thermite rail welding kits

Some Matters Need to Pay Attention in Rail Thermite Welding Construction Process

Thermite welding of railroad tracks is essentially a casting process. No external power source is required because the molten metal for casting is produced via a thermite reaction. Thermite rail welding kits are manufactured to include all the necessary materials required for welding. Even in remote areas, the welding of a thermite rail can be completed by a team of two welding technicians in as little as 45 minutes.

Orbital thermite welding operating principle

When the thermite flux is put into the refractory crucible and a high-temperature match is ignited with an igniter, the thermite reaction begins. After the reaction is completed, the liquid steel is automatically released from the bottom of the crucible into the refractory mold to weld the two ends of the rail. The mold features rail geometry and controls the casting and curing process. After the molten steel has cooled down, further heat treatment can be used to better improve the mechanical properties of the rail welding head.

Preparatory work

1. Selection of flux: must be matched with rail type; Must