Conventional Carbon Steel Research Articles

Advanced type stainless steel 316FR for fast breeder reactor structures

Low carbon and medium nitrogen type 316FR stainless steel has been developed for structural materials of fast breeder reactors (FBR). In order to elucidate the relationship between creep rupture properties and microstructures, the microstructural changes of 316FR steel have been investigated in comparison with conventional medium carbon and low nitrogen type SUS316 steel. Creep rupture tests were conducted at 550 and 600 °C. The microstructures of ruptured specimens were examined with an electron microscope and the solute concentrations were assessed by analyzing extracted residues. The 316FR had higher rupture strength and ductility than SUS316 for long-term creep. Laves phase precipitated mainly on the grain boundary at 550 and 600 °C and also in matrix after 10 000 h creep at 600 °C in 316FR. Laves phase on the grain boundary did not decrease rupture ductility. The solid solution hardening by nitrogen was effective for a long period of time, because of the extremely small amount of nitrides precipitated during creep. On the other hand, large amount of carbides precipitated on the grain boundary and in the matrix of SUS316. They caused loss of the rupture strength due to the decrease in solute carbon content. The precipitation of carbides on the grain boundary resulted in loss of ductility because of the grain boundary embrittlement. In conclusion, the reason why 316FR had higher rupture strength and ductility than SUS316 was due to the higher phase stability during high temperature exposure.

Towards an austenite decomposition model for TRIP steels

The current status of developing a fundamental model for describing the overall austenite decomposition kinetics to ferrite and carbide‐free bainite in low carbon TRIP steels alloyed with Mn and Si is reviewed. For ferrite growth, a model is proposed where both interface and carbon diffusion‐controlled ferrite formation are considered in a mixed‐mode approach. The kinetic model is coupled with Thermocalc to obtain necessary thermodynamic information. Spherical geometry with an outer ferrite shell is assumed to capture in a simple way the topological conditions for growth. The mixed‐mode modelling philosophy has been identified to permit a rigorous incorporation of the solute drag effect of substitutional alloying elements, in particular Mn. The Purdy‐Brechet solute drag theory is adopted to characterize the interaction of Mn with the moving austenite‐ferrite interface. The challenges of quantifying the required solute drag parameters are discussed with an emphasis on a potential solute drag interaction of Mn and Si. The model is extended to non‐isothermal processing paths to account for continuous and stepped cooling occurring on the run‐out table of a hot strip mill or on a continuous annealing line. The transformation start temperature during cooling is predicted with a model combining nucleation and early growth which had previously been validated for conventional low carbon steels. The overall model is evaluated by comparing the predictions with experimental data for the ferrite growth kinetics during continuous cooling of a classical TRIP steel with mass contents of 0.19 % C, 1.49 % Mn and 1.95 % Si. Extension of the model to include bainite formation remains a challenge. Both diffusional and displacive model approaches are discussed for the formation of carbide‐free bainite. It is suggested to develop a combined nucleation and growth model which would enable to capture a potential transition from a diffusional to a displacive transformation mode with decreasing temperature.

Fatigue behaviour of laser welds of high-strength low-alloy steels

High-strength low-alloy (HSLA) steels are a group of low-carbon steels designed to provide better mechanical properties and sometimes better corrosion resistance than conventional carbon steels. The laserbeam welding of HSLA steels can improve the productivity, increase the process reliability and avoid deformation in several industrial fields, as structural components, pressure vessels and linepipes, and in shipbuilding and offshore construction. An exhaustive analysis of the mechanical behaviour of welded joints from different points of view must be carried out for these processes to be able to go ahead. The behaviour of the laser welded HSLA steel studied is good, with a fatigue limit under the present test conditions of 260 MPa. Cracks usually start in the fusion zone, near to the borderline between the fusion zone and the heat-affected zone, the cracks growing right into the base metal by the transcrystalline cracking process.

