Method of controlling the quality of seam welded product

Claim 1

A method of controlling the quality of a continuously produced thin wall tubular product having a longitudinally extending weld seam, said seam being formed by an electrically produced welding arc generated across confronting edges of product stock at a welding station during relative movement between said stock and station, and as said edges are urged together in abutting relationship by at least three squeeze rolls circumferentially spaced around said tubular product at a single location downstream of said welding station, the method comprising the steps of selecting the levels of weld parameters required to produce a weld seam of a desired high quality for welding said product, said weld parameters consisting of the pressure at which each of the three squeeze rolls individually urge the confronting edges of the stock together, the speed of the relative movement of the stock, eddy currents induced in the welded product, and three electrical parameters consisting of the grid current of an oscillator tube employed in a power source supplying the power requirements of the welding arc, and the voltage and current of rectifiers employed in said source, choosing upper and lower limits of deviation for the selected levels of said weld parameters at which the welded product will be considered as defectively welded if at least one of the deviations is beyond said selected limits, continuously supplying the electrical power requirements of the welding arc and continuously measuring the above three electrical parameters, continuously urging the confronting edges of the said stock together and continuously and individually measuring the respective pressures at which the three squeeze rolls urge the edges of said stock together, measuring the speed of the relative movement of said stock, continuously inducing eddy currents in the welded product and continuously measuring said eddy currents, monitoring the position of said stock between the locations at which the above measuring steps are made and a location at which the product is cut into lengths of a predetermined length, identifying for rejection said predetermined lengths of the product welded when any of the measurements of said weld parameters obtained by the previous measuring steps deviate from the limits chosen therefor, and Rejecting said predetermined lengths of product welded when the weld parameters deviate from the limits chosen therefor.

Claim 2

A method of controlling the quality of a continuously produced thin wall tubular product having a longitudinally extending weld seam, said seam being formed by an electrically produced welding arc generated across confronting edges of product stock at a welding station during relative movement between said stock and station, and as said edges are urged together in abutting relationship by at least three squeeze rolls circumferentially spaced around said tubular product at a single location downstream of said welding station, the method comprising the steps of selecting the levels of weld parameters required to produce a weld seam of a desired high quality for welding said product, said weld parameters consisting of the pressure at which each of the three squeeze rolls individually urge the confronting edges of the stock together, the speed of the relative movement of the stock, eddy currents induced in the welded product, and three electrical parameters consisting of the grid current of an oscillator tube employed in a power source supplying the power requirements of the welding arc, and the voltage and current of rectifiers employed in said source, choosing upper and lower limits of deviation for the selected levels of said weld parameters at which the welded product will be considered as defectively welded if at least one of the deviations is beyond said selected limits, continuously supplying the electrical power requirements of the welding arc and continuously measuring the above three electrical parameters, continuously urging the confronting edges of the said stock together and continuously and individually measuring the respective pressures at which the three squeeze rolls urge the edges of said stock together, measuring the speed of the relative movement of said stock, continuously inducing eddy currents in the welded product and continuously measuring said eddy currents, monitoring the position of said stock between the locations at which the above measuring steps are made and a location at which the product is cut into lengths of a predetermined length, identifying for rejection said predetermined lengths of the product welded when any of the measurements of said weld parameters obtained by the previous measuring steps deviate from the limits chosen therefor, and Rejecting said predetermined lengths of product welded when the weld parameters deviate from the limits chosen therefor.