Patent ID: 6188037
Filing Date: 2001-02-13
Classification: B23K,C22C

Abstract:
A welded high-strength steel structure comprising a base metal and a weld metal, wherein the base metal is a steel whose microstructure is substantially formed of a mixed structure of martensite and lower bainite and which has a tensile strength of not less than 900 MPa; and the weld metal is a steel which comprises the following alloy elements based on % by weight:C: 0.01% to 0.15%;Si: 0.02% to 0.6%;Mn: 0.6% to 3%;Al: 0.004% to 0.08%;Ti: 0.003% to 0.03%;O (oxygen): not greater than 0.06%B: 0.0002% to 0.005%;Cu: 0% to 1.2%;Ni: 0% to 3%;Cr: 0% to 1.2%;Mo: 0% to 1%;V: 0% to 0.05%; andNb: 0% to 0.05%,and which satisfies the equations 1) and 2) below:0.25.ltoreq.Pcm .ltoreq.0.32Pcm =C+(Si/30)+(Mn/20)+(Ni/60)+(Cu/20) +(Cr/20)+(Mo/15)+(V/10)+5B 1)0.6.ltoreq.Al/O (oxygen) .ltoreq.1.4 2)wherein each atomic symbol in equations 1) and 2) represents its content (wt. %) within the steel.