Manufacturing method of tailored blank and manufacturing method of automobile part

1 . A manufacturing method of a tailored blank including a first steel plate and a second steel plate to be joined by butt welding, the method comprising butt welding the first steel plate and the second steel plate with a laser beam,

the laser beam comprising, on a beam radiating surface, a first region located in a central portion, a second region surrounding the first region, a third region surrounding the second region, and a fourth region surrounding the third region, and

the laser beam having a power density q1 in the first region, a power density q2 in the second region, a power density q3 in the third region, and a power density q4 in the fourth region, and the power density q1, the power density q2, the power density q3, and the power density q4 satisfying a relationship of q1>q2>q3>q4,

wherein a straight line direction extends perpendicular to the laser beam and passes through a center of the laser beam;

wherein each of the second region, the third region, and the fourth region has a corresponding inner boundary line, has a corresponding outer boundary line, and has a width extending between the corresponding inner boundary line and the corresponding outer boundary line;

wherein each of the second region, the third region, and the fourth region has a width the same as a width of the first region in the straight line direction;

wherein the laser beam is radiated at a total output power P1 in the first region, a total output power P2 in the second region, a total output power P3 in the third region, and a total output power P4 in the fourth region; and

wherein the total output power P1, the total output power P2, the total output power P3, and the total output power P4 satisfy a relationship of P1>P2 and a relationship of P1<P3, P4.

2 . The method according to claim 1 , wherein the first steel plate has a thickness different from a thickness of the second steel plate.

3 . A manufacturing method of a tailored blank including a first steel plate and a second steel plate to be joined by butt welding, the method comprising butt welding the first steel plate and the second steel plate with a laser beam,

the laser beam comprising, on a beam radiating surface, a first region located in a central portion, a second region surrounding the first region, a third region surrounding the second region, and a fourth region surrounding the third region, and

the laser beam having a power density q1 in the first region, a power density q2 in the second region, a power density q3 in the third region, and a power density q4 in the fourth region, and the power density q1, the power density q2, the power density q3, and the power density q4 satisfying a relationship of q1>q2>q3>q4,

wherein a straight line direction extends perpendicular to the laser beam and passes through a center of the laser beam;

wherein each of the second region, the third region, and the fourth region has a corresponding inner boundary line, has a corresponding outer boundary line, and has a width extending between the corresponding inner boundary line and the corresponding outer boundary line;

wherein each of the second region, the third region, and the fourth region has a width the same as a width of the first region in the straight line direction;

wherein the laser beam is radiated at a total output power P1 in the first region, a total output power P2 in the second region, a total output power P3 in the third region, and a total output power P4 in the fourth region, and

wherein a difference between a ratio of the total output power P3 to the total output power P1 and a ratio of the total output power P4 to the total output power P1 is 2.6 or less.

4 . A manufacturing method of an automobile part to be produced by forming of a tailored blank,

the tailored blank being produced by a manufacturing method of a tailored blank including a first steel plate and a second steel plate to be joined by butt welding, the method comprising butt welding the first steel plate and the second steel plate with a laser beam,

the laser beam comprising, on a beam radiating surface, a first region located in a central portion, a second region surrounding the first region, a third region surrounding the second region, and a fourth region surrounding the third region, and

the laser beam having a power density q1 in the first region, a power density q2 in the second region, a power density q3 in the third region, and a power density q4 in the fourth region, and the power density q1, the power density q2, the power density q3, and the power density q4 satisfying a relationship of q1>q2>q3>q4,

wherein a straight line direction extends perpendicular to the laser beam and passes through a center of the laser beam;

wherein each of the second region, the third region, and the fourth region has a corresponding inner boundary line, has a corresponding outer boundary line, and has a width extending between the corresponding inner boundary line and the corresponding outer boundary line;

wherein each of the second region, the third region, and the fourth region has a width the same as a width of the first region in the straight line direction;

wherein the laser beam is radiated at a total output power P1 in the first region, a total output power P2 in the second region, a total output power P3 in the third region, and a total output power P4 in the fourth region; and

wherein the total output power P1, the total output power P2, the total output power P3, and the total output power P4 satisfy a relationship of P1>P2 and a relationship of P1<P3, P4.

5 . The manufacturing method of a tailored blank according to claim 1 , wherein a sum of each of the widths of the first region, the second region, the third region, and the fourth region is greater than five times a minimum gap between the first steel plate and the second steel plate.