Non-magnetic Steel Research Articles

Formation of Fe56Mn5Cr7-Mo12Er2C12B6 amorphous steel

The Fe48Cr15Mo14Er2C15B6 amorphous steel can hardly be used as an engineering material because of its extreme brittleness and very low iron content. By changing the composition of the nonmagnetic amorphous steel, and using the relation between the reduced glass transition temperatureT rg and the glass forming ability, a new amorphous Fe56Mn5Cr7Mo12Er2C12B6 alloy with good glass forming ability and high iron content was obtained. The diameter of the as-cast sample rod reached 8 mm. This new amorphous steel has lower manufacturing cost due to its high iron content, and thus it can have wider applications.

Discovery and potential of nonmagnetic amorphous steel

Discovery and potential of nonmagnetic amorphous steel

Analysis of the Thin Plate Eddy-Current Problem by Finite Volume Method

The eddy-current distribution in a thin conducting nonmagnetic steel plate is calculated by using the finite volume method. Adopting finite volume methods, the governing equations are enforced along closed paths, and the simultaneous linear system with unknown nodes of current vector potential T can be formed in a very straightforward way. The numerical results show very good agreements with the experimental data of TEAM problem 21.

高画素カメラによる自動蛍光磁粉探傷装置の開発

It is necessary to inspect the surface defects of the billets which are partly finished products to warrant the surface quality. The fluorescent magnetic particle testing is used mostly to detect the surface defects of square non-magnetic steel billets. Writers have developed the advanced automatic inspection technique of fluorescent magnetic particle testing which uses the multi-CCD cameras. The original high-speed inspection (MG/CCD) system was introduced into the ERBIC(Efficient & Rationalized line of Billet Inspection and Condition) line of Chita Plant in 1993 with the tracking mirror system and the automatic threshold level decision processing. The further improved system is described in this paper and the view is focused on the equipment composition and the newly developed signal processing. The detection performance of a scab or a corner part is sharply raised by using eight Megapixel CCD cameras and advanced image-processing technology.

Compositional dependence of the Néel transition, structural stability, magnetic properties and electrical resistivity in Fe–Mn–Al–Cr–Si alloys

Compositional dependence of the Néel transition temperature, T N, structural stability, magnetic properties, and anomaly of resistivity, ρ, have been investigated in γ-Fe–Mn–Al–Cr–Si–C alloys. In the Fe–(20–32.5 at.%)Mn-based alloys, an increase in Mn, Al, Cr or C content will inhibit the γ→ε→α′ martensitic transformation and lower the ε martensitic transformation temperature M s or deformation-induced martensitic transformation temperature M d, while an increase in Si content promotes the γ→ε martensitic transformation and increases the M s and M d temperature. Manganese raises T N, decreases the susceptibility, χ, and slightly increases the anomaly of electrical resistivity, ρ. The temperature dependence of χ for Fe–Mn binary alloys shows a break at T N and χ becomes almost independent of temperature above T N. The effects of Cr on χ versus T and ρ versus T are similar to that of Mn but lowering T N. With increasing Al or Si content, T N decreases markedly; above T N, the magnetic state of the alloys changes from Pauli-paramagnetism to the Curie–Weiss behavior, and the anomalous ρ increases rapidly, leading to a negative temperature coefficient below T N. An empirical formula has been developed to express the compositional dependence of T N in γ-Fe–Mn–Al–Cr–Si alloys. The alloying elements that lower T N are in increasing order of severity, Cr, Al, Si and C. Manganese is the only element which both raises T N and decreases χ and M s. Adding up to 10 at.% Al to Fe–Mn based alloys strongly stabilizes the γ phase and retains antiferromagnetism down to 4 K. Increasing the Ni content of Fe–Cr–Ni steels improves their stability relative to the α′ martensitic transformation but induces a transition from the paramagnetic γ-phase to the ferromagnetic one at very low temperatures. Alloying Fe–Mn based alloys with Al and Cr exhibits an excellent combination of FCC structural stability, corrosion resistance and antiferromagnetism down to liquid helium temperature. The present results are valuable for the design of cryogenic non-magnetic steels and certain functional Fe–Mn based alloys.

