The role of zirconium in microalloyed steels

Recently there has been a renewed interest in the addition of zirconium to microalloyed steels. It has been used since the early 1920's, but has never been universally employed, as have niobium, titanium or vanadium. The functions of zirconium in steelmaking are associated with a strong chemical affinity, in decreasing order, for oxygen, nitrogen, sulphur and carbon. Historically, the main use of additions of zirconium to steel was for combination preferentially with sulphur and so avoid the formation of manganese sulphide, known to have a deleterious influence of the impact toughness of wrought and welded steel. Modern steelmaking techniques have also raised the possibility that zirconium additions can reduce the austenite grain size and increase dispersion strengthening, due to precipitation of zirconium carbonitrides, or in high nitrogen vanadium-zirconium steels, vanadium nitride. This review gathers information on the compounds of zirconium identified in steels together with crystallographic data and solubility equations. Also brief accounts of the role of sulphides and particles in general on austenite grain size control and toughness are included

Genetic Polymorphisms in Venous Thrombosis and Pulmonary Embolism After Total Hip Arthroplasty: A Pilot Study

Deep venous thrombosis (DVT) after major orthopaedic surgery is a substantial concern. We asked whether the single or combined presence of thrombophilic genetic polymorphisms might further increase the already high risk for venous thrombosis and pulmonary embolism (PE) after THA. We therefore compared the prevalence of factor V Leiden, prothrombin G20210A, methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C, and plasminogen activator inhibitor 4G/5G polymorphisms between 50 patients with symptomatic DVT within 3 weeks after elective THA and an asymptomatic control group of 85 patients. We found no major difference for the presence of a single mutation between the groups. Factor V Leiden and homozygous MTHFR C667T mutations were of borderline significance with odds ratios (95% confidence intervals) of 3.73 (0.89–15.63) and 2.93 (0.92–9.29), respectively. Patients with homozygous or combined heterozygous status of MTHFR C677T and A1298C mutation had a higher frequency of DVT after elective THA (odds ratio, 2.86; 95% confidence interval, 1.32–6.35) than those with wild-type. The presence of a single mutation may not further increase the already high risk for symptomatic DVT after THA, whereas combinations of mutations of distinct polymorphisms might be important. However, prospective studies with a larger number of patients are needed before we would recommend preoperative screening