Effect Of Tempering Temperature Research Articles

Non-equilibrium phases in laser-processed Fe-0.2 wt.%C-20wt.%Cr alloys

The microstructures and microhardness of laser-processed Fe-0.2wt.%C-20wt.%Cr alloys were investigated as a function of melt depth in single and multiple (overlapping) laser passes. The single-laser-pass alloys exhibited duplex austenite-ferrite structures with no evidence of carbide precipitation. Melt depths of up to 600 μm did not influence this microstructure. The multiple-laser-pass alloys consisted of lath martensite-ferrite structures in deep (about 600 μm) penetration melts and austenite-ferrite structures in shallow (about 120 μm) penetration melts. The transformation of austenite to martensite in multiple-laser-pass alloys, observed only in deep penetration melts, was explained as due to the effects of tempering temperature, time and quench rate obtained during subsequent laser passes. Conventional furnace heat treatments of single-laser-pass alloys substantiated these conclusions.

高強度鋼の疲労き裂伝ぱ機構に及ぼす微視的組織の影響（疲労き裂伝ぱ速度と旧オーステナイト粒径との関連）

The fatigue crack growth rate was studied for high strength steel of different prior austenite grain sizes, from 34.2 to 238μm, produced by changing austenitizing temperature. The effect of tempering temperature and stress ratio on the growth rate was also examined.It was found that the variation in prior austenite grain size and the changes of tempering temperature had little effect on the fatigue crack growth rate at the mid-range of ΔK. At low (ΔK<30kgmm-3/2) and high (ΔK>80kgmm-3/2) ΔK regions of the materials tempered at 200°C, however, the crack growth rate was increased as the prior austenite grain size became fine. The threshold stress intensity factor, ΔKth, decreased with reducing grain size, and with increasing yield strength and stress ratio.Intergranular facets were formed in the both low and high ΔK regions regardless of tempering temperature. In this case, the area percentage of intergranular facets produced at the low ΔK region was correlated with ΔK, whereas the percentage at the high ΔK region was dependent on Kmax Morphology of intergranular facets seemed to be divided into four types which correspond to ΔK level. At the low ΔK region, a trace of twin deformation or smooth feature was found on the facets, while dimples and tongues were formed at the high ΔK region.

Effect of tempering temperature on the mechanical properties of high-strength tool steel

Steel D7KhFNSh is suitable for manufacturing parts operating under conditions of compression. The best combination of mechanical properties in compression is obtained by oil quenching from 840° and tempering at 170–200°.

Influence of metallurgical factors on the fast fracture energy absorption rates

The effects of tempering temperature on the crack-velocity dependence of dynamic fracture toughness have been studied for two high-strength steels: SAE4340 and 0–1 tool steel. In accord with previous results, the toughness associated with fibrous (dimpled) mode of crack extension increases with crack velocity, with the lower carbon level in SAE4340 resulting in higher toughness. In the experiments on SAE4340 the crack length at arrest was found to be in accord with values predicted by conservation of energy. As a consequence the stress intensity at arrest varies with crack propagation history.

Effect of tempering temperature on notch sensitivity of quenched steels

1. The variation of the notch sensitivity with the notch radius differs for quenched steels tempered at high and low temperatures. With a large notch radius the notch sensitivity of steel tempered at high temperature is close to unity and decreases sharply with decreasing notch radius. The notch sensitivity of steels tempered at low temperature remains low both with sharp and blunt notches. 2. The reason for the sharp reduction of the notch sensitivity with a small notch radius after tempering at high temperature is the formation of nonpropagating cracks. 3. After low-temperature tempering the second-order residual stresses favor nucleation of a fatigue crack at some distance from the surface, which in the presence of a stress gradient in the notch leads to an increase of the fatigue limit of notched samples and lower sensitivity to stress concentrations.

Effect of tempering temperature on the fatigue strength of high-strength tool steel

The use of heat treatment to obtain a high ultimate strength of machine parts operating under cyclic loading conditions is inexpedient, since raising the ultimate strength does not necessarily lead to a higher fatigue limit.

