Factors affecting the final grain size of decarburized lamination steels

A study was made of the effects of carbon content, strain, initial grain size, carbide morphology, annealing time, and temperature on the final grain size produced after the decarburization anneal. The results show that columnar grains form only in higher carbon (0.05/0.06 Pct C) steels with low initial grain sizes (<20 μm) when decarburized at 1450 °F (788 °C). Equiaxed grains, however, are obtained in low carbon (0.02/0.03 Pct C) lamination steels for all processing conditions. It was found that the formation of both equiaxed and columnar final grain size (GS _f ) was dependent upon percent strain (ε), initial grain size (GS _i ), and carbide distribution (D _c ) according to the following regression equations (all grain size measurements in μm):G5 _f (columnar grain) = 204 + 0.9GS_i - 12.3ε + 37.8D _C logGS _f (equiaxed grain) = 2.151 + 0.022GS_i - 0.038ε - 0.0005GS _i · ε- 0.0002(GS _i )² + 0.079D _c A.R. Marder, formerly with the Research Department, Bethlehem Steel Corporation, Bethlehem, PA 18016 This paper is based on a presentation made at the symposium “Physical Metallurgy of Electrical Steels” held at the 1985 annual AIME meeting in New York on February 24–28, 1985, under the auspices of the TMS Ferrous Metallurgy Committee.     

Parameters affecting sag resistance in spring steels

Recent trends toward reducing the weight of automobile suspension springs have led to the development of a number of microalloyed steels and a variety of processing treatments which have claimed to improve the sag resistance of springs while increasing their operating stresses. More often than not, however, the subtle effects of varying levels of hardness and prior austenite grain size, as well as small but significant differences in critical elements such as Si, are over-looked in comparing these new steels with the conventional grades. Hysteresis loops measured in tension (related to the Bauschinger effect) were used to determine the relaxation behavior of a number of microalloyed and standard grade spring steels. The effects of hardness level, austenitizing temperature, prior austenite grain size, and warm prestressing on the Bauschinger hysteresis loops were also established. Silicon was found to be the most important factor influencing the size of the hysteresis loops; the greater the Si content of the steel (up to 2.2 pct), the larger the loops at a given strength level and the greater the expected relaxation resistance of the spring. The standard AISI 9261 steel containing 2.2 pct Si showed the same Bauschinger loops as the microalloyed grades containing Nb and V at the same hardness of 50 HRC.     

Delta-ferrite recovery structures in low-carbon steels

The development of delta-ferrite recovery substructures in low-carbon steels has been observed in-situ utilizing laser scanning confocal microscopy (LSCM). Well-developed sub-boundaries with interfacial energies much smaller than that of delta-ferrite grain boundaries formed following transformation from austenite to delta-ferrite on heating. It is proposed that transformation stresses associated with the austenite to delta-ferrite phase transformation generate dislocations that subsequently recover into sub-boundaries by a process of polygonization. Experimental evidence in support of this proposal was found in a ferritic stainless steel. Thermal cycling through the high-temperature delta-ferrite/austenite/delta-ferrite phase transformation leads to the development of a well-defined recovery substructure, which, in turn, modifies the low-temperature austenite decomposition product from Widmanstätten to polygonal ferrite, with a commensurate change in hardness.     

Factors influencing the machinability of sintered steels

The machinability of powder metallurgy materials is considered to be poor. The main factors that deteriorate the machining of PM parts are introduced in this work. They are those which participate in different ranges and modes in the formation of a sintered body with required mechanical and other characteristics. The effect of base iron powders, alloying systems, and alloying elements, as well as the effect of processing routes, especially solid-state sintering, are mentioned. The characteristic heterogeneous microstructures are presented. The effect of porosity in terms of interrupted and deformation cutting theories is discussed and demonstrated. The main measures to improve machinability of PM materials are described.     

