Fracture toughness of CA6NM alloy,quenched and tempered,and of its welded joint without PWHT

CA6NM quenched and tempered steel is used in hydraulic turbine rotors, pumps and compressors. The objective of this research is to determine the fracture toughness of tempered and quenched CA6NM alloy, and of its welded joints without post-welded heat treatment (PWHT). To this end, compact tension (CT) test pieces are milled from pieces of CA6NM steel for evaluation of the toughness of the alloy used in a hydraulic turbine. Due to the elasto-plastic condition of the material, the test pieces are tested by means of the J integral concept, setting out the resistance curve J–R and the crack initiation J _IC. In welded joints produced from ingots, without PWHT, the fragility they show does not allow the J–R curve for the CT test pieces to be drawn up, and the toughness is characterized by means of the K _IC concept. The welding procedure looks at the probable conditions for repair of cavitation wear to the turbine, where PWHT cannot be carried out. The results confirmed the higher toughness for the CA6NM steel, with values approximately three times higher than those obtained in the welded joints without PWHT. In terms of the fracture, the CA6NM steel shows ductile behaviour while the welded joint without PWHT shows fragile behaviour.     

Comparison of the modified vest and the direct anastomosis for radical retropubic prostatectomy

OBJECTIVES: This retrospective study was undertaken to compare the efficacy of the Vest and direct vesicourethral anastomosis for radical prostatectomy. METHODS: Five hundred six patients who underwent consecutive radical prostatectomies at our institution were analyzed. Two hundred fifty-nine patients underwent vesicourethral anastomosis using the Vest technique and 247 underwent a direct suture anastomosis. The groups were analyzed relative to time until healing, the occurrence of anastomotic strictures, and the continence rate 1 year after surgery. RESULTS: Approximately twice as many patients who underwent the Vest procedure experienced delayed healing and 8.5% developed anastomotic strictures compared with 1.2% of the direct anastomosis group. The Vest group experienced slightly better urinary continence 1 year postoperatively. CONCLUSIONS: The Vest procedure is a reasonable alternative to direct anastomosis for radical prostatectomy and provides similar results. We suggest specific circumstances when the Vest anastomosis may be particularly useful.