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Rizhsky Politekhnichesky Institut

Vasily V Ardentov

Igor V Gorynin

Valery Pavlov

Jury F Balandin

Jury I Zvezdin

Viktor A Ignatov

Lev Y Gluskin

Vladimir V Zhitkov

Alexandr N Krasnov

Alexandr A Khokhlov

Rostislav K Melekhov

Eduard A Rokhlin

Alexandr G Ignatenko

Ivan A Stepanov

Alexandr F Anfimov

Inna S Osipova

Vladimir G Azbukin

Viktor M Burmakin

Viktor S Fastritsky

Viktor I Plotnikov

Jury B Florinsky

Laimonis T Vingris

Gennady N Alexeev

Leonid A Rodnevsky

A method of and apparatus for nondestructive testing of spot welds by producing in a test weld high and low frequency electromagnetic fields to induce eddy currents in the weld zone. The difference between the phase values of the resultant electromagnetic field intensities is indicative of the quality of the weld. The apparatus includes an eddy current transducer, high and low-frequency measuring channels, an indicator, and a controlled commutator for alternate connection of the eddy current transducer to the low-frequency measuring channel or to the high-frequency measuring channel. A memory unit is provided for storing the output signal of the high-frequency measuring channel, and a comparator is provided for comparing the signal stored in the memory unit with the output signal of the low-frequency measuring channel. A control unit alternately generates signals for simultaneously connecting the eddy current transducer to the high-frequency measuring channel and for storing the output signal of the high-frequency measuring channel in the memory unit, and signals for simultaneously connecting the eddy current transducer to the low-frequency measuring channel, and for comparing the signal of the low-frequency measuring channel with the signal stored in the memory unit.

Apparatus for non-destructive testing of spot welds using an

A corrosion-resistant weldable martensitic steel essentially consists of carbon 0.06 to 0.10 weight percent, chromium 15.1 to 16.5 weight percent, nickel 3.5 to 4.45 weight percent, silicon 0.10 to 0.60 weight percent, manganese 0.20 to 0.50 weight percent, at least one element selected from the group consisting of niobium 0.25 to 0.40 weight percent and zirconium 0.05 to 0.20 weight percent, at least one element selected from the group consisting of yttrium 0.05 to 0.20 weight percent, cerium 0.05 to 0.15 weight percent and lanthanum 0.05 to 0.15 weight percent, phosphorus not exceeding 0.025 weight percent, sulfur not exceeding 0.02 weight percent, copper not exceeding 0.20 weight percent, the remainder being substantially iron and unavoidable nonferrous impurities. The process for the manufacture of the steel comprises the steps of preparing a molten mass of said composition, pouring the molten mass into a mould and permitting it to solidify therein followed by cooling an ingot produced. The cooling step is carried out in at least two stages, the first stage residing in cooling the ingot to a temperature laying in martensite transformation start-end interval but not lower than to 100.degree. C., and then in its immediate heating up to tempering temperatures in the range from 600.degree. to 650.degree. C., whereas each subsequent stage comprises cooling the ingot to martensite transformation temperatures but by at least 50.degree. C. lower than the cooling temperature of the previous stage, thus bringing, with such a multistage cooling, the temperature of the ingot down to a value below the temperature of the end of martensite transformation, followed by final tempering in the temperature range of 600.degree. to 650.degree. C. and subsequent cooling to room temperature.

Corrosion-resistant weldable martensitic stainless steel, process for

Growing community of inventors

Saint-Petersburg, Russia

Vasily V Ardentov