Showing papers in "Journal of Heat Treating in 1984"
TL;DR: A distinction is made between austempered ductile irons transformed at high temperatures and Austempered/bainitic ductile iron transformed at low temperatures in this article, which is a complex interaction between all heat treatment variables and chemical composition on a macroscopic and microscopic level.
Abstract: Recent interest in the development of austempered ductile cast irons has resulted in considerable study of the physical metallurgy and mechanical properties of these high strength, high toughness cast irons. Equally important is the identification of process control and quality assurance factors to achieve the desired properties successfully and consistently. In this study, aspects of austempered ductile iron quality control are reviewed including the production of quality ductile iron that will respond to austempering heat treatments, heat treatment process control variables to achieve the desired properties, and non-destructive techniques for quality assurance. A distinction is made between austempered ductile irons transformed at high temperatures and austempered/bainitic ductile irons transformed at low temperatures. Austempering response is a complex interaction between all heat treatment variables and chemical composition on a macroscopic and microscopic level. Alloying elements are essential to provide sufficient hardenability (or austemperability) for heavy section heat treatment. Austenitizing temperature as well as austempering time and temperature affect the transformation response for a given alloy. In addition, segregation causes a non-uniform transformation response within the material on a microscopic level. In many cases the final properties of austempered ductile iron can be directly related to the amount of stabilized (retained) austenite present in the final structure. Non-destructive techniques to measure stabilized austenite are discussed and evaluated. Problems associated with dimensional control for critical tolerance components are highlighted.
74 citations
TL;DR: In this article, the effects of metallurgical variables on both the structure and mechanical properties of austempered ductile irons having predominantly bainitic structures are described, on the basis of work carried out at BCIRA and elsewhere.
Abstract: The mechanical properties obtained in austempered ductile iron castings are dependent on metallurgical process variables, including metal composition and heat-treatment conditions. The former determines also, to a large extent, the size of section which can be fully transformed. The effects of these metallurgical variables on both the structure and mechanical properties of austempered ductile irons having predominantly bainitic structures are described, on the basis of work carried out at BCIRA and elsewhere. Areas where further work is required have been identified and include the need for more data concerning impact, fatigue, and fracture toughness properties. Some practical aspects of the heat-treatment of these materials are reviewed, and the potential of near-net shape casting processes is briefly examined. Further extensive exploitation of these materials, particularly as gears, will require close cooperation with design engineers and the development of foundry control and inspection methods to guarantee the integrity and properties of castings supplied to the user.
61 citations
TL;DR: In this paper, the variations of residual stresses and microstructures obtained by surface hardening with a 15kw, continuous-wave CO2 laser on samples of AISI 1045 (C43) and 40CD4 (40CD4) have been studied.
Abstract: The variations of residual stresses and microstructures obtained by surface hardening with a 15-kw, continuous-wave CO2 laser on samples of AISI 1045 (C43) and AISI 4140 (40CD4) have been studied.
36 citations
TL;DR: In this paper, the authors evaluated the contact fatigue properties of austempered nodular iron transformed at 230 °C to Rc 45-47 using roller contact fatigue tests and found that at a given load, contact fatigue life was 35 to 45 pct lower than carburized steel.
Abstract: Contact fatigue properties of austempered nodular iron transformed at 230 °C to Rc 45-47 were evaluated using roller contact fatigue tests. At a given load, contact fatigue life of the austempered iron was 35 to 45 pct lower than carburized steel. Shot peening, performed using 1.168-mm diameter Rc 45-55 cast steel balls to Almen strip intensity of 0.006 to 0.008 C, was not beneficial. An increase in the surface compressive residual stress introduced by shot peening was accompanied by surface roughening which lowered the fatigue life by detrimentally influencing the EHD film thickness. Stress induced white etching areas well known to develop in high carbon martensite were found to develop in bainitic microstructure also.
31 citations
TL;DR: In this paper, a variety of strength and toughness combinations are provided by the selection of Class 1, Class 2, and Class 3 heat treatments for structural plates and pressure vessel plates.
