Chromium Molybdenum Steel Research Articles

Manufacture of alloy steel tube by high frequency electric resistance welding.

The quality of chromium, chromium-molybdenum and austenitic stainless steel tubes manufactured by an electric resistance welding (ERW) is highly dependent on the sophisticated technologies of non-oxidizing welding, precise control of welding energy and smooth cutting of inside flush. In this report a newly developed manufacturing technology for ERW alloy steel tubes is described on the following items; oxygen content in the welding atmosphere for a non-oxidizing welding and its control equipment, appropriate welding energy and its control system and a high performance impeder.Furthermore, the quality of the mass-produced ERW alloy steel tubes by the new technology is investigated focusing on their corrosion resistance, high temperature creep rupture strength and fatigue strength.

Effects of Lead and Sulfur Components on Surface Durability of Case-hardened Chromium Molybdenum Steel Roller

In order to elucidate the effects of lead and sulfur components on surface durability of case-hardened chromium molybdenum steel SCM415 rollers, case-hardened rollers made of commercial SCM415 steel, special SCM415 steels with 0.056% and 0.169% lead and special SCM415 steel with 0.056% sulfur were fatigue-tested under a rolling with sliding contact condition. The experimental results were discussed by the calculated results about amplitude of ratio of shear stress to hardness. It was clarified that at a higher Hertzian stress range the fatigue life was shortened by addition of lead and sulfur to the steel but that at a lower Hertzian stress range the fatigue life was hardly affected by the addition of them.

Effects of Hardened Depth and Relative Radius of Curvature on Surface Durability of a Nitrided SACM645 Steel Roller

In this report, the effects of hardened depth and relative radius of curvature on surface durability of a nitrided aluminium chromium molybdenum steel roller are experimentally elucidated. The experimental results are discussed in terms of the amplitude of ratio of shear stress to Vickers hardness. The surface failure mode in this experiment was spalling due to a crack having its point of origin beneath the surface. The depth of the spalling crack agreed well with the depth of the maximum amplitude of the ratio of the orthogonal shear stress to Vickers hardness. The surface durability of the nitrided roller tended to increase as the hardened depth increases and the relative radius of curvature decreased.

A study on the effect of tooth fatigue on the dynamic performance of a gear pair. 3rd report In the case of nitrided aluminium chromium molybdenum steel gears.

Operational fatigue tests of nitrided gears were performed using a power circulating gear testing machine, in order to elucidate the failure mode, load carrying capacity and relation between tooth profile change and dynamic performance in the fatigue process of a nitrided aluminium chromium molybdenum steel gear. The failure mode was a tooth breakage by bending fatigue at the tooth fillet under a higher applied load and tooth breakage due to spalling near the pitch point under a lower applied load. The surface durability of the nitrided gear was within the range of that of case-hardened gears. The changes of tooth root strain, noise and vibration during the fatigue process were slight, since the change of tooth profile deterioration was insignificant.

Calibration of Nondispersive Infrared CO2Analyzers with CO2-in-Air Reference Gases

A set of eight CO2-in-air secondary standard calibration gases has been established by NOAA/Geophysical Monitoring for Climatic Change (GMCC) for use in its global CO2 monitoring program. Use of these gases obviates the need for pressure broadening corrections that arises when CO2 air sample analyses are performed with nondispersive infrared analyzers using CO2-in-N2 calibration gases. The gases are composed of clean mountain air, with suitably adjusted CO2 content, pumped into 49 1 chrome-molybdenum steel tanks to 150 atm pressure. Five of the tank gases have been calibrated manometrically at the Scripps Institution of Oceanography (SIO) to an accuracy of about ±0.10 parts per million (ppm). Calibration of the remaining gases is traceable to manometric primary standards maintained at SIO. The secondary standards are used periodically in Boulder, Colorado, to calibrate tertiary CO2 standards with which, in turn, field station standards and working reference gases are calibrated. Both the tertiary standards and the field station gases are commercially available CO2-in-synthetic-air gases which contain natural proportions of nitrogen, oxygen and argon. Calibrations by SIO since 1978 suggest that the CO2 of NOAA/GMCC secondary standard gases may be drifting at a rate of 0.05.ppm yr−1. Several CO2-in-air tanks used in Boulder for CO2 flask air sample analyses have exhibited drifts of up to 0.39 ppm yr−1. The CO2-in-synthelic-air reference gases appear to be more stable, generally exhibiting CO2 concentration drift rates of from 0 to 0.10 ppm yr−1.

