Microstructure and toughness in high speed tool steels: the influence of hot reduction and austenitization temperature

Measurements of transverse rupture strength are reported for AISI M2, AISI M 35, AISI T 15 and ASP 30 produced by conventional ingot metallurgy, sintering of cold pressed powders, and hot rolling of HIP billets. Also reported are the size distributions of undissolved carbides and the effects of hot reduction and austenitization temperature on these and on the transverse rupture strength of test bars from the centre and the periphery of the bar stock, and of test bars oriented longitudinally and transversally to the rolling direction. Fracture initiating defects were identified and their size measured by SEM fractography. The results are discussed in terms of a fracture mechanical model for transverse rupture strength. It is inferred that in ingot-derived materials, fracture is initiated by micro-cracks formed by subcritical crack growth within the carbide stringers. In powder metallurgy materials, large carbides or carbide clusters initiate fracture. The model explains the dependence of transverse rupture strength on carbide distribution, degree of hot working, austenitization temperature, and specimen orientation. It is emphasized that transverse rupture strength is suitable for characterizing the defect population of a tool steel, but not the fracture resistance of small stressed volumes such as the cutting edge of a tool bit.     

The role of alloy composition in the precipitation behaviour of high speed steels

The role of alloy composition in determining the microstructure and microchemistry of a series of related high speed steels has been investigated by a combination of analytical electron microscopy and atom-probe field ion microscopy. The four steels which were investigated (M2, ASP 23, ASP 30 and ASP 60) cover a large range of C, V and Co contents. Excepting the Co content, the composition of primary MC and M₆C carbides and as-hardened martensite was similar in all four alloys and the major effect of increasing the content of C and V was to increase the volume fraction of MC primary carbides. Precipitation of proeutectoid carbides (mainly MC and M₂C) occurred during hardening of all four steels and the extent of this was greatest in the highly alloyed ASP 60. Tempering at 560°C resulted in the precipitation of extremely fine dispersions of MC and M₂C secondary carbides with very mixed compositions in all four steels. It was found that, as well as hindering the formation of autotempered M₃C in the as-hardened martensite, additions of Co refined the secondary carbide dispersion and delayed overaging reactions. Overaging at 600°C resulted in the precipitation of M₃C, M₆C and M₂₃C₆ at the expense of the fine MC and M₂C secondary carbide dispersion.     

Gold Medal Award for Life Achievement in the Practice of Psychology: Charles Silverstein.

The American Psychological Foundation (APF) Gold Medal Awards recognize distinguished and enduring records of accomplishment in four areas of psychology: the application of psychology, the practice of psychology, psychology in the public interest, and the science of psychology. The 2011 recipient of the Gold Medal Award for Life Achievement in the Practice of Psychology is Charles Silverstein. Dorothy W. Cantor, president of the APF, will present the APF Gold Medal Awards at the 119th Annual Convention of the American Psychological Association on August 5, 2011, at 4:00 p.m. Members of the 2011 APF Board of Trustees are Dorothy W. Cantor, president; William Howell, vice president/secretary; Gerald Koocher, treasurer; Elisabeth R. Straus, executive vice president/executive director; Norman Anderson; David H. Barlow, Camilla Benbow; Sharon Stephens Brehm; Charles L. Brewer; Connie Chan; Anthony Jackson; Ronald F. Levant; Sandra Shullman; Archie L. Turner; and Kurt Geisinger, APA Board of Directors liaison. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

On the crack susceptibility of high alloyed tool steels during continuous casting and in the temperature region of hot working

Hot tensile tests after applied prior melting down of the specimens were carried out on mainly ledeburitic tool steels and their strength and ductility were determined in the temperature range between liquidus and 900°C. The test parameters and specimen microstructures were adapted to the conditions and structures prevailing in continuous casting and primary hot working of blooms. The metallurgical processes leading to the embrittlement of the material were examined by means of metallographic investigations. The temperature ranges of internal crack susceptibility and low ductility were evaluated.     

