A resistance spot welded joint of at least two steel sheets and a method of producing a resistance spot welded joint of at least two steel sheets, wherein at least one of the steel sheets is provided with a Zn containing layer, the steel sheet has a tensile strength of at least 980 MPa, a multiphase microstructure comprising bainite, bainitic ferrite and tempered martensite in a total amount of at least of 75 volume % and retained austenite in an amount of 3-20 volume % and wherein the steel sheet provided with the Zn containing layer has a composition consisting of (in wt. %): C 0.1-0.3; Si 0.2-3.0; Mn 1.0-3.0; Cr2.0; Mo0.5; Al2.0; Nb0.2; V0.2; Ti 0.01-0.15; B 0.0005-0.01; and balance Fe apart from impurities, wherein the heat affected zone in the spot welded joint is free from cracks having a length of more than 500 m.

A probe for an ultrasonic treatment tool is configured to transmit ultrasonic vibration to a biological tissue. The probe includes a substrate including a stainless steel, a structure of the stainless steel including one or both of troostite and sorbate.