Development of non-magnetic high manganese cryogenic steel for the construction of LHC project's superconducting magnet

High manganese steel (KHMN30L) as a cryogenic nonmagnetic material has been developed by Kawasaki Steel Corporation, which is designed for structural material for superconducting magnet in particle accelerator system. This steel satisfies the following requirements for the present use. 1) Low magnetic permeability: its relative magnetic permeability is lower than 1.002 throughout the range between 1.9 K and room temperature, and shows little temperature dependency which is the result of the highly elevated Neel temperature controlled by alloying composition design. 2) Low thermal expansion: its integrated contraction from room temperature to 4.2 K is as small as 0.18%. 3) Appropriate mechanical properties: yield strength and tensile strength can be adjusted to the desirable value by the manufacturing process condition without deteriorating physical properties. With these excellent properties, this steel is being supplied for nonmagnetic lamination of the cold mass of the LHC (Large Hadron Collider) superconducting dipole magnet, which is under construction by CERN.

Comparison between excimer laser irradiation effects in FeCr-based metallic glass and stainless steel

Pulsed excimer laser (248 nm, 8 ns) irradiation of Fe77Cr2B16Si5 metallic glass produces an out-of-plane reorientation of magnetic moment directions as well as changes in the resonant area of the Mössbauer spectra which depend on the irradiation time. Scanning electron microscopy (SEM) determinations linked these changes to the occurrence of molten zones subsequently resolidified. For comparison, Mössbauer spectra of the Fe/Cr18/Ni8/Ti magnetic steel showed additional features in the probability distribution of the hyperfine magnetic field, while the distribution of the Fe/Cr18/Ni8/Mo3 nonmagnetic steel remained unchanged after laser processing. For both steels, the distribution area in the Mössbauer spectra was found to decrease steadily as a function of irradiation time and the magnetic hyperfine fields showed maxima after 10 s/spot. SEM/EDX examination of the laser irradiated areas demonstrated that Ti atoms are displaced from these zones and suggest atomic rearrangements related to the features observed in the distributions of probability.

Transport and anisotropic properties of coated conductors deposited by PLD on steel substrates

Coated conductors deposited by a novel high-rate pulsed laser deposition (PLD) technique on ion-beam-assisted-deposition (IBAD) layers of yttria-stabilized zirconia (YSZ) on non-magnetic steel ribbons were investigated. An XRD analysis of the superconducting layers showed in-plane alignments with a FWHM from 10 to 25/spl deg/ and an out-of-plane alignment of better than 2/spl deg/. We report on the field and temperature dependence of the critical transport current density in these YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// films of various thickness. In addition, the angular dependence of the transport current at various external magnetic fields is presented. Thirdly, artificial pinning centers were introduced into the superconductors by neutron irradiation. The influence of these defects on the critical current densities and on the anisotropy ratio are discussed.

ＣＥＲＮ‐ＬＨＣへの日本の協力

The Large Hadron Collider (LHC) is now under construction at CERN, Geveva, to study frontier researches of particle physics. The LHC is the biggest superconducting accelerator using the most advanced cryogenics and applied superconductivities. The accelerator and large scale detectors for particle physics experiments are being constructed by collaboration with European countries and also by participation with non-CERN countries worldwide. In 1995, the Japanese government decided to take on a share in the LHC project with funding and technological contributions. KEK contributes to the development of low beta insertion superconducting quadrupole magnets and of components of the ATLAS detector by collaboration with university groups. Some Japanese companies have received contracts for technically key elements such as superconducting cable, cold compressor, nonmagnetic steel, polyimide film, and so on. An outline of the LHC project and Japanese contributions are described.