Radiation damage and recovery of the mechanical properties of hardened Cr?Mo?V steel

1. In alloying of chrome-molybdenum steel with vanadium its radiation damage in the hardened condition is weakened in low-temperature (50–70°C) irradiation and strengthened with an irradiation temperature of about 300°C. 2. Restoration of the mechanical properties of steel irradiated in the hardened condition occurs during subsequent annealing at a higher temperature than in the same steel after hardening and high-temperature tempering, and with an increase in vanadium content the temperature of the start of restoration of the properties increases. 3. The experimental data obtained agree with the hypothesis of the influence of interstitial elements on the radiation damage of iron alloys and steel as a result of joining of vacancy-interstitial atom complexes or "molecular" type defects into vacancy-impurity accumulations.

Study on the Effect of Tooth Fatigue on Dynamic Performance of Gear Pair : 2nd Report, In the Case of Case-hardened Chromium Molybdenum Steel Gears

For elucidating the effect of tooth fatigue on dynamic performance of case-hardened gears, the gears were fatigue-tested by a power circulating gear testing machine, and tooth root strain, vibration acceleration level, sound pressure level and so on were measured. The tooth failure mode was classified into two types; a tooth breakage by bending fatigue at the tooth fillet and a tooth breakage due to surface fatigue near the pitch point. In the same failure mode, the changing pattern of sound pressure level was the same even if the surface hardening method was different. The dynamic load, vibration and noise tended to increase as the tooth profile deteriorated.

ニッケルクロムモリブデン鋼（ＳＮＣＭ４３９）のせん断強度のひずみ速度および温度依存性

The influence of strain rate and temperature on the flow stress of nickel chromium molybdenum steel (SNCM 439) was studied through experiments. In the experiments, thin walled tubular specimens of short gage length were loaded at strain rates of 70-103sec-1 in shear by using a torsional split Hopkinson bar apparatus, and loaded at strain rates of 10-4-10-1sec-1 by using a combined tension-torsion loading apparatus and an Instron testing machine. The experiments were performed in shear over the temperature range -185°C to 120°C.It is shown that the strain rate sensitivity of the yield point and of the flow stress in the region of small strain at -185°C and -60°C is remarkable, and that, below about -50°C, the influence of temperature on the flow stress reveal itself remarkably. It is confirmed that the experimental results obtained on the strain rate dependency and the temperature effect on the flow stress can be described fairly well with the practical constitutive equation for an elastic/viscoplastic body proposed by one of the authors. The values of the parameters contained in the constitutive equation are also presented.

Mechanisms of tempered martensite embrittlement in medium-carbon steels

The literature associates several mechanisms of fracture with tempered martensite embrittlement (TME). With the use of a series of chromium-molybdenum steels containing 0.3–0.5% C and the examination of heats containing nominally 0.002 and 0.02% P at each carbon level, this study has reproduced the transgranular and intergranular brittle modes of TME in 0.4 and 0.5% C steels and revealed a transgranular ductile mode of TME in the 0.3% C steels. Room temperature instrumented Charpy V-notch impact testing was used to detect TME, and together with fractographic characterization by scanning and transmission electron microscopy, showed that the nature of the crack initiation ahead of the notch was a key factor in differentiating the various mechanisms of TME. All of the observations could be explained by consideration of the effects of carbon content and tempering temperature on the carbide distribution and the matrix strain-hardening behavior of the steels. High phosphorus, by virtue of its segregation to retained alloy carbide particles and austenite grain boundaries during austenitizing, lowered impact toughness relative to low phosphorus specimens not just in the TME range but in all tempered conditions. Therefore, phosphorus, although shown to be potent embrittling element in hardened steels, is not responsible for TME.