Abstract: Addition of 1.0/1.3 pct copper has been used for precipitation hardening in a lowalloy steel containing less than 0.07 pct C, 0.40/0.70 pct Mn, 0.6010.90 pct Cr, 0.70/1.0 pct Ni, 0.15/0.25 pct Mo, and at least 0.02 pct Nb. This steel is included in ASTM Specifications as A710 Grade A for structural plates and as A736 for pressure vessel plates. A variety of strength and toughness combinations are provided by the selection of Class 1, Class 2, and Class 3 heat treatments.
23 citations
TL;DR: In this article, the results from a number of heats of 12CrlMoV steel (DIN X20CrMoV121) have been described, concerning general features of the microstructure, in relation to the chemical composition and the heat treatment; microstructural changes due to thermal aging; and influence of melting method, product form, and size of the steel on structure and properties.
Abstract: The 12 pct Cr steels are attractive materials for advanted steam generators. In support of the DEBENE project for the development of a sodiumcooled fast reactor, a materials program is in progress to show the applicability of these steels. The program comprises mechanical, corrosion, and weldability tests. Additionally, extensive microstructural investigations are carried out, including optical microscopic examinations, scanning electronmicroscopy, and transmission electronmicroscopy on thin foils and extraction replicas are used. In this paper, some of the results, mainly obtained from a number of heats of 12CrlMoV steel (DIN X20CrMoV121) have been described. Information has been given concerning general features of the microstructure, in relation to the chemical composition and the heat treatment; microstructural changes due to thermal aging; and influence of melting method, product form, and size of the steel on structure and properties.
18 citations
TL;DR: In this article, 24 variations in the heat treatment of ASTM A710 Grade A, Class 3 steel were performed to determine how sensitive this alloy is to deviations from the recommended heat treatment.
Abstract: Twenty-four variations in the heat treatment of ASTM A710 Grade A, Class 3 steel were performed to determine how sensitive this alloy is to deviations from the recommended heat treatment and to form a basis for understanding property variations in the heat-affected zone of weldments. Tensile, impact, and hardness properties were measured for each heat treatment. Fractography and metallography were carried out to correlate microstructure with properties. It was found that smallangle neutron scattering was extremely sensitive to small changes in the microstructure and also correlated extremely well with properties.
13 citations
TL;DR: In this article, a spring steel with a small amount of niobium and vanadium added simultaneously into AISI9260 or SUP7 of the Japanese Industrial Standards is found to have a good sag resistance or resistance to a small deformation, during service for automotive suspension springs.
Abstract: A spring steel with a small amount of niobium and vanadium added simultaneously into AISI9260 or SUP7 of the Japanese Industrial Standards is found to have a good sag resistance or resistance to a small deformation, during service for automotive suspension springs. The two alloying elements bring about a retarded softening when quenched and tempered, which is the result of the precipitation of carbides of the two elements. Besides good sag resistance, which is evaluated by two methods, the steel has comparable characteristics to SUP7 in many respects, such as hardenability, fatigue properties, and so on. Reduction in the weight of the suspension springs is about 15 pct. The new spring steel has been used for some Japanese new models for two years, and the application is increasing.
11 citations
TL;DR: In this paper, a study of alloying effects in Cr-V rail steels has been carried out to determine the microstructural strengthening mechanisms, and it was found that vanadium microalloying produces a yield stress increment of approximately 90 MPa for low-nitrogen steels and 140 M Pa for high- nitrogen steels.
Abstract: A study of alloying effects in Cr-V rail steels has been carried out to determine the microstructural strengthening mechanisms. The laboratory steels investigated were based on the commercial 1 pct Cr rail steel chemistry (0.75C−0.8Mn−1 .25Cr−0.30Si) and represented two levels of nitrogen (nominally 0.007 and 0.015 wt pct) and two types of deoxidation practice. It is found that vanadium microalloying produces a yield stress increment of approximately 90 MPa for low-nitrogen steels and 140 M Pa for highnitrogen steels. This strengthening effect appears to saturate at or below 0.15 wt pct vanadium, with no further strength increase for higher vanadium concentration. The hardness and UTS exhibit the same variation with vanadium content as the yield stress. There is no consistent effect of aluminum content (deoxidation practice). Several distinct precipitate morphologies, a wide range of precipitate sizes, and a nonhomogeneous distribution of precipitates are observed. There is also significant partitioning of V, Cr, and Mn to cementite. It is suggested that an increase in the amount of coarse, austenitenucleated V(C,N) and possibly other coarse precipitate modes is responsible for the saturation of the vanadium strengthening effect.
