Laser cutting is that the horizontal laser beam emitted by the laser changes into a vertical downward laser beam through the 45° total reflector, and then focuses through the lens, forming a tiny spot at the focal point. When the spot hits the material, the material is heated to the vaporization temperature quickly, and evaporates to form a hole. With the movement of the beam on the material such as S420M steel plates, the auxiliary gas (carbon dioxide gas, oxygen, Nitrogen, etc.) blow away the melted slag, make the hole continuously form a very narrow width (such as about 0.1mm) cutting seam, and complete the cutting of materials.
S420M steel plates, S355JR is a European standard low alloy high strength structural steel, which is in accordance with EN10025-2. The hardness of S355JR steel is 70-80B, and the yield strength of S355JR steel is 355MPa. JR stands for quality level, equivalent to level B in ChinaChemical composition of S355JR steel: C: < 0.22; Si: < 0.55; Mn: < 1.60; P: < 0.025; S: < 0.025S355JR steel is equivalent to Q345B in China.
According to the data of the General Administration of Customs, in April 2020, China exported 6.311 million tons of S420M steel plates and so on steel, down 2.6% from March, down 0.3% year on year; from January to April, China exported 20.601 million tons of steel, down 11.7% year on year. In April, China imported 1.044 million tons of steel, down 11.70% from March; from January to April, China imported 4.184 million tons of steel, up 7.4% year on year.