The Research On Arc Control Method Of Ultra-narrow Gap Rail Welding

The national "13th Five-Year Plan" pointed out that our country will build new high-speed rail mileage of 11,000 km within five years,covering more than 80% of the cities to expand regional connectivity and promote national economic development.High speed railway requires high smoothness and high stability.In order to ensure the stability and smoothness of rail joints,it is essential to carry out seamless welding.There are some problems of the traditional method of seamless rail welding,such as complex equipments,huge investment,low joint strength etc.It is necessary to study of an efficient and high-quality in-situ seamless rail welding method.The ultra-narrow gap welding has the advantages of low heat input,narrow heat affected zone,small investment and high production efficiency.However,compared with other welding methods,the ultra-narrow gap welding is prone to the problem of arc climbing,poor root and sidewall fusion.The research group apply the ultra-narrow gap arc welding method to seamless welding of rails.In this paper,according to the characteristics of the ultra-narrow gap welding and the existing welding test data analysis,proposed an open loop control method suitable for the arc characteristics of the ultra-narrow gap welding,and developed arc control system for the ultra-narrow gap welding.This system designs an improved circuit for external characteristics of arc welding power source,which can change flat characteristic power source to falling characteristic power source with adjustable slope,in order to enhance the stability of the arc and solve the problem of "arc climbing";The arc voltage and current signal acquisition system based on Lab VIEW software and NI 6251-USB acquisition card is designed to facilitate the later analysis;A switching circuit is designed to meet the different requirements of voltage and current in arc ignition and normal welding stage;The motion control system is composed of SMC6490 four-axis motion controller,panasonic servo driver,servo motor and reducer.It can control the whole welding process accurately,ensure the stability of the welding process and improve the welding quality.In this paper,arc control method and the open loop control system for ultra-narrow gap arc welding are studied and developed.Through a great quantity ultra-narrow gap arc welding tests,the external characteristics of arc welding power suitable for ultra-narrow gap arc welding and the process specification applicable to this welding control system are found out.