Large-Scale Wet Hydrogen Sulfide Cracking Performance: Evaluation of Metallurgical, Mechanical, and Welding Variables

Abstract The serviceability of welded steel equipment in wet hydrogen sulfide (H2S) service was studied. Large-scale exposure tests were conducted using a steel pressure vessel containing various welded test plates. Effects of variables including steel base plate composition, metallurgical processing, welding, applied stress, and orientation were examined. Particular attention was given to large-scale behavior vs behavior for small-scale laboratory test specimens under an applied tensile stress; performance of conventional carbon steels (CS) vs advanced CS designed for enhanced resistance to hydrogen-induced cracking (HIC); and the interrelationship of stress, welding, and plate orientation on susceptibility to wet H2S cracking. Results provided insight on the role of steel quality and microstructure in susceptibility of CS to HIC, stress-oriented hydrogen-induced cracking (SOHIC), and sulfide stress cracking (SSC).

High-Temperature Properties of Stainless Steel for Building Structures

This paper reports high-temperature properties of stainless steel for structural use in comparison with conventional carbon steels. Because of the elements contained, stainless steel retains streng...

フェライト鋼における疲労特性におよぼす微視的強化機構の影響

Ultra-low carbon steel containing phosphorus and copper (P-Cu steel) has both a higher fatigue limit and better crack propagation resistance than conventional low carbon steels with the same tensile strength. In this paper, the mechanism for improving the fatigue properties of P-Cu steel is discussed on the basis of microscopic observations by electron microscope and measurements of crack closure behaviour for small and long fatigue cracks. The excellent fatigue limit and small-crack propagation resistance in P-Cu steel can be attributed to solution hardening caused by phosphorus and precipitation hardening caused by ε-Cu. On the other hand, the superior resistance to long-fatigue crack propagation was caused by grain coasening which occurs with reduction of carbon content, leading eventually to roughness-induced crack closure.

ChemInform Abstract: Influence of Nitrogen and Molybdenum on the Sensitization Properties of Low‐Carbon Austenitic Stainless Steels.

AbstractIt is reported that for conventional low carbon steel (0.03%), as well as steels with higher carbon contents (0.05%), the addition of nitrogen (up to 0.123%) improves significantly the resistance to sensitization.

Recrystallisation textures in iron resulting from nucleation at grain boundaries

The influence of prior grain boundaries on nucleation of recrystallisation and associated texture development in iron has been investigated using deformed bicrystal specimens. The samples were designed to simulate as closely as possible the conditions of orientation and geometry existing in heavily cold rolled polycrystals. In all cases nucleation occurred preferentially at grain boundaries and resulted in well defined recrystallisation textures. The most significant finding was that components of the 〈111〉//ND γ-fibre texture gave rise to new orientations within the same fibre spread rotated ~30° around the normal direction. No evidence was found of systematic lattice rotations adjacent to the grain boundaries in the deformed state. The texture evolution is interpreted in terms of a compromise between the frequency of potential nuclei and their respective growth velocities. Present results permit rationalisation of several important aspects of texture development in conventional low carbon steels.

The influence of nitrogen and molybdenum on the sensitization properties of low-carbon austenitic stainless steels

The electrochemical potentiokinetic reactivation technique has been applied to the quantitative assessment of the influence of nitrogen and molybdenum on the sensitization properties of low-carbon austenitic stainless steels. The resulting isosensitization curves show that the addition of nitrogen (up to 0.123%) significantly improves the resistance of molybdenum-containing austenitic stainless steels to sensitization. This effect also occurs in conventional low carbon (0.03%) steels, as well as in steels with a higher carbon content (0.05%). Furthermore, it is shown that additions of molybdenum (up to 2.3%) to nitrogen-containing steels improve their resistance to sensitization by retarding the precipitation of chromium carbides.