Formation of pearlitic banded structures in ferritic-pearlitic steels

The conditions for ferrite and pearlite banding in strip and plate made of structural steels were investigated. Factors found to influence the formation of banded structures were the cooling rate during the γ/α-transformation, the former austenite grain size, and the work-hardened condition of the former austenite. Analyses with the aid of an electron beam microprobe made it possible to demonstrate that the carbon-rich bands correspond locally with banded manganese enrichments, yet that they do not form before the course of the γ/α-transformation as a result of secondary segregation. It was possible to explain the mechanism of action of the influencing factors on the basis of this model.     

Similarities between the martinsitic and cold-worked structures of steels

Abstract

Close analogies existing between the mechanical and physical properties of marten sitic and cold-worked steels are partly due to the high densities of dislocations in both structures. Therefore, a parallelism should exist between the mechanisms of tempering quenched steels and of annealing cold-worked steels.

Extra-low carbon steels permit this parallelism to be established. The three classical stages of tempering in high-carbon steels being negligible in extra-low carbon steels (1,2), the mechanism of tempering the latter steels is rather similar to the mechanism of annealing cold-worked structures and occurs essentially in two stages (3): a progressive restoration interpreted in terms of a rearrangement of dislocations, and a recrystallization responsible for eliminating the remaining ‘excess’ dislocations.

It will be shown that an age-hardening phenomenon interrupts these two stages. It will also be shown by transmission electron microscopy that the above interpretation of the two stages applies well to the tempering of extra-low-carbon steels.

Résumé

Il existe une grande analogie entre les propriétés des aciers martensitiques et celle des aciers écrouis. Si les défauts réticulaires des deux structures sont de même nature, il devrait aussi exister un parallélisme entre le mécanisme du revenu des aciers après trempe et celui du recuit après écrouissage.

On peut utiliser les aciers extra-doux pour établir ce parallélisme. On sait que les réactions hétérogènes observées lors du revenu des aciers à haute teneur en carbone sont négligeables dans de tels aciers (1,2) et que leur revenu, tout comme leur recuit, se déroule essentiellement en deux stades (3): une restoration proprement dit e durant laque lIe se produit un réarrangement des dislocations suivie d'une recristallisation complétant I'élimination des défauts introduits durant la transformation. Dans cette communication, nous montrerons que le premier stade du revenu est interrompu par un phénomène de vieillissement. De plus, l'interprétation précédente des deux stades du revenu après trempe dans le cas des aciers extra-doux sera confirmée par microscopie électronique.     

Factors affecting the biodegradation of toluene in soil

The biodegradation of toluene in soil microcosms was examined in order to identify the physical, chemical, and biological factors which determine the fate and lifetime of organic chemicals in soils. Toluene degradation rates were proportional to the initial substrate concentration and these rates reached a maximum at a concentration of 200 micrograms/g. No degradation occurred above this concentration presumably due to the toxicity of the hydrocarbon to the soil microorganisms. Small differences were observed in the degradation rates in soils at different moisture content. However, the availability of water in soil appeared to limit toluene degradation only at a very low water content. The lifetime of toluene in soil was also related to the initial level and activity of the soil microorganisms. Toluene was metabolized rapidly in those soils which initially contained high levels of degrading microorganisms. Furthermore, exposure of the soil to toluene resulted in an increase in the number of degrading organisms. The lack of inorganic nutrients such as nitrogen prevented complete degradation of toluene in a clay soil which contained high levels of degrading microorganisms. The biodegradation of organic chemicals in soil is not an intrinsic property of the molecule and cannot be predicted without first delineating the environment in which it is found. The biodegradation of a compound is defined by the biological, physical, and chemical characteristics of the soil environment. The lifetime of a chemical in soil results from a combination of all three of these parameters.     

Effect of cooling conditions and physical properties of alloys on dispersity of the dendritic structure of ingots and castings

It is established that an increase in the dendritic cell size in a steel structure compared with duralumin at identical solidification rates is associated with the lower thermal diffusivity and higher melting point of steel (increased tendency to supercooling). As the solidification rate increases, the dendritic cell size decreases because of the prevalent effect of a decrease in the crystallization time in the liquidus-solidus range compared with the effect of an increase in supercooling. A specific urgency of increasing the dispersity of the dendritic structure of alloys that combine a decreased thermal diffusivity with a high melting point is mentioned (steel, cast iron, nickel, nickel alloys).     

