Fatigue strength of 30ХГСА–40ХМФА welded joints produced by rotary friction welding

Rotary friction welding (RFW) is used in the production of drill pipes for solid mineral prospecting. The need creation lightened strings high-speed diamond drilling ultradeep wells dictates necessity a greater focus on study weld zone and setting RFW technological parameters. This paper presents results experimental studies welded joint pipe H standard size according to ISO 10097, made 30ХГСА (pipe body) 40ХМФА (tool joint) steels under cyclic loads. authors evaluated influence force applied workpieces process contacting surfaces (force during heating), postweld tempering at temperature 550 °С life joints, conditions alternate tension-compression cycle amplitude stress ±420 MPa. determined that with an increase heating, microstructure changes occur thermomechanical influence, contributing fatigue strength joints. identified negative effect which expressed decrease number cycles before failure by 15–40 %, depending magnitude heating. optimal mode specified combination determined, provides largest failure: heating (at friction) Fh=120 kN, forging Ffor=160 rotational frequency n=800 Rpm, upset l=8 mm. A series tests have been carried out various values produced steel base metal; limited endurance curves plotted. It shown differences body material (30ХГСА steel) are insignificant. obtained supplemented microhardness measurement data fractographs fractured samples, revealing mechanism crack propagation