希土類元素を添加した黒鉛鋳鋼の特性

In order to develop a free machining cast steel which has higher elastic stiffness and strength than cast iron, rare earth metal (REM) treated graphite cast steels were developed and its characteristics were investigated. REM treated graphite cast steel has more finely and uniformly distributed spheroidal graphite than cast iron or graphite cast steels treated with Ca or Mg. REM treated graphite cast steel which contains 1.0%C and 2.4%Si has the finest graphite distribution. This graphite cast steel has good machinability nearly equal to that of nodular graphite cast iron FCD45 as well as high rigidity nearly equal to conventional carbon steel. This cast steel is superior to nodular graphite cast iron with respect to fatigue strength and impact strength

超微細粒複合組織強化鋼の疲労特性

Fatigue strength and fatigue crack growth behaviors were studied for two types of dual phase steels with duplex ferrite and martensite structure: One was an ordinary dual phase steel processed to replace pearlite by martensite and another was a fine grained one obtained with the method developed by N. Matsumura and M. Tokizane. Major attention was paid to the fatigue properties of the fine grained dual phase steel.The results of this study revealed the fatigue characteristics as follows:(1) The fatigue strength of the dual phase steel, especially that of the fine grained one was excellent.(2) The crack propagation life to failure from the initiation of small crack with the length of 0.1mm was longer for the fine grained dual phase steel than the ordinary one, indicating that the former material has a higher resistance against the crack growth of short cracks.(3) The crack growth rate of long cracks for both materials was higher than those of the conventional structural carbon and alloy steels in the relatively low stress intensity region.

Hydrogen Induced Cracking Susceptibility of High-Strength Line Pipe Steels

Abstract The effects of chemical compositions, rolling conditions, and homogenization treatment on hydrogen induced cracking (HIC) have been studied metallurgically using laboratory heats of chemical compositions corresponding to those of the center segregation zones in continuous cast slabs. The hardness of the center segregation zones in steel plates is one of the predominant factors affecting the HIC susceptibility of high-strength line pipe steels. An increase of the carbon equivalent (Ceq) or phosphorus content hardens the center segregation zones in conventional carbon steels produced by the controlled rolling (CR) process. Lowering the carbon content to the range of 0.01 to 0.05% markedly decreases the hardness of center segregation zone and reduces the HIC susceptibility, regardless of the increases in other alloy elements. Hot rolling at relatively lower temperature increases the hardness of the center segregation zone and results in a slightly high HIC susceptibility. The design of the chemical ...

Ac magnetic characteristics of cores made from pressed, annealed, and repressed rectangular steel particles

This paper describes a material and new method of processing that yields pressed compacts magnetically suitable for a variety of ac applications. Small rectangular plain-carbon steel particles with dimensions 2.0×0.51×0.15 mm are decarburized, individually insulated and uniaxially pressed using typical powder-metallurgical techniques. In this condition the 60-Hz losses are somewhat higher than conventional carbon steel sheet while at higher frequencies the losses are lower. This loss behavior is due to the large hysteresis-to-eddy current ratio,>9. The permeability of the compacts is poorer than that of carbon steel sheet. Attempts to reduce the core loss by lowering the hysteresis loss component through a series of stress-relief annealing experiments resulted in exceptionally high losses. These high losses were attributed to large circulating eddy currents caused by local particle-to-particle sintering. Subsequent repressing, either uniaxial or cold isostatic, resulted in a dramatic reduction in the eddy current loss component and a total core loss superior to that of conventional carbon steel sheet. The variations in magnetic performance are related to the sample density, initial core pressing pressure, the annealing parameters, and the repressing method and pressure.