Factors affecting the outcome of foetal hydrocephaly

In this study, the authors attempt to provide an account of the factors that affect the outcome of hydrocephaly in 26 foetuses. The hydrocephalus was related to a myelomeningocele in 35% of patients. Sixty-two percent of foetuses showed intra-uterine progression of their hydrocephalus and 50% were shunted postnatally. At a mean follow up of 2 years, the outcome was considered "fair" in 54% of patients. Our findings demonstrate that in foetal hydrocephaly a more favourable outcome is expected in patients with hydrocephalus which does not progress in utero, in whom the labour is not induced before 36 weeks of gestation, who are delivered vaginally weighing more than 2.5 kg and have a head circumference below the 95th centile and a CT cortical mantle thickness of 2 cm and more and who are treated by CSF shunting. The diagnosis of the foetal hydrocephaly at or before 28 weeks of gestation and the presence of a myelomeningocele did not affect the outcome significantly. Neurosurgeons are reminded to keep an open mind for infants with foetal hydrocephaly and to offer active treatment to patients with a potentially favourable outcome.     

Factors affecting high-density lipoproteins

Although it is well established that a low-circulating level of high-density lipoprotein (HDL) cholesterol is strongly associated with the likelihood of developing atherosclerotic coronary heart disease (CHD), the causal nature of this association has not been shown. Low levels of HDL cholesterol frequently are associated with other CHD risk factors, whose correction, often by hygienic means, may reduce CHD risk with minimal risk of adverse side-effects. However, other recommended hygienic interventions may lower HDL cholesterol levels. Specific safe and effective drugs for correcting a low HDL cholesterol level are not available and the potential value of specific pharmacologic treatment of this condition in the treatment or prevention of CHD remains unproven. Thus, while HDL measurement should be incorporated routinely in risk-assessment, intervention efforts should focus primarily on lowering low-density lipoprotein cholesterol.     

Factors affecting the immobilization of metals in geopolymerized flyash

Geopolymerization, a fairly new technology based on a very old principle, has emerged during the last few years as a possible solution to some waste stabilization and solidification problems. Some commercial successes have been achieved, although the technique remains fairly unknown as well as seemingly unpopular. It has been shown that most waste materials containing sources of silica and alumina should be capable of taking part in a geopolymerization reaction. In this article, flyash was used as a reactant in creating a geopolymeric matrix for the immobilization of process water containing 25,000 ppm of Cu or Pb cations. By means of X-ray diffraction, scanning electron microscopy (SEM), infrared spectroscopy, Brunauer-Emmett-Teller (BET), compressive strength, as well as kinetic leaching analyses, the main factors influencing matrix stability, immobilization efficiency, and therefore leaching behavior were investigated and discussed qualitatively. It was found that relatively high strengths could be obtained using low Ca flyash. The environment and coordination number of source aluminum and silica seemed to play a major role in the eventual matrix stability. Other factors influencing matrix stability include the alkali metal cation used as well as the type of metal being immobilized. The kinetics of leaching of immobilized metals from the geopolymerized flyash were qualitatively found to proceed along a combination of pore diffusion and boundary diffusion control mechanisms. It is finally concluded that immobilization of metals in geopolymerized flyash proceeds by a combination of physical encapsulation and chemical bonding, with adsorption also thought to play a role.     

