Examination of weld defects by computed tomography

Defects in metal arc gas (MAG) welds made in S235JR low carbon steel of 6 mm thickness were examined. A sample containing lack of fusion (LOF) and pores was examined by computed tomography – CT. The computed tomography examination was performed in order to define LOF size and position as well as dimensions and distribution of accompanying pores in the weld metal

Ispitivanje grešaka zavara kompjutorskom tomografijom

Defects in metal arc gas (MAG) welds made in S235JR low carbon steel of 6 mm thickness were examined. A sample containing lack of fusion (LOF) and pores was examined by computed tomography – CT. The computed tomography examination was performed in order to define LOF size and position as well as dimensions and distribution of accompanying pores in the weld metal.Ispitivane su greške u zavarenom spoju niskougljičnog čelika S235JR debljine 6 mm zavarenog MAG postupkom. Uzorak koji sadrži greške naljepljivanja i pore je ispitivan kompjutorskom tomografijom - KT. Programskom analizom tomografa je određena veličina i pozicija grešaka naljepljivanja kao i dimenzije i raspored pratećih pora u zavarenom spoju

Ispitivanje grešaka zavara kompjutorskom tomografijom

Defects in metal arc gas (MAG) welds made in S235JR low carbon steel of 6 mm thickness were examined. A sample containing lack of fusion (LOF) and pores was examined by computed tomography – CT. The computed tomography examination was performed in order to define LOF size and position as well as dimensions and distribution of accompanying pores in the weld metal.Ispitivane su greške u zavarenom spoju niskougljičnog čelika S235JR debljine 6 mm zavarenog MAG postupkom. Uzorak koji sadrži greške naljepljivanja i pore je ispitivan kompjutorskom tomografijom - KT. Programskom analizom tomografa je određena veličina i pozicija grešaka naljepljivanja kao i dimenzije i raspored pratećih pora u zavarenom spoju

Fracture of drilling head pipe connection due to quenching of heat affected zone (HAZ)

The drilling head pipe connection is made of quenched and tempered steel 34CrNiMo6. The steel characteristic is high hardenability. Due to unsuitable and untested welding technology the heat affected zone (HAZ) cooling rate after welding surpassed the upper critical cooling rate. During horizontal drilling of the rock, the resulting brittle martensite could not bear the dynamic loads which led to a brittle fracture of the pipe connection

Identification of deep trap levels from thermally stimulated current spectra of semi-insulating CdZnTe detector material

Deep trap levels in the semi-insulating (SI) CdZnTe detector material were characterized by simultaneous multiple peak analysis based on thermally stimulated current (TSC) measurements. In our TSCs that have been published previously electron hole pairs were created through the use of proton beam irradiation. Charge carriers were captured in deep traps and afterward released by thermal emission, which was recorded in the 90–300 K range. We showed that the obtained TSC spectra could be well fitted with a unique set of 14 different deep traps, which were all simultaneously and completely characterized. The obtained trap data are in good accordance with earlier deep trap characterizations of the other authors obtained on similar SI CdZnTe materials using different methods

Identical and Nonidentical Twin Drugs

Dvojni lijekovi su lijekovi koji sadrže dvije farmakoforne skupine povezane kovalentnom vezom u jednu molekulu. Farmakoforne skupine mogu biti jednake (dvojni lijekovi s identičnim podjedinicama) ili različite (dvojni lijekovi s neidentičnim podjedinicama). Identični dvojni lijekovi mogu djelovati na receptore (receptori biogenih amina, peptidni receptori, Ca2+ kanali, σ-receptori u mozgu, leukotrienski B4-receptori), inhibirati razlieite enzime (enzimi HIV-a, protein-kinaze, prolil-hidrolaza, acil-CoA kolesterol aciltransferaza, spermidin-spermin-N1-acetiltransferaza, S-adenozilmetionin dekarboksilaza), te kao ligandi DNA. Neidentični dvojni lijekovi mogu djelovati na dva različita receptora, dva vezna mjesta na jednom receptoru, dva enzima ili na receptor i enzim.Twin drugs contain two pharmacophoric groups combined covalently in a single molecule. Pharmacophoric groups can be identical moieties (identical twin drugs) or different (nonidentical twin drugs). Identical twin drugs can act on receptors (biogenic amine receptors, peptide receptors, Ca2+ channel, σ receptors in the brain, leukotriene B4 receptors), as enzyme inhibitors (HIVenzyme, protein kinase, prolyl hydrolase, acyl-CoA cholesterol acyl transferase, spermidine- spermine-N1-acetyltransferase, S-adenosylmethionine decarboxylase), and as DNA ligands. Nonidentical twin drugs exert their dual action on two different receptors, on two binding sites of a single receptor, on two enzymes, or on both a receptor and an enzyme

Effect of nonmetallic inclusions on steel welds metal hot cracking

Intercrystally distributed nonmetallic inclusions greatly increase weld susceptibility to hot cracking. Oxide and sulphide inclusions are the result of contaminated base material or its highly oxidised surfaces and they can be a consequence of metallurgical reactions between welding slag and remelted base material, while carbide inclusions can occur due to the mixing of high-carbon base and low-carbon filler material. All welding surfaces must thus be cleaned before welding and the least possible mixture of base with filler material must be enusured during welding

Development of banded microstructure in 34CrNiMo6 steel

In this paper the development of a banded microstructure in hot-rolled 34CrNiMo6 steel which consisted of bainitic and martensitic bands is explained. The chemical compositions of the bands were measured with energy dispersive x-ray spectroscopy (EDS), which showed that the martensitic bands contained more alloying elements (Mn, Cr, Mo, Si) than bainitic bands. By using Oberhoffer reagent, the segregations of phosphorus were also revealed. These phosphorus segregations coincided with the positive segregations of the alloying elements. The continuous cooling transformation (CCT) diagrams of steel were calculated. They confirmed the formation of martensite in positive segregations and the formation of bainite in negative segregations

Structural and thermodynamic analysis of whiskers on the surface of grey cast iron

The paper focuses, first, on the characterization of the whiskers on the surface of grey cast iron and second, it gives an explanation of whiskers growth based on thermodynamic calculations. The whiskers were observed on the surface of hot plates for the electric stove after black-oxide-coating (blackening) performed the furnace at 650°C in order to produce a protective layer mainly of magnetite (Fe3O4). However, the whiskers caused brown spots on dark grey surface and thus, the surface was aesthetically damaged. The investigations confirmed that whiskers are of hematite (Fe2O3); however, the thermodynamic calculations present that hematite may be formed as a result of the oxidation of magnetite if the partial pressure of oxygen is increased during the blackening