Temper and Neutron Irradiation Embrittlement in 2¼ Cr–1 Mo Steels for Pressure Vessels of High-Temperature Gas-Cooled Reactors

A 2 1/4 Cr-1 Mo steel is a promising candidate material for structural components of the pressure vessel of the experimental very high temperature gascooled reactor (VHTR) in Japan. Since the service temperature of such components is expected to be about 400/sup 0/C, the behavior of the temper and neutron irradiation embrittlements in these chromium-molybdenum steels should be confirmed from the viewpoint of structural integrity. The experimental verification on the degree of the embrittlement due to thermal aging, including the effect of applied stress and neutron irradiation, is described. Steel containing substantial amounts (about 100 ppm) of phosphorus atoms, which are believed to cause the temper embrittlement, showed that applied stress enhanced the embrittlement due to thermal aging. Embrittlement caused by neutron irradiation appears to be minimal in the case of the material containing <1000 ppm of copper as impurity with neutrons irradiated at about 400/sup 0/C.

A contribution to the characterization of the surface oxide layers grown in natural conditions on chromium-molybdenum steels

Glow discharge spectroscopy (G.D.S.) has been used to analyse the thin oxide film grown in dry air on the surface of a chromium-molybdenum low-alloyed steel. The distribution of the elements in the film is described and their thickness is measured through a calibration by X-ray interferometry. The range of the film thickness is found to be about 25–65 Å. The influence of surface preparation (polishing, fine surface grinding) and of the exposure duration on the nature and thickness of the oxide films was investigated by glow discharge spectroscopy.

ホブ切り性におよぼす快削元素Ｓ，Ｐｂ，ＴｅおよびＣａの影響

The authors examined the influence of free machining additives in gear hobbing of chromium molybdenum steels with non-coated or TiN-coated HSS tools and obtained the following results.(1) The free machining additives sulfur, lead and tellurium increase the hob tool life, and sulfur and tellurium are more effective for it than lead.(2) Calcium is effective for only TiN-coated hob but it is not for non-coated hob.(3) Surface roughness of machined gear teeth is improved by adding sulfur, lead, tellurium and calcium.

Study on Effect of Tooth Fatigue on Dynamic Performance of Gear : 2nd Report, In Case of Case-Hardened Chromium Molybdenum Steel Gear

浸炭硬化歯車の疲労が動的性能に及ぼす影響を明らかにするため,動力循環式歯車試験機で疲労試験するとともに,歯元ひずみ,振動加速度,音圧レベルの測定などを行った。歯の損傷形態は,歯元での曲げ疲労折損と歯面疲労に起因したピッチ点近傍からの折損に二分され,損傷形態が同じであれば,表面硬化法が異なっても音圧レベル変化の様子は同じで,歯形の劣化とともに動荷重,振動,騒音などは増大する傾向を示した。

クロムモリブデン鋼の水素脆性感受性に及ぼす焼もどし温度の影響

クロムモリブデン鋼の水素脆性感受性に及ぼす焼もどし温度の影響

Study on Effect of Tooth Fatigue on Dynamic Performance of Gear : 1st Report, In Case of Induction-Hardened Chromium Molybdenum Steel Gear

Study on Effect of Tooth Fatigue on Dynamic Performance of Gear : 1st Report, In Case of Induction-Hardened Chromium Molybdenum Steel Gear

Study on the Effect of Tooth Fatigue on Dynamic Performance of Gear Pair : 1st Report In the case of induction-hardened Chromium Molybdenum Steel Gears

In order to elucidate the failure mode, load carrying capacity and relation between tooth profile change and dynamic performance in fatigue process of a surface hardened gear, operational fatigue tests were performed using induction-hardened chromium molybdenum steel gears, The failure mode in these experiments was pitting or tooth breakage due to tooth surface fatigue except one example in which tooth breakage occurred at tooth fillet. Tooth root strain, mode in tooth stress frequency distribution, noise and vibration increased as the tooth profile was degraded, and it was also made clear experimentally that the failure prediction by sound level change was difficult for the tooth breakage at tooth fillet and tooth breakage due to spalling.

