Powder surface welding method

Claim 1

A method for surfacing an engine valve with a surfacing powder by means of a plasma torch comprising supplying a plasma working gas from a space between a bar electrode and an inner tube surrounding the bar electrode and supplying a surfacing powder from a space between the inner tube and an outer tube surrounding the inner tube to a jetting nozzle to form a plasma arc while rotating the engine valve, wherein said surfacing powder contains not less than 95 percent of powder having a particle size of -60 mesh to +250 mesh, and the surfacing is carried out at a relative surfacing speed of not less than 3.8 mm/sec. and wherein a distance L (mm) between the end of said plasma arc jetting nozzle and said engine valve is within a range of 9.5Ds+6≦L≦Ds+8 (wherein Ds is an opening diameter (mm) of the plasma arc jetting nozzle) and an offset angle (θ) of the axial center of said plasma torch with respect to the rotational center of said engine valve is within a range of 7°≦0≦20° at a delay angle side.

Claim 2

A method for surfacing an engine valve with a surfacing powder by means of a plasma torch comprising supplying a plasma working gas from a space between a bar electrode and an inner tube surrounding the bar electrode and supplying a surfacing powder from a space between the inner tube and an outer tube surrounding the inner tube to a jetting nozzle to form a plasma arc while rotating the engine valve, wherein said surfacing powder contains not less than 95 percent of powder having a particle size of -60 mesh to +250 mesh, and the surfacing is carried out at a relative surfacing speed of not less than 3.8 mm/sec. and wherein a distance L (mm) between the end of said plasma arc jetting nozzle and said engine valve is within a range of 9.5Ds+6≦L≦Ds+8 (wherein Ds is an opening diameter (mm) of the plasma arc jetting nozzle) and an offset angle (θ) of the axial center of said plasma torch with respect to the rotational center of said engine valve is within a range of 7°≦0≦20° at a delay angle side.

Claim 14

An apparatus for surfacing an engine valve with a surfacing powder by means of a plasm a torch comprising a bar electrode, an inner tube surrounding the bar electrode to define a passage for a plasma working gas, an outer tube surrounding the inner tube to define a passage for a surfacing powder, a plasma arc jetting nozzle at the end of said outer tube for emitting a plasma arc toward said engine valve, a flow regulating member provided with plural holes for passing the plasma working gas and disposed between said bar electrode and said inner tube, means defining a shield gas passage outside said outer tube surrounding the plasma arc jetting nozzle, and an annular flow regulating member for the shield gas disposed in said shield gas passage adjacent to but spaced from the lower end of the outer tube wherein said plasma torch satisfies the following relationships Dr=(0.6˜0.9)×Ds, Tr=(0.9˜1.1)×Dr, De≦0.9×Dr in which Dr is an opening diameter (mm) of a plasma arc restraining nozzle formed in the end of the inner tube, Ds is an opening diameter (mm) of the plasma arc jetting nozzle, Tr is a nozzle thickness (mm) of the plasma arc restrainng nozzle, and De is a diameter (mm) of the bar electrode.

Claim 15

An apparatus for surfacing an engine valve with a surfacing powder by means of a plasm a torch comprising a bar electrode, an inner tube surrounding the bar electrode to define a passage for a plasma working gas, an outer tube surrounding the inner tube to define a passage for a surfacing powder, a plasma arc jetting nozzle at the end of said outer tube for emitting a plasma arc toward said engine valve, a flow regulating member provided with plural holes for passing the plasma working gas and disposed between said bar electrode and said inner tube, means defining a shield gas passage outside said outer tube surrounding the plasma arc jetting nozzle, and an annular flow regulating member for the shield gas disposed in said shield gas passage adjacent to but spaced from the lower end of the outer tube wherein said plasma torch satisfies the following relationships Dr=(0.6˜0.9)×Ds, Tr=(0.9˜1.1)×Dr, De≦0.9×Dr in which Dr is an opening diameter (mm) of a plasma arc restraining nozzle formed in the end of the inner tube, Ds is an opening diameter (mm) of the plasma arc jetting nozzle, Tr is a nozzle thickness (mm) of the plasma arc restrainng nozzle, and De is a diameter (mm) of the bar electrode.