Feasibility analysis and cutting process research on laser cutting medium-thick 20CrNiMo steel plates using a high-power fiber laser without assisted blowing

Rapid cutting of oil and gas wellhead tubing is the key to handling fire emergencies in oil and gas wells. However, it is difficult to perform close-range laser cutting on oil and gas wellhead tubing due to the impact of high temperatures on equipment. Therefore, it is necessary to conduct close-range laser cutting tests under unassisted blowing conditions to confirm the feasibility of long-distance laser cutting of oil and gas wellhead tubing. In this work, laser cutting experiments are conducted to analyze the feasibility of using a 10 kW high-power laser to cut medium-thick 20CrNiMo steel plates under unassisted blowing conditions. Firstly, the optimized cutting path, kerf width, cutting movement speed, and defocus amount for the 10 kW laser are obtained by unit cutting experiments on 20 mm thick 20CrNiMo steel plates under the condition of unassisted blowing. Secondly, a 10 kW laser source with preferable process parameters is used to cut the 50 mm thick 20CrNiMo steel plate. Qualitative and quantitative comparisons of kerf morphology and dimensions are used to evaluate the cutting quality. The results indicate that a wide kerf width with a top-down cutting path benefits the discharge of slag from the kerf under unassisted blowing conditions. Under the condition of fixed laser power, the cutting movement speed and the defocus amount affect the melting rate of metal materials, which in turn affects the cutting quality. This work confirms the feasibility of using a high-power laser with preferable process parameters to cut through medium-thick steel plates under the condition of unassisted blowing, which will help promote the application of the laser cutting technology in rescue situations such as oil and gas drilling fires and provide a reference for other industrial fields that need to conduct laser cutting experiments to medium-thick steel plates under unassisted blowing conditions.