炭素鋼およびクロム・モリブデン鋼の繰返し応力‐ひずみ挙動

Cyclic stress-strain curves were obtained by the incremental step method for a carbon steel SB 49 and a chromium-molybdenum steel SCMV 4. The temperature and strain rate dependences of the cyclic stress-strain curves were discussed and the curves were compared with those obtained by the companion specimens method. The conclusions obtained were as follows:(1) Cyclic hardening and cyclic softening behaviors were observed for SB 49 and SCMV 4, respectively. The cyclic stress-strain curve lay at the higher stress level side than the monotonic stress-strain curve for SB49; for SCMV 4 it was the other way.(2) The cyclic stress-strain curve depended on strain rate. With decreasing strain rate, the stress amplitude for SB49 increased at 200 and 300°C, but decreased at 400 and 500°C. Similar dependences were observed in SCMV 4 steel.(3) The cyclic stress-strain curve can be expressed very well by the experimental equation as Δεt/2=(Δσ/2)/E'+{(Δσ/2)/K'}1/n'(4) For both materials, the cyclic stress-strain curve obtained by the incremental step method coincided with that obtained by the companion specimens method.(5) The cumulative damage against the number of blocks to failure in the incremental step tests ranged from 2 to 1/2 for both materials.

Machining Performance of High-Rate Face-Milling Cutters with SWC Application

Summary To develop milling tools for high-rate machining of steels, prototype cutters with a special double-rake edge design using the SWC(Silver White Chip) cutting principle have been evaluated in milling tests of the low carbon steel SS41 generally used for weldments and the SCM440 chromium-molybdenum steel. Three kinds of indexable-type prototype cutters with ISO M2 grade inserts have been tested: they are, so-called “type-U” face-milling cutter intended for rough machining of The low carbon steel, “type-S” face-milling, cutter for medium carbon steels and alloy steels, and “type-SL” cutter for slot milling operation. Test results show that when proper cutting conditions are selected so as to form the built-up edge on the primary rake face, the cutting edge is free from the fragile chipping, and therefore the high-rate milling is possible. A double-rake edge of the prototype cutters is operated normally and attainstool life from 2000 to 10,000 cuts per edge at the metal removal rate several times greater than that of a convertional cutter edge. Machining power required by the SWC cutters is reduced by 20 to 38 to that by the conventional cutter. It will be possible to design cutters for practical use based on those test results.

ＳＷＣ切削法の応用による高能率フライスカッタの切削性能

To develop milling tools for high-rate machining of steels, prototype cutters with a special double-rake edge design using the SWC (Silver White Chip) cutting principle have been evaluated in milling tests of the low carbon steel SS 41 generally used for weldments and the SCM 440 chromium-molybdenum steel. Three kinds of indexabletype prototype cutters with ISO M 2 grade inserts have been tested: they are, so-called “type-U” facemilling cutter intended for rough machining of the low carbon steel, “type-S” face-milling cutter for medium carbon steels and alloy steels, and “typeSL” cutter for slot milling operation. Test results show that when proper cutting conditions are selected so as to form the built-up edge on the primary rake face, the cutting edge is free from the fragile chipping, and therefore the high-rate milling is possible. A double-rake edge of the prototype cutters is operated normally and attain tool life from 2 000 to 10 000 cuts per edge at the metal removal rate several times greater than that of a conventional cutter edge. Machining power required by the SWC cutters is reduced by 20 to 38% to that by the conventional cutter. It will be possible to design cutters for practical use based on those test results.

Chromium-molybdenum steels for fusion reactor first walls — a review

Chromium-molybdenum steels have recently become of interest as a first wall and blanket structural material for fusion reactors. This application will be assessed, and possible approaches on how CrMo alloys may be further developed for this application will be proposed. Generally, the CrMo steels can be divided into two categories: unmodified, basically CrMoC steels and CrMoC steels modified by the addition of carbide-forming elements. Extensive research and development efforts have been conducted on the unmodified steels, especially 2 1 4 Cr-1 Mo and 12 CrMo steels. Considerable work has also been done on 12 CrMo steels modified with additions of V, Nb, Ti and W. In recent years much of the research effort on this type of alloy has been directed at developing modified CrMo steels with less than 12% Cr (generally ⩽9%) for applications where the “stainless” properties imparted by chromium additions of at least 12% are not needed. We will examine the unmodified and modified steels in terms of hardenability, precipitation processes (stability at elevated temperatures), strength, and toughness. Where possible, we will discuss the effects of irradiation on these properties. Such a study leads to the types of tradeoffs that may be necessary between the well-researched unmodified 2 1 4 Cr-1 Mo steel and a high-chromium modified steel.