AC magnetic characteristics of cores made from pressed rectangular steel particles

This paper describes a new material and method of processing that yields pressed. compacts magnetically suitable for a variety of AC applications. Small rectangular plain-carbon steel particles ranging in size from 1.5 × 0.25 × 0.15 mm to 3.8 × 0.61 × 0.15 mm are decarburized, individually insulated and uniaxially pressed using typical powder metallurgical techniques. The magnetic properties of compacted ring specimens were measured. The AC losses and permeability of the pressed compacts are strongly dependent upon pressing pressure and particle geometry. Increased compact density lowers the iron losses. Variations of iron loss among the various particle geometries are caused by changes in particle shape anisotropy. At 60 Hz the losses are somewhat higher than those of Conventional carbon steel laminations while at higher frequencies the compact losses are lower. This loss trend is due to the small eddy current contribution to the loss. Permeability also depends upon compact density and particle geometry. Increased density not only lowers the induction within each particle for a fixed overall compact induction, but also decreases the magnetostatic energy within the compacts. Both effects result in the increase in permeability with increased density. The smaller the demagnetizing factor of the individual particles, the higher is the permeability. Iron loss and permeability respond differently to particle geometry; hence, selection of the best particle size will depend upon which of the two characteristics is most important for the particular magnetic circuit involved.

FROSTLINE

Abstract FROSTLINE is a fine-grain, columbium-treated carbon steel designed to be an economical solution to structural design requirements at cold temperatures. Available in plate thicknesses up to 6 inches, it offers high levels of toughness at temperatures to 80 F and higher strength levels than conventional carbon steels. Frostline also offers excellent welding characteristics, because of its low carbon equivalent. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as fracture toughness. It also includes information on forming, heat treating, and machining. Filing Code: CS-67. Producer or source: Lukens Steel Company.

Bending and torsion properites of endodontic instruments.

Abstract A torque meter and an improved testing method were used to determine the stiffness in bending, resistance to permanent bend, torsional stiffness, and maximum torsional deflection for conventional and standardized carbon steel and stainless steel root canal files and reamers. The bending and torsional properties showed a gradual increase in stiffness and decrease in resistance to permanent bend as size increased, indicating that a triangular instrument was considerably less stiff and more resistant to permanent bend and torsion than a corresponding square instrument. No differences were found in the stiffness properties of carbon steel and conventional stainless steel instruments, whereas the experimental stainless steel instruments were considerably less stiff because of their greater ductility. Considerable variation was found in torsional behavior of instruments at large angular deflections because of the variations in ductility of the material and the amount of work-hardening in the individual instruments. The greater ductility of the stainless steel files allowed greater maximum angular deflection than the corresponding carbon steel files, but no differences were noted in the reamers. In conclusion, it appears from the general similarity of bending and torsional stiffness and from the general improvement in maximum torsional deflection that the stainless steel instruments would be more advantageous for clinical use.

Sintered constructional materials

The authors consider the problems of producing sintered materials replacing conventional carbon and alloy steels, cast irons, and nonferrous metals; the requirements to be met by metal powders for the production of constructional parts; methods of manufacture of constructional components from iron-cast iron and carburized iron type materials; techniques for the production of constructional parts from chromium steels by the method of diffusional chromizing in solid filler materials or by adding ferrochromium, chromized iron powder, or Kh30 steel powder to the charge. A description is given of techniques for obtaining sintered wear-resistant steels with a heterogeneous structure.

On the Mechanism of the Erosion of Fire-Clay Bricks for Bottom Casting Caused by the Flow of Molten Steel, and the Cause of the Occurence of Aluminous Sand

To the author's knowledge there exists no established explanation on the mechanism of the erosion of the bricks used in the equipments of bottom casting for producing conventional carbon steel with basic open-hearth furnace, and also with converter. Moreover, while it is generally assumed that the occurence of aluminous sand is very likely due to the erosion of the bricks by molten steel, in particular to the reaction of the reducing SiO2 of fire-clay bricks by Mn of molten steel, whose concentration is closely related to the deoxidizing reaction, the effective method of preventing the sand has not been known.From the results of the previous investigations the author concluded that the erosion of the bricks is mainly due to the oxides of slaggy matter contained in flowing molten steel, and also the occurence of aluminous sand is likely due to another causes. This paper contains the results of the mathematical-theoretical as well as the experimental studies carried out to prove more clearly the author's conception.