High-speed synchronous reluctance machine with minimized rotor losses

This paper presents a refined design of a high-speed synchronous reluctance machine with minimized eddy-current losses in the rotor. Design criteria are high power capability, ability of the rotor to withstand high speeds, ability to operate in vacuum, negligible zero-torque spinning losses, high reliability, high efficiency, and low manufacturing cost. The rotor of the synchronous reluctance machine consists of bonded sections of ferromagnetic and nonmagnetic steels. A finite element code, incorporating rotor rotation, has been developed in MATLAB that calculates steady-state motionally-induced eddy currents (and losses) in the rotor. A stator iron and stator winding have been designed to minimize rotor losses, and two such prototype machines have been fabricated. Experimental results show an efficiency of 91% at a 10 kW, 10000 rpm operating point, and negligible rotor heating.

Hydrogen cooling of turbogenerators and the problem of rotor retaining ring materials degradation

Hydrogen influence on fatigue crack propagation of the 8Mn8Ni4Cr (EFC21W) and 18Mn18Cr (P900) austenitic non-magnetic steels, which are the most widely used in the production of rotor retaining rings for turbogenerators was studied. Endurance limits and the crack growth rate of this steels on air, under electrolytic hydrogenation and dynamic loading has been investigated. Hydrogen enhances the micro brittle fracture of both 18Mn18Cr and 8Mn8Ni4Cr steels, but modern 18Mn18Cr steel exhibits a higher hydrogen embrittlement resistance as well as higher fatigue resistance on air.

Study of vacuum levels in the annealing of high silicon (6.4 wt%) non-oriented magnetic steel sheets obtained by rapid quenching and its incidence on grain size, texture and core losses

In the present study, high silicon (6.4 wt%) – iron microcrystalline ribbons (25 mm×38 μm) were obtained directly from its melted state by rapid quenching. The material thus obtained was then submitted to heat treatment. This soft magnetic material is mainly used as cores in high-performance electric machines (50–400 Hz.). At this stage of the heat treatment, the effect of the vacuum level (10 -3–30 Pa) and temperature range (950–1250°C) on grain size and developed texture as well as the resulting influence on the amount of total core losses (1.0 T, 10–1000 Hz) were studied. The obtained results show two types of recrystallization, primary and tertiary, which are both controlled by vacuum level and temperature range. The process of tertiary recrystallization is further divided into three differentiated subtypes, according to the developed texture and core losses obtained. In the case of tertiary recrystallization (1–20 Pa, 1050–1100°C), which also shows the highest percentage (70–90%) of texture {1 0 0}〈0 k l〉 and a grain size between 800 and 1100 μm, the minimum amount of magnetic core losses is obtained. These core losses (1.0 T, 50 Hz) are lower (60–65%) than those obtained with the top grade (FeV-240-35HA) of conventionally processed (≈3 wt% Si) non-oriented magnetic steel sheets. This difference in the amount of core losses increases as the work frequency rises.

Mechanical properties and damage behavior of non-magnetic high manganese austenitic steels

Fe–Cr–Mn steels have been considered as materials of structural components for fusion reactor because of their low induced-radio-activity compared with SUS316 stainless steels. It has been expected to develop a non-magnetic steel with a high stability of the austenitic phase and a strong resistance to irradiation environments. For these objectives, a series of the Fe–Cr–Mn steels have been examined by tensile tests and simulation irradiation by electrons. The main alloying compositions of the steels developed are; C:0.02–0.2 wt%, Mn: 15 wt%, Cr: 15–16 wt%, N: 0.2 wt%. These steels were heat-treated at 1323 K for 1 h. The structure of the steels after the heat-treatment was austenite single phase. The yield stress of the steels was 350–450 MPa and the elongation were 55–60%. When the steels of high C and N was electron-irradiated at below 673 K, no voids were nucleated and only small dislocation loops were formed with high density. The austenite phase was also stable during irradiation below 673 K. Thus, newly developed high manganese steels have excellent mechanical proprieties and high irradiation resistance at relatively low temperature.