Structural characteristics and mechanical properties of carbon steel with niobium and vanadium

1. The addition of 0.6% V and 0.6% Nb to steel with 0.6% C (steel 60BF) resulted, after preliminary normalization at 850°, in an austenite grain size of 2.7 μ (grade 14) that was stable during heating to 850–1050° at rates of 20–60 deg/sec. Isothermal holding for as long as 180 sec at 950° does not lead to grain growth. 2. The austenite grain size of steel 60BF after quenching from 850–1050° is 2.5–2.0 μ. The austenite grain size remains essentially unchanged for the steel subjected to preliminary quenching or normalization. 3. The effect of tempering temperature on the mechanical properties of steel 60BF and 60 in relation to the austenite grain size was investigated. The steels with smaller grains have better properties at all tempering temperatures with the exception of 500–650°. Due to aging processes at these temperatures the ultimate and yield strengths and the modulus of elasticity are higher for steel 60BF with coarse grains than for the steel with fine grains.

Effect of tempering temperature on hydrogen permeability and brittleness of quenched steel (a discussion)

Effect of tempering temperature on hydrogen permeability and brittleness of quenched steel (a discussion)

Effect of tempering temperature on resistance to crack propagation in steel 18Kh2N4VA

Effect of tempering temperature on resistance to crack propagation in steel 18Kh2N4VA

Effect of tempering temperature on the corrosion of quench-hardened steel

Effect of tempering temperature on the corrosion of quench-hardened steel

The effect of tempering temperature, machining operations, and applied stress on the susceptibility of high-quality 1Cr12Ni2WMoV steel to stress corrosion

The effect of mechanical and heat treatment conditions and applied stresses on the stress-corrosion susceptibility of a high-quality 1Cr12Ni2WMoV-type chromium stainless steel widely used in power generating plants was studied. The effectiveness of the reagent used and its equivalent in relation to the actual working conditions of the steel studied were determined.

Limited impact endurance of 30CrMnSiNiN steel

The aim of this investigation was to study the effect of tempering temperature and metal purity on limited impact endurance under tensile loads at room and subzero temperatures. The tests were carried out on quench-hardened specimens of two grades of 30CrMnSiNiN steel: electric-arc smelted, i.e., in the initial condition (0.29% C, 1.3% Mn, 1.09% Si, 1.58% Ni, 1.04% Cr, 0.2% Cu, 0.012% S, 0.015% P, 0.01% O2, 0.01% N2) and subjected to a vacuum-arc refining (VAR) treatment (1.08% Mn, 0.007% S, 0.004% O2, 0.003% N2; the remaining impurities as in steel in the initial condition). VAR produces a substantial reduction in the content of O2, N2, S, and nonmetallic inclusions in the steel which, after this treatment, had a higher impact strength but virtually the same static strength properties.

Effect of tempering temperature on the structure and strength of quenched sintered steel

1. The optimum combination of strength characteristics in carburized sintered iron with a hypereutectoid case structure and 15% of pores is achieved after quenching in water and tempering at 300° C (σc=134, σt=62, σb=145 kg/mm2). Thus, the tensile and bend strengths of porous steel tempered at 300°C are more than twice those of untempered porous steel before and after quenching. 2. The optimum combination of ductility and impact strength characteristics in steel with 15% of pores, resulting from the formation of a granular temper pearlite structure, is achieved by quenching in water and subsequent tempering at 600° C (δ=7.6%, ak=1.1 kg-m/mm2).

鍛造焼入処理した機械構造用鋼の焼もどし温度と機械的性質

Investigation was made on the effect of tempering temperature on the mechanical properties of carbon steel, Mn steel, Cr steel and Cr-Mo steel which had been forge-quenched. The results obtained were as follows:(1) The temper brittleness of forge-quenched Mn steel, Cr steel and Cr-Mo steel was more clearly observed than normally quenched steels when the specimens were tempered in the temperature range of 300°∼400°C or 500°∼600°C. From the Load-Time Diagrams of Charpy impact tests, it could be deduced that the increase in brittleness of 300°∼400°C tempered specimens was caused by the reduction in the maximum loads (fracture resistance), and that of 500°∼600°C tempered specimens was due to the reduction in time to fracture (deformation to fracture). The increase in temper brittleness was not observed with forge-quenched plain carbon steel.(2) When the specimens either normally quenched or forge-quenched were subsequently tempered at 350°C for 50 hr, there was observed no distinct difference in the structures of carbides and the matrix between these differently quenched specimens of the steels studied. However, when they were subjected to the tempering at 550°C for 50 hr, the carbides of forge-quenched steels were more needle-like than those normally quenched, and more lath-shaped martensites were retained in the matrix.(3) Comparison of impact strengths was made with those steels which had almost the same hardness but quenched and tempered in different ways. As for the specimens harder than Hv 300, the impact value of the normally quenched steel was higher than the forge-quenched or high-temperature quenched steel. As for the specimens of less than Hv 300, the impact strength became lower in the order of the forge-quenched, normally quenched and high-temperature quenched steels.

