Method and apparatus for flash butt welding railway rails

• US 5,270,514 A
• Filed: 01/08/1992
• Issued: 12/14/1993
• Est. Priority Date: 01/08/1992
• Status: Expired due to Term

• Current Assignee: Progress Rail Welding Corp. (Caterpillar Incorporated)
• Original Assignee: Progress Rail Welding Corp. (Caterpillar Incorporated)
• Inventors: Battisti, Charles R., Wechselberger, Emmerich E.
• Primary Examiner(s): Shaw, Clifford C.
• Application Number:
  US07/817,910
• Time in Patent Office: 706 Days
• Field of Search: 219/97, 219/100, 219/101, 219/104, 219/55
• US Class Current: 219/100
• CPC Class Codes: B23K 11/046 Apparatus therefor
• CPC Class Codes: B23K 11/252 using digital means
• CPC Class Codes: E01B 29/42 Undetachably joining or fastening track components in or on the track, e.g. by welding, by gluing; Pre-assembling track components by gluing; Sealing joints with filling components E01B31/26 takes precedence; independent heating means E01B31/18; welding in general B23K; gluing metal parts in general F16B11/00

Abstract

A welding method and apparatus for flash butt welding adjacent ends of axially aligned railway rails includes a base frame and fixed and movable platens supported on the base frame. The platens support rail sections and are under the control of controller means operative to automatically move the movable platen through a predetermined distance/velocity relation as electrical power is inputted into the rail ends during straight flashing, preheating, flashing and upsetting phases of a welding cycle. The controller includes PID feedback loops operative to maintain the predetermined platen distance/velocity relation with entry of a single parameter by the operator. Significantly improved quality and repeatability of rail welds are obtained.

Claims

1. A method for straight flashing adjacent ends of a pair of railway rails to prepare the adjacent rail ends for weld joining, said method comprising the steps of;

securing the rails in generally longitudinally aligned relation for relative longitudinal movement therebetween,

applying electrical power to said adjacent rail ends while simultaneously effecting relative closing movement between said rail ends through actuating means so as to bring said rail ends into position to effect current flow between the rail ends, and

causing a feedback signal to be applied to said actuating means to automatically vary the rate of relative movement between said rail ends proportional to the current flow between said rail ends and in a manner to maintain a predetermined distance/velocity relative between said rail ends when moved relative to each other.

2. The method as defined in claim 1 wherein said actuating means is controlled by a proportional integral derivative feedback control loop operative to effect relative high velocity movement between said adjacent rail ends toward each other until said current flow between said rail ends is effected.

3. The method of claim 2 wherein said control loop is operative to reverse the relative movement between said rails when current flow between said rail ends is first detected, said control loop being further operative to establish a straight flashing distance limit in response to said first detection of current flow between said rail ends.

4. The method of claim 3 wherein said control loop is operative to effect a slow initial velocity between said rail ends until said current flow is detected, and effect a progressively increasing relative velocity between said rail ends toward each other during said straight flashing cycle.

5. The method of claim 4 wherein said control loop is operative to effect said progressively increasing relative velocity between said rail ends in response to a feedback signal proportional to the current flow between said rail ends during straight flashing.

6. A method for preparing adjacent ends of elongated railroad rails for flash butt-welding said adjacent ends, said rails having generally similar transverse cross-sectional configurations and similar metallurgical compositions, said method comprising the steps of;

positioning said rails in predetermined generally axially aligned relation so that end faces of the rails to be welded together are in mutually opposed spaced relation and are movable relative to each other to selectively vary the distance therebetween,

applying electrical power to the rails adjacent their mutually opposed end faces and simultaneously moving said adjacent end faces toward each other at a relatively slow velocity while monitoring electrical current flow between said opposed end faces, and stopping said relative movement of said rails toward each other when a current flow is detected between said end faces,

determining the positions of said adjacent rail ends at the moment of said current flow in relation to their range of relative longitudinal movement,

applying a signal to a process controller representative of the relative positions of said rail ends when said initial current flow is detected, said process controller being operative to establish a straight flashing distance for traverse by said rail ends,

moving said rail ends away from each other immediately after said current flow is detected until no electrical flow is detected between said end faces, and

thereafter effecting automatic relative movement of said rail ends toward each other under the control of said process controller in accordance with a predetermined distance/velocity relation while effecting current flashing therebetween until said rail ends have traversed said straight flashing distance toward each other.