Low-activation Mn–Cr austenitic stainless steel with further reduced content of long-lived radioactive elements

Low-activation austenitic stainless steel based on Mn–Cr non-magnetic steels has been developed. The alloying elements of long-life activation, such as Ni, Mo and Co, were eliminated and substituted with Mn along with an addition of N. A Mn–Cr austenitic stainless steel, 24.5Mn–13.5Cr–0.02C–0.2N, has been developed successfully. Examined material properties, including mechanical, thermal and magnetic properties, as well as weldability and characteristics of corrosion resistance, are presented. It was found that the alloy has excellent material properties virtually equivalent to those of 316SS. In this study, the applicability of the Schaeffler, DeLong and Hull constitution diagrams for the stainless steels with low Ni and high Mn contents was also examined. The boundary conditions distinguishing the single austenite phase from the others have been identified for the Mn–Cr steels.

Incidencia del recocido bajo atmósfera de nitrógeno en el tamaño de grano, textura y pérdidas en el núcleo (10-1000 Hz) en cintas microcristalinas Fe - 6,4 % Si obtenidas por solidificación rápida

In the present research, high silicon (6.4%) - iron microcrystalline ribbons were obtained by rapid quenching. In this material the incidence of the atmosphere (N 2 ) and the annealing temperature (900-1,100°C) on the micrographic structure, grain size and texture and, as a consequence, in the total core losses ((1.0 T) 10-1000 Hz) were studied. The analysis of the results shows that the core losses are, in all cases, lower than those of the highest grade of conventionally processed nonoriented magnetic steel sheets, this becoming specially noticeable in the frequency range between 50-400 Hz.

Corrosion-mechanical characteristics of the materials of nonmagnetic retaining rings of turbogenerators. II. High-nitrogen 18Mn−18Cr steels

The optimal composition which maintains the necessary service characteristics of austenitic nonmagnetic steels for retaining rings of powerful turbogenerators must contain at least 18% Mn, 18% Cr, and 0.6% N. Chromium has a significant influence on corrosion cracking, relaxation, and erosion resistance. In more complex alloys with additions of nickel, molybdenum, and niobium, chromium considerably changes plasticity in bending, which is caused by the ability of the alloy to resist forgerolling (rigid cold stretching) used for the achievement of a high yield limit of a retaining ring. The technology of nitration under pressure in the process of electroslag remelting allows one to reach a content of nitrogen which is much greater than the solubility of nitrogen in steel under normal conditions. By using a special recrystallizing (mechanical and thermal) treatment and strain strengthening of blanks by hydraulic tension, we suppress the formation of a coarse-grained structure and ensure fine grains of eight-nine number. An amount of vanadium of up to 1% promotes mechanical strengthening. Together with nitrogen, it stimulates precipitation hardening and improves the high-strength state of chromium-manganese steels without perturbation of their fine-grained structure, which makes its application promising for increasing resistance to corrosion cracking. In cooling steel, we observe anomalies of physical properties caused by phase transitions at temperatures of −100 and −10°C accompanied by changes in the symmetry of the lattice and magnetic structure.

Mechanical properties and fatigue strength of high-manganese non-magnetic steel/carbon steel welded joints

Summary This paper describes performance tests of dissimilar material welded joints produced from carbon steel and a new type of high-manganese non-magnetic steel with improved machinability. The basic mechanical properties of these joints are first described. Fatigue tests are then conducted for purposes of fatigue strength design of the joints within the context of an evaluation of their suitability for application to welded structures, such as the steel bridges of magnetic levitation railways (linear motors). Dissimilar material welded joints with good penetration and integrity arc obtained. The results of the surface colour check and X-ray transmission tests of the welds suggest that they are free from any welding defects, such as hot cracking or blowholes. The tensile strength of the dissimilar material welded joints is, at 498 MPa, 10% higher than that of the carbon steel base metal (441 MPa). In the bending tests, the dissimilar material welded joints show good ductility without cracking under face, root, or side bending. The Charpy absorbed energy at 0°C of the dissimilar material welded joints is over 120 J even in the bond, where it appears to be lowest. No significant hardening or softening was detected in the heat affected zone. The fatigue strength of the dissimilar material welded joints is equivalent to that of carbon steel similar material welded joints. Since the fatigue strength of the dissimilar material welded joints exceeds the fatigue design standard curves of the JSSC for carbon steel welded joints, they can be treated in fatigue design terms the same as carbon steel similar material welded joints whose strength is lower than that of high-manganese non-magnetic steel.

