initiation, induction period, formation of an initial gel structure and the final hardening process can be detected clearly.

Laboratory and Field Tests of CGA-72662 for Control of the House Fly and Face Fly in Poultry, Bovine, or Swine Manure12

CGA-72662, (N-cyclopropyl-1,3,5-triazine-2,4,6-triamine), an insect growth regulator, was very active against developing house flies, Musca domestica L., and face flies, M. autumnalis De Geer. Laboratory tests indicated that the LC50 to house flies exposed beginning with the egg stage was 0.42 ppm, and it was 0.04 ppm for face flies. No ovicidal or chemosterilant effects were observed. Face fly pupae were susceptible up to the point of final hardening. Topical treatment of poultry, bovine, or swine manure indicated that concns and rates ranging from 0.1% at 0.41 liter/m2 to 0.05% at 0.21 liter/m2 were effective in reducing subsequent emergence of muscoid flies. Feed-through trials using poultry receiving a rate of 1.5 ppm, or swine dosed at 0.5 mg/kg body weight/day, produced high level inhibition of house fly survival during the course of the chemical regimen. Manure from cattle fed CGA-72662 at 0.5 mg/kg/day produced more variable control of house flies.

Effect of Carbon Content on the Magnetic Properties of Iron-30% Cobalt-15% Chromium Alloys

Past studies have indicated that an alloy containing 55% iron-30% cobalt and 15% chromium could be substituted for the more costly Remendur alloy (48% Fe-48% Co-4% V) now being used in ferreed cross point switching devices. However, commercial utilization of this alloy has not been realized mainly because of difficulties in obtaining reproducible magnetic properties in cold worked rod or strip given a final hardening heat treatment. Data presented in this paper show that small amounts of carbon, in the range of 0.01%–0.1% by weight, have a pronounced effect on the magnetic characteristics of the alloy. With proper control over carbon content, degree of cold working, and final heat-treating conditions, it is possible to produce material having a remanence of over 16 500 G, coercive forces ranging from 30 to 55 Oe and a hysteresis loop squareness ratio greater than 0.90. Commercial trials are now underway to determine whether control over this additional parameter, carbon content, will yield material having the close tolerance magnetic properties needed for switching applications.