| Open arc surfacing welding technology can make the common metal material have special properties by coated with a layer of special material on the surface of common metal material, this technology can makes some common material have the special properties of some certain alloy compositions, this technology not only saves some rare metal resources, but also saves the cost for production and life, in the Fe-Cr-C system high chromium alloy welding products, often found some serious cracks in the surfacing layer, making the performance of the products so bad, and hindered the development process of this technology in the field of surface engineering.In order to solve this problem, this paper first proposed combining the mechanical stirring with the open arc surfacing welding technology, the research of this paper includes the. main characteristics of the organization of the layer that made by the composite-technology system, also the macrostructure,microstructure and properties of the welded surfacing layer are observed and analysed.Considering the distribution of carbide in the layer looks like nets, makes the layer by welding exists larger stress, in order to decrease the cracks resulted by larger stress in the cladding layer, through self modified equipment, while cladding on the Q235 steel surface by open arc welding with flux cored wire, the mechanical stirring was added in this method, after the experiment we obtained the more confusing macrostructure of carbide, reduced the number of cracks in the cladding layer, and the wear resistance is greatly improved.The experiment was divided into two steps:firstly, through scientific orthogonal experimental to explore a series of experimental parameters that fit this experimental environment, and then, combined with the welding parameters that explored by prior experiment, the mechanical stirring was added in this method.After completion of the experiment, by means of XRD, SEM, TEM, EDS and OM, analyized the phase composition of the cladding layer, observed the macrostructure and microstructure morphology in this layer.The use of Rockwell hardness tester, using three body abrasive wear testing machine and dynamic load abrasive wear testing machine measured the surface hardness of surfacing layer and wear properties. The results are as follows:l.The optimal welding parameters obtained by orthogonal experiment were:the welding voltage is 31 V, welding speed is 0.5 m·min-1, wire feeding speed is 6 m·min-1, when meet these parameters the three body abrasive resistance of the surfacing performance best.2.With welding parameters varied the microstructure of the surfacing layer are changed,when welding heat input is low the microstructure are acicular austenite and M7C3 carbides formed eutectic structure;when welding heat input is high the microstructure are:alloy austenite+carbide and austenite "Chrysanthemum" shape’s eutectic,its together constituted the hypoeutectic microstructure,and the carbides of the welding layer growth direction,but the austenitic distribution without direction, also in the carbides exists faults that parallel to the growth direction of austenite.3.When the weld pool applied rotary mechanical agitation,compared to the same length in the surfacing layer that without mechanical stirring, its smooth and surface crack volume reduced by 80%.At this time the microstructure of surfacing layer is:primary austenite+eutectic structure that constituted by austenite and flake (Fe,Cr)7C3 carbide that together constituted the hypoeutectic microstructure.This "Chrysanthemum" shape’s eutectic affected by the distribution of network austenite.4.When the weld pool applied rotary mechanical agitation, compared to the surfacing layer that without mechanical stirring,the hardness was 18.8% higher and impact abrasive wear properties increased 2 times;with increase of stirring speed,the surfacing layer of impact abrasive wear performance increased first and then decreased. |
PDF Full Text Request