Effect of tempering temperature on the hardness of 40Kh steel

Effect of tempering temperature on the hardness of 40Kh steel

蒸気タービン軸用Cr-Mo-V鋼の熱処理とクリープ破断強度について

Cr-Mo-V steel is widely used for h-p and i-p steam turbine shafts among many high temperature low alloy steels. And it has been recognized by our creep rupture test results of a number of steam turbine shafts that the creep rupture properties of large-sized Cr-Mo-V steam turbine shafts cover a considerably wide range. It is considered that this variance of the creep rupture properties is caused by the variance of the steel making procedures in a limited sense, that is the imperceptible differences of the melting practice, chemical composition, and heat treatment. To make clear the roles of these variables, a test program has been putting forword. The effects of tempering temperature on the creep rupture strength of a Cr-Mo-V steel is presented here.A Cr-Mo-V steel was austenitized at 950°C for 2h and cooled in a furnace at a rate of 100°C/h, followed by the tempering at 650°C, 675°C and 700°C for 3h. The micro structures were tempered bainite containing a little fraction of ferrite precipitates instead of the fully bainitic structure of actual shafts. The experiments were consisted of the creep rupture test, tensile test and V-notch Charpy impact test for the estimation of the fracture transition temperature. The creep rupture test was conducted with plain and notched bar specimen and the test results were arranged with Larson-Miller's parameter. The tensile test was conducted at room temperature and 538°C.The experimental results may be summarized as follows:(1) As the tempering temperature raised, the creep rupture strength of the plain bar specimen decreased, and the difference between 675°C and 700°C tempering was larger as was expected from the tensile test results and the microstructures of the steels.(2) The creep rupture strength of the notched bar specimens were little changed with tempering temperature.(3) In this range of tempering temperature and rupture time, notch rupture strength ratios at 538°C were more than unity, but the more the tempering temperature decrease, the more the notch rupture strength ratio tends to decrease. This means that there is every indication which shows the marked notch sensitivity of the Cr-Mo-V steel when the tempering was conducted at the comparatively low temperature.(4) The ratio of the creep rupture strength of plain bar specimen to the room temperature ultimate tensile strength was nearly constant irrespective of the tempering temperature. The ratio to the 538°C ultimate tensile strength slightly increased as the tempering temperature lowered, and this may be attribute to the stability of structure during the comparatively shorter rupture time. The ratios of the notched bar strength to the ultimate tensile strength at room temperature and 538°C were both gradually decreased with the lowering of the tempering temperature, according to its tendency to notch sensitivity.

軸受鋼の研究(IV)

The method for measuring the internal stress of the ring-type test pieces such as ball bearing was not established firmly, and so the calculating formula for measuring two demensional stresses of it was obtained.By using this formula, the effect of tempering temperature on the internal stress of the ring-type ball bearing steels was studied and the results were obtained as follows.(1) In case of oil quenching of the ring-type test pieces, the radial internal stress was very small in comparison with the circlumferential interna1 stress. The latter was tensionstress near the inner face. In quenching, the circumferential stress was about +76.9kg per mm2 (tenson) at about 1.4mm, and then about-28.3kg per mm2 (eompression) at about 5.5 mm from the inner face.(2) In case of the 130°C×1hr tempering, the internal stress increased about twice by the ε carbide precipitation. The circumferential stress was about +139.5kg per mm2 at about 1.4 mm from the inner face.(3) When the 180°C tempering ring-type test piece was compared with the 130°C tempering one, the former increased a little in the circumferential stress distribution. If the tempering temperature raised such as the above, the internal stress should be reduced by the stress relief. But the internal stress increased a little in fact. This cause was considered to be the expansion phenomenon that the retained austenite decomposed to martensite at 180°C×1hr tempering. It was necessary for the 180°C tempering to be avoided in the pratical heat-treatment.(4) In case of the 200°C×1hr tempering, the internal stress decreased in comparison with the 180°C and 150°C tempering.The circumferential stress was about +25.1kg per mm2 (tension) at about 1.4mm from the inner face.