Experimental study of cooling speed for ultra-thick steel plate during the jet impinging and quenching process

The quenching temperature drop curve for Q345B steel plate with 84 mm and 170 mm thickness was tested to analyze the distributing regularities and influencing factors of cooling speed for ultra-thick steel plate during the jet impinging and quenching process. The influences for temperature drop, temperature gradient and cooling speed were analyzed under the conditions of 60~100 m3/h water amount, 0.4~1.0 MPa water pressure, transient switching of quenching mode and the distribution of heat exchanger. Threedimensional heat anti transfer model, surface heat transfer coefficient model and thermal physical parameter model were built up by finite element and optimization. The results showed that the deviation of calculated and measured values was less than 4% for temperature drop curve model. The cooling speed of vertical section for 84 mm-thick steel plate was approximately proportional to surface heat transfer coefficient. The influence of surface heat transfer to cooling speed became weak when the thickness was increased. The influences of temperature effect when switching different quenching modes and temperature gradient of vertical section to cooling speed were stronger. The minimum value of cooling speed was about 1.0~1.8°C/s, between H/6 and H/3 region. These data provide the key information for increasing the cooling speed and uniformity.