基于ANSYS的高速磨削中的砂轮破坏原因的研究

应用可视化数值模拟方法,借助于大型通用有限元软件ANSYS建立砂轮回转的数学模型,对离心应力进行了仿真研究.随着磨削速度的提高,磨粒的切削作用被磨粒对工件的高速冲击作用所取代.通过输入不同的转速对比,发现砂轮孔壁处所受切向应力σt最大,径向应力很小可忽略,而在砂轮外圆处切向应力较小.随转速提高,外圆切向应力增长趋势显著,破坏趋势也愈明显,因此切向应力是破坏的主要原因.这一虚拟分析既为砂轮实际应用中出现的破坏现象所佐证,又与砂轮受力分析结果相吻合,为磨削过程的安全奠定了良好的基础.     

用高压变频器改造贵冶闪速炉排风机调速系统

分析了贵冶闪速炉排风机调速系统出现的问题 ,提出了用高压变频器改造其调速系统的方案 ,以及改造后的使用效果等。     

Interaction of the oxyfluoride melts of Ca,Si, Mg,Al, and Na with steels: II. Chromium-nickel-containing melts

The interaction of a mixture containing Ca, Si, Mg, Al, and Na oxides and fluorides with an ironbased chromium-nickel-containing melt at 1600°C and p _Ar = 0.1 MPa is studied. The equilibrium concentrations of the components in the slag are determined at a holding time of 500 s. The chromate capacity of this melt is calculated, and this value is related to the composition using the optical basicity.     

Research issues in cancer survivorship: report of a workshop sponsored by the Office of Cancer Survivorship, National Cancer Institute

We present the results of a prospective, randomised study comparing PBPC and BM focusing on engraftment, acute and chronic GVHD and survival. Forty patients with haematological malignancies received HLA-identical sibling BM (group A) or PBPC (group B). Evaluable patients were 19 (A) and 18 (B). Median age was 35 (17-56) in A and 29.5 (9-51) in B. Conditioning was mainly Bu-Cy2; GVHD prophylaxis was CSA-MTX. PBPC were harvested after 5 days of G-CSF 10 microg/kg/day. Median days for an ANC >0.5 x 10(9)/l was 18 (13-30) in A and 16 (11-25) in B (P = 0.10). Platelets >20 x 10(9)/l occurred at +17 (10-40) in A and +12 (9-36) in B (P = 0.01). The probability of > or =2 grade a-GVHD was 19% (A) and 27% (B) (P = 0.53). The probability of all grade c-GVHD was 70% with BM. In spite of the small number of patients in group B (PBPC), our data suggest the great majority of them will have c-GVHD (P = 0.08); extensive disease was present in 50 and 100%, respectively (P = 0.05). The estimates of overall survival for A and B at 1000 days are 51 and 47%, respectively (P = 0.67); DFS at 1000 days are 52 and 58%, respectively (P = 0.50). PBPC resulted in faster platelet engraftment. The incidence of acute and chronic GVHD was similar in both groups, but the severity of c-GVHD was higher with PBPC. No differences in survival and DFS have been observed to date.     

Stress corrosion cracking behaviour of stainless steels with respect to their use in architecture,part 2: corrosion in the passive state

Unexpected failures of 18/10 CrNi and 17/12/2 CrNiMo steels in indoor swimming pool atmospheres made it necessary to reinvestigate chloride stress corrosion cracking of stainless steels with respect to their use in arcitecture. A preceding paper presented inwestigations into stress corrosion cracking (SCC) in the active state of corrosion; the present paper deals with SCC In the passive state. The investigations showed that – in contrast to general opinion – stress corrosion cracking in the passive state can occur at temperatures well below 50°C in 18/10 CrNi and 17/12/2 CrNiMo steels, provided the corrosive medium has an extremely high chloride concentration. Other factors such as stress level, pH value or type of kation only exert a subordinate influence. Especially the high alloy austenitic steels 1.4439 and 1.4539 proved SCC-resistant under such conditions at ambient temperatures. Electrolytes with critical chloride concentrations may develop when deposits containing chlorides of sufficiently high solubility (e.g. MgCI₂, CaCl₂) are exposed to an atmoshere with critical, i.e. comparatively low humidity. Such conditions are evidently met only under very specific circumstances such as may occur in indoor swimming pools. In other structures where stainless steels have been used for decades without such damage having occurred to date, these critical conditions appear generally not to be reached.     