7 citations
TL;DR: In this article, the CCT diagrams of steels were classified into four types and the temperature range in which rapid cooling is required for quench-hardening for each type of steel was determined and compared with the temperature ranges for the boiling stage in the quenching of steel, converted from the results obtained from a silver specimen.
Abstract: The features of cooling curves for oils using a silver specimen (JIS K-2242) were shown. The cooling curves of steel specimens for the same oils were also measured and compared with those of silver specimen. The CCT diagrams of steels were classified into four types and the temperature range in which rapid cooling is required for quench-hardening for each type of steel was determined and compared with the temperature range for the boiling stage in the quenching of steel, converted from the results obtained from a silver specimen. The V-value is defined as the ratio of the temperature range of the boiling stage to the temperature range which requires rapid cooling. The V-value is a better criterion for quench hardening in oil quenching for given steel than the H-value as a measure of quench severity.
7 citations
TL;DR: In this paper, the effect of room temperature aging on the stabilization and low temperature transformation of retained austenite in a low alloy steel (SAE 52100) was studied, and it was found that the amount of retained Austenite which transformed on subcooling to 250, 200, and 150 °K decreased rather rapidly as the aging time at room temperature prior to cooling was extended up to 16 hours.
Abstract: The effect of room temperature aging on the stabilization and low temperature transformation of retained austenite in a low alloy steel (SAE 52100) was studied. It was found that the amount of retained austenite which transformed on subcooling to 250 °K, 200 °K, and 150 °K decreased rather rapidly as the aging time at room temperature prior to cooling was extended up to 16 hours. Little retained austenite transformed by further extending the aging time at room temperature beyond 16 hours.
TL;DR: In this paper, the effects of oxygen-nitrogen sulfurizing on the wear of sintered iron were investigated and the results of tests run with and without lubrication demonstrate the marked improvement in wear resistance produced by this treatment.
Abstract: The effects of oxygen-nitrogen sulfurizing on the wear of sintered iron are presented. The results of tests run with and without lubrication demonstrate the marked improvement in wear resistance produced by this treatment.
TL;DR: In this article, the diffusion depth in sintered steels is greater than in comparable wrought steels, and the characterization of the diffusion layer was performed by X-ray diffraction analysis and Wickers microhardness measurements.
Abstract: Five wrought and eight sintered steels, comparable both in chemical composition and intended for similar mechanical applications, were manganized. By electron microprobe analysis it was verified, that for equal time and temperature, manganese diffusion depth in sintered steels is greater than in comparable wrought steels; alloying elements in sintered steels, as in wrought steels, promote manganese diffusion. The characterization of the diffusion layer was performed by X-ray diffraction analysis and Wickers microhardness measurements.
TL;DR: In this paper, the standard Jominy end-quench test was used to measure the hardenability of laboratory melted low- and medium-carbon steels, including a chromium-free, 0.44 pct carbon Ni-Mo series.
Abstract: The standard Jominy end-quench test was used to measure the hardenability of laboratory melted low- and medium-carbon steels. Steels tested included a 0.11 pct carbon Mn-Cr-Ni-Mo series, a 0.22 pct carbon Mn-Cr-Mo series, a 0.22 pct carbon Cr-Ni-Mo series, and a chromium-free, 0.44 pct carbon Ni-Mo series. Factorial design, analysis of variance, and multiple linear regression analysis were used to express ideal critical diameter (D1) as a function of composition and to detect significant alloy interaction effects. Molybdenum alloying did not cause large increases in D1 for the Mn-Cr-Ni-Mo series or the Mn-Cr-Mo series unless chromium, in combination with large amounts of manganese or nickel, was present, because much of the molybdenum effectiveness resulted from three-and four-way alloy interactions. The Mo-Ni two-way alloy interaction previously reported for low-carbon and medium-carbon steels was found in the Cr-Ni-Mo series and in the Ni-Mo series.