Factors influencing the strength differential of high strength steels

Room temperature tensile and compressive true stress-true strain curves of various high strength steels (quenched and tempered 4340 steel, 410 martensitic stainless steel, and H-11 steel; and aged 300-grade 18 Ni maraging steel) were analyzed to determine the effect of the various microstructures, on what has been termed the strength differential (SD),i.e., the strength level difference between the tensile and compressive flow curves. Care was taken to insure that the compressive deformation was homogeneous. Regardless of the amount of plastic deformation, the quenched and tempered steels exhibited a higher flow stress in homogeneous compressive deformation than for tensile deformation. The extent of the SD was dependent on tempering temperature. This observation is consistent with what others have observed regarding yield strength behavior of quenched and quenched-and-tempered steels. Despite the low carbon content, aged maraging steel also showed a greater resistance to homogeneous compressive deformation. Metallographic examination of the maraging steel revealed the banding that is indicative of segregation. However, homogenization had little effect on the SD despite a change in austenite grain size, reverted austenite content, and the austenite-to-martensite transformational strains shown by Goldberg to be present in segregated material.     

Factors affecting the shrinkage of fly ash geopolymers

The shrinkage of fly ash geopolymers was studied in the present study.Fly ash was used as the source material for making the geopolymers.The effects of the concentration of Na0H,sodium silicate-to-NaOH ratio,liquid-to-ash ratio,curing temperature,and curing time on shrinkage were investigated.The geopolymers were cured at 25,40,and 600C,respectively.The results indicate that the shrinkage of geopolymers is strongly dependent on curing temperature and liquid-to-ash ratio.The increase in shrinkage is associated with the low strength development of geopolymers.It is also found that NaOH concentration and sodium silicate-to-NaOH ratio also affect the shrinkage of geopolymers but to a lesser extent.     

Factors affecting the work efforts of disabled-worker beneficiaries

Congress is currently placing considerable emphasis on returning disabled-worker beneficiaries to work. However, going back to work is only the first step in the complex process of program termination due to work and trust fund savings. Not only must the beneficiary get a job, but also the work effort must be sustained at what is considered a substantial gainful activity (SGA) level by the disability program (so that an SGA termination will result) and a reasonable living condition must be achieved by the beneficiary (so that the person is motivated to continue working and lose benefits). This article focuses on those factors that affect the ability of the beneficiary to sustain such a work effort. Combined with previous findings about returning to work, we begin to see the overall effect of the factors on work efforts. Beneficiaries who have physical therapy rehabilitation have a higher tendency to start working and a lower tendency to stop. Those with vocational training or general education have a higher tendency to start working, but these factors do not help to sustain the effort. Beneficiaries who were helped with job placement have a higher tendency to start work, but they also have a higher tendency to stop. If beneficiaries knew about the trial-work period, but not about either the extended period of eligibility or Medicare continuation, then they had a higher tendency to start work and a higher tendency to stop. However, if they knew about all three work-incentive provisions, then the tendency to work was not affected.     

Factors affecting the mobility of pediatric dentistry faculty

A 66-year-old female underwent uneventful removal of parasagittal meningioma. At surgery, a piece of Biobond-soaked oxycellulose was applied to the lateral wall of the superior sagittal sinus for hemostasis. Her early postoperative course was complicated by focal but severe brain edema, which was adjacent to the hemostatic agent. Unlike foreign body granuloma previously reported, this complication was considered to be attributed to inflammatory reaction of Biobond, because of the early onset and fulminant edema despite of small volume of the mass lesion. Although there have been no previous reports of this complication, it should be kept in mind that intracranial application of Biobond may induce fulminant inflammatory reaction as seen in this patient.     

Factors affecting the self-concepts of South African students

Relationships among family macrosocial structures, proximate family settings, attributions of responsibility, and African adolescents' self-concepts were examined. Data were collected from 460 South African high school students (234 girls, 226 boys; mean age = 18.6 years). On the basis of partial least squares path modeling, the results suggest that (a) family macrosocial structure, proximate family settings, and the individual's sense of responsibility for academic outcomes had modest to strong associations with different dimensions of self-concept; and (b) there were gender-related differences in the structure of the adolescents' social status backgrounds and self-concepts and in the relationships among social status, perceptions of parents' support for learning, personal responsibility, and self-concept.