Stress corrosion cracking behaviour of stainless steels with respect to their use in architecture,part 1: corrosion in the active state

Unexpected failures on 18/8 CrNi and 17/12/2 CrNiMo steels in indoor swimming pool atmospheres made it necessary to reinvestigate chloride induced stress corrosion cracking (SCC). SCC in the active state was investigated on stainless steels 1.3974, 1.4301, 1.4303, 1.4439, 1.4462, 1.4522, 1.4539 and 1.4571 by testing under constant load at temperatures up to 50°C. Selected tests were performed on the material with the highest SCC susceptibility, 1.4301, in solutions with different concentrations of hydrochloric acid and sodium chloride. SCC was only observed in critical ranges of hydrogen-ion concentration and only in conjunction with pronounced general corrosion. In a solution with c(HCl) = 1.0 mol/l and c(NaCl) = 0.5 mol/l, which had proved to be highly SCC-inducing, the effects of different parameters on SCC behaviour were studied. Temperature, stress level and degree of cold deformation exerted only a secondary influence, in contrast to alloy composition: austenitic steels containing about 10% nickel (1.4301, 1.4303, 1.4571) exhibited very pronounced SCC. The other materials with nickel contents distinctively higher or lower proved, respectively, to be less susceptible or resistant to SCC. Thus, the same effect of nickel content was observed as is known for resistance to chloride induced SCC in the passive state. All materials were prone to pronounced general corrosion. The corrosion phenomena observed were completely different from the swimming pool failures reported.     

Studies on the determination of surface deuterium in AISI 1062, 4037, and 4140 steels by secondary ion mass spectrometry

The concentration of deuterium at the surface of cathodically charged high strength steels AISI 1062, 4037, and 4140 has been determined by secondary ion mass spectrometry (SIMS). The beneficial effects of pickling in NAP (a mixture of nitric, acetic, and phosphoric acids) to remove surfacebound deuterium have been observed. formerly with AMCA International Limited, Kanata, ON, Canada     

Learning and generalization of tool use by tufted capuchin monkeys (Cebus apella) in tasks involving three factors: Reward, tool, and hindrance.

We tested 4 captive tufted capuchin monkeys (Cebus apella) for their understanding of physical causality in variations of a 2-choice tool use task, 1 alternative of which allowed the monkeys easier access to food. Our monkeys, who had been adept at this task involving 2 items, that is, tool and food, quickly learned 3-term problems involving food, tool, and 1 type of hindrance (an obstacle or a trap, which could prevent success). All of the monkeys generalized their performance to new problems with the other type of hindrance and those with another familiar tool. These results suggest flexibility of their abilities to process complex physical information comprising 3 items in the environment, that is food–tool–hindrance spatial relationships. Such flexibility also implies that capuchin monkeys may possess rudimentary understanding of causal relationships involved in tool use. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developments in UK service provision for people with epilepsy: the impact of the NHS Executive Letter 95/120

The author describes the operating course of the Occupational Medicine Operating Units (OMOU) in our region. (Lombardia) These Units, born as a second level support to the Basal Occupational Medicine Units, greatly enlarged, as time passed, the limits of their users together with the charge of preventive duties ordered to the employers by the recent laws regarding Occupational Hygiene. (DLgs 277/91-DLgs 626/94) The author also illustrates the variety of the diagnostic demands to the OMOU according to the enlargement of the legal protection of occupational diseases and to the numerous aspects of specific job fitness. He underlines the need of multiple specialistic skillfulnesses achievable by means of a complete integration of OMOU in to the hospital to which they belong. In conclusion the author illustrates the new tasks of the OMOU in the field of the therapy and rehabilitation.