Ｘ線材料強度 高マンガンオーステナイト鋼の疲労破面におけるＸ線フラクトグラフィ

Fatigue tests were carried out under constant stress amplitude, using a non-magnetic high manganese Mn-Cr steel. X-ray fractography was applied on the fatigue fractured surface to investigate the relationship between stress intensity factor and residual stress or half-value breadth of the X-ray diffraction profile. The fatigue crack propagation rate of this non-magnetic Mn-Cr steel had the same tendency as in the ordinary structural ferritic steels. The relationship between stress intensity factor and the residual stress or half-value breadth of the steel was almost the same as that of the ferritic cyclic work hardening steels. No stress induced transformation was observed on the fracture surface, but the residual stress on the fractured surface was compressive in the high stress intensity factors range, which is typical in the cyclic work hardening steels. The half-value breadth on the fractured surface increased with increasing effective stress intensity factor range. The relationship between the half-value breadth and stress intensity factor range was represented by a linear line regardless of the stress ratio. Therefore, the acting stress intensity factor range at the time of fracture can be estimated from the half-value breadth. The depth of monotonic plastic zone was estimated from the distribution of half-value breadth beneath the fractured surface. The relationship between the maximum stress intensity factor and half-value breadth was expressed by the equation ωm=α(Kmax/σy)2, where the value of α was 0.025. This is about one sixth of the value for ferritic steels, and the fact shows the severe work hardening occuring in the plastic zone in this manganese steel.

Performance Characteristics of an X-Y Linear Pulse Motor Using Air Bearing

This paper deals with the performance characteristics of a two-axis linear pulse motor (X-Y LPM) using air bearing. The mass, M, of the mover of X-Y LPM is 1.35 kg and the maximum static thrust, Fs, is 48.5 N with two-phase excitation at 2 A. The maximum velocity of the mover, v, is 1.4 m/s and the maximum acceleration, a, is 14.3 m/s2 at a velocity of 1 m/s without any load. The kinetic thrust, Fk, is 19.3 N. A non-oriented magnetic steel sheet, 50A350, is used as the core in the mover, and rolled steel for general structures, SS400, is used as the stator. The maximum flux densities, Bm, of 50A350 and SS400 are 1.45 T and 0.123 T, respectively, in a magnetic field with a maximum intensity of 1 kA/m and at a frequency of 1 kHz. The material of the stator must have a high magnetic flux density at the driving frequency to achieve high velocity and high-thrust driving of the X-Y LPM.

高Ｍｎ非磁性鋼と炭素鋼との溶接継手の継手特性と疲労強度

The dissimilar materials welded joints of high manganese non-magnetic steel/carbon steel (hereafter refered to as DMW joints), in which weld defects such as hot crack or blowhole are not found, were the good quality. Tensile strength of DMW joints was 10% higher than that of the base metal of carbon steel. In the bend tests, the DMW joints showed the good ductility without crack. Charpy absorved energy at 0(°C) of the DMW joints was over 120 (J) in the bond where it seems to be the lowest. Large hardening or softening was not detected in the heat affected zone.Fatigue strength of the DMW joints is almost the same with that of the welded joints of carbon steel/carbon steel. As the fatigue strength of the DMW joints exceeds the fatigue design standard curve of JSSC for carbon steel welded joints, the DMW joints can be treated the same as the welded joints of carbon steel/carbon steel of which strength is lower than that of high manganese non-magnetic steel, from the viewpoint of the fatigue design.