7. A system for flash butt-welding adjacent ends of generally elongated railway rails having substantially similar transverse cross-sectional configurations and metallurgical compositions, said system comprising, in combination;

first support means for fixedly supporting a first one of said rails,

second support means for supporting the other of said rails such that an end surface thereof is mutually opposed to an end surface on said first rail and is movable relative thereof, and

controller means for effecting movement of said rail end surfaces toward each other in accordance with a predetermined distance/velocity relation determined by the rail cross-section and chemistry, said controller means being operative in response to feedback signals corresponding to the relative positions of said rails to apply a predetermined amount of electrical power to said rail ends sufficient to effect straight flashing and preheating of said rail ends.

8. A method for butt welding adjacent ends of a pair of railway rails supported in axially aligned relation, at least one of the rails being supported on a movable platen having means associated therewith for moving the corresponding rail longitudinally at a controlled velocity relative to the other rail so as to selectively adjust the spacing between the adjacent rail ends, said method comprising the steps of;

(a) straight flashing the adjacent ends of the rails to create substantially planar mutually opposed end surfaces,

(b) preheating said adjacent end surfaces by applying intermittent electrical power pulses to said end surfaces,

(c) final flashing said adjacent end surfaces in a manner to eliminate oxide inclusions and craters therein, and

(d) forging said opposed end surfaces together under a predetermined pressure to the point of refusal,

said steps of straight flashing and preheating including applying a predetermined total electrical power to the opposed end surfaces by controller means, said controller means being operative to apply a first portion of said predetermined power during straight flashing and apply the remainder of said power to said ends in intermittent pulses during said preheating, said controller being operative to initially divide said remainder power into a predetermined number of substantially equal power pulses and apply a first of said pulses to said rail ends, said controller means being further operative to sum the power actually applied during said first pulse, subtract said actually applied power from said remainder power to create a second remainder power, divide said second remainder power by the remaining of said predetermined pulses to establish a substantially equal number of remainder power pulses, apply a first of said remainder power pulses to said adjacent rail ends, sum the actual power applied during said first remainder pulse and subtract it from said second remainder power to establish a third remainder power, divide said third remainder power by the remainder of predetermined pulses to establish a substantially equal number of further remainder pulse, apply a first of said further remainder pulses to said rail ends, sum the actual power applied during said first further remainder pulses and subtract it from said third remainder power to establish a fourth remainder power, and continue summing the actual power applied to said rail ends during each successive power pulse, subtract it from the remainder of said predetermined power to be applied, divide the balance by the remainder of said predetermined pulses, and apply the quotient power to the rail ends for a predetermined period of time, until all of said remainder power has been applied to said rail ends during said predetermined preheat pulses.

9. The method as defined in claim 8, wherein said controller means is operative to automatically space said adjacent rail ends an initial predetermined distance apart, and effect relative movement of said rail ends toward each other in accordance with a predetermined distance/velocity relation so as to apply a predetermined electrical power to said ends as they traverse said predetermined distance substantially in accordance with said distance/velocity relation.

10. The method as defined in claim 9 wherein said controller means includes a proportional integral and derivative feedback control operative to control said straight flashing and preheat steps.

11. The method as defined in claim 9 wherein said controller means is operative to effect contact between said adjacent rail ends during each of said preheat pulses, and separate said rail ends at the end of each pulse.

12. The method as defined in claim 8 wherein said adjacent rail ends are spaced apart with substantially zero current flow therebetween after the last of said preheat pulses, said step of final flashing said adjacent end surfaces including effecting relative movement of said adjacent end surfaces toward each other at a relatively high velocity until current flow is established between said end surfaces, and determining the distance between said adjacent end surfaces when said current flow is established therebetween, said controller means being operative to effect predetermined relative movement between said adjacent rail ends in accordance with a predetermined closed loop equation.

13. The method of claim 12 wherein said controller means is operative in response to current flow between said adjacent end surfaces during final flashing to establish relative movement between said end surfaces in accordance with a predetermined flashing-distance platen-velocity relation.

14. The method of claim 13 wherein said controller means is operative to effect relatively slow movement of said adjacent end surfaces toward each other during initiation of said final flashing step, and thereafter effecting progressively increasing velocity closing of said end surfaces.