Research Of Laser Package Welding For Preparing Welding Compound Layer

Hydraulic column plays the significant role in supporting and bearing the pressure of the coal seam.However,the harsh environment in the mine have seriously damaged the usage of hydraulic column,corroding the surface of the hydraulic column and making them unusable.Therefore,the surface of the column surface has to be treated before using.Traditional surface treatment methods are electroplating,electroless plating and laser cladding.However,the former method is easy to produce electroplating waste water,which contains heavy metal ions and all kinds of acid mist exhaust,seriously polluting environmental.And the manufacture of laser cladding alloy powder is costly and difficult,also it will increase the air suspended particles.So,in this paper,it puts forward a new method to deal with the pillar surface,by using laser welding instead of laser cladding,thin strip instead of powder.In this paper,based on 304 stainless steel and 27 SiMn steel as the research object,it carries on the single channel laser lap welding and multi-channel laser lap welding to research the weld solidification model,the influence of process parameters on weld appearance and the preparation of welding the wear resistance and corrosion resistance of compound layer.And then using Inconel 718 alloy instead of 304 stainless steel welding to prepare the welding compound layer,compared to the two welding compound layer with wear resistance and corrosion resistance,the results are as follows: the edge of the 304 stainless weld are columnar crystal,appear to weld the center is equiaxial crystal,the organization at room temperature are ferrite and austenite;the microstructure of 27 SiMn steel weld center is board strips martensite,heat affected zone are martensite and bainite.It obtains good metallurgical bonding by welding the two materials and the microstructure in weld transition zone are martensite and ferrite and austenite.The average microhardness of 304 stainless steel parent metal is about 178.1 HV and the weld hardness increase to 279.4 HV,the microhardness for 27 SiMn steel is about 260.1 HV and weld the average microhardness rise to 392.9 HV.In the condition of different laser power,welding speed,defocusing distances,it can obtain good-quality weld bead.With the increase of laser power,the bead penetration and bead width,but the waist width and waist depth have no obvious change.The average microhardness of weld seam increases with the laser power.With the increase of welding speed,the weld width and depth of molten decreases,and the influence of welding speed to fusion width change is close to linear equation.Under different welding speed,average microhardness of weld seam doesn’t change a lot.Under the condition of different defocusing distance,the weld seam are smooth and uniform density without cracks,subsidence and bite edge.The penetration depth and bead width firstly increase and then decreases with the change of defocusing distance,but it has little influence in waist depth and waist width.Also,the microhardness of the weld seam doesn’t change a lot.In the condition of different laser power,welding speed,defocusing distances and overlap rate,it can obtain good-quality welding composite layer.The abrasion loss is closely relatedly to the surface hardness.The greater the hardness value,the smaller the amount of abrasion loss.At the laser power of 400 W,welding speed of 0.8 m/min,defocusing of 0 mm and overlap rate of 60%,it respectively gets their minimum value.By analyzing the wear morphology,it is mainly adhesive wear.The corrosion performance was tested and compared with the 304 stainless steel base material,The corrosion resistance of the compound layer is slightly worse than that of that of 304 stainless steel.The surface hardness of Inconel 718 alloy and 27 SiMn steel was 1.74 times higher than that of the 304 stainless steel and 27 SiMn steel welded compound layer,and the wear performance was better than that of the 304 stainless steel and 27 SiMn steel welded compound layer.Corrosion resistance was slightly worse than that of 304 stainless steel and 27 SiMn steel welding compound layer.