Seamless Orbital Welding Heat Treatment

In order to meet the needs of the development of my country's railway transportation, while developing towards heavy load and full-length quenching, long seamless rails must improve their strength and toughness to improve the rail's resistance to wear, collapse, spalling and fatigue. and impact resistance to extend its service life, but most orbital welding factories cannot use it due to conditions. Let’s talk about seamless orbital welding heat treatment.

1. One of the reasons why rails are welded to seamless rails is:

(1) There is no gap between the tracks so that there will be no friction when the train is running.

(2) Reduce the difficulty for enterprises to lay and track.

(3) Reduce the number of collisions between a wheel and the rail and reduce carriage damage caused by resonance technology.

(4) Extending the collision interval between the wheels and the track can improve the safe speed of train operation.

2. Rail welding defects

2.1 Broken due to poor track welding contact

Poor contact welding often results in incomplete welding of the rail weld end surface, and forms a local melted surface and unmelted area in the drive rail where the weld is brittle and fractured.

2.2 Bad behavior of thermite welding causes rail breakage in my country

Thermite welding is a thermite smelting process that produces a casting structure that often suffers from various casting defects that are often repeated by local trains.

2.3 Failure of gas welding will cause rail breakage

Bad gas pressure welding behavior often easily causes light spots and fractures that affect the rail. Light spots refer to technical defects that fail to weld, and the fracture is silver-gray. Due to different bad air pressure welding environments, the residual stress of the rail changes greatly, especially at the waist. There is some residual tensile stress in the weld. This tensile stress occurs during the driving management process and is superimposed with the operating temperature stress generated by the train. When its strength is exceeded, the rail will break in an "S" shape along the waist.

3. Railway track welding quality management requirements for rails

The main demands for railways from high-speed railways include:

3.1 For track cross-section, most countries use 50kg/m or 60kg/m flat-bottom rails with lengths of 25m, 36m, 50m or welded long rails respectively.

3.2 Steel generally uses carbon steel, and its strength requirement is above 900MPa. In order to prevent the occurrence of fatigue and peeling in China's early stage, rail steel is required to be silicon-deoxidized killed steel, and the aluminum content in the steel is generally not greater than 0.005%. In order to obtain clean steel, the track is packaged and vacuum degassed. The worst field of view for oxides according to ASTM E45/84 is B1. The field of view for silicate type inclusions is C1.