טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentZak Anton
SubjectEffect of Laser Welding Parameters on Properties of
Maraging Steel 250 Welded Joint
DepartmentDepartment of Mechanical Engineering
Supervisors Professor Reuven Katz
Dr. Amiram Leitner
Dr. Amnon Shirizly
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

Laser beam welding (LBW) of Maraging steel 250 is a reliable and robust technique for welding special mechanical joints. Laser welding technique is characterized by a high density heat input, which minimizes the overall heat input into the joint. The LBW process enables penetration depth of up to 10 mm, low distortion, and low residual stress.

Laser welding technique is applicable for welding in the presence of heat sensitive components (such as electronic components). In order to ensure that no damage is caused to these components, temperature measurements should be conducted during the welding. Validated analytical and numerical heat transfer models of laser welding processes can be used to design the process and can replace the measurements.

The first part of the study is focused on predicting temperature distribution in a work piece during laser welding of Maraging steel 250. The prediction process includes calibration and validation of numerical and analytical models available in the literature. Commercial simulation software was used in the numerical process. These models were applied in an extensive experimental work that included temperature measurements during the laser welding process and showed good agreement between measured and calculated temperatures.

Many parameters affect joint quality of LBW welds. In order to meet design requirements, welding technologists must conduct numerous welding experiments to make sure that welding parameters are robust. In the second part of the current study, 6 technique was applied in order to shorten and systemize the parameterization process. To optimize the welding process, all parameters were considered, and only the significant parameters and their combinations were chosen. The 6 technique enabled minimization of the number of welding experiments. This procedure allowed development of a model that predicts joint properties per given set of input parameters.

During the experimental study, LBW experiments were performed upon Maraging steel 250 work pieces using a 4-kW Nd-Yag, solid state laser. The influences of the following parameters were tested: laser power, welding velocity, focal depth, focal radius, shielding gas angle, and cleaning technique. The effect of the above parameters on the penetration depth, welding width, and weld porosity were measured, compared, and validated with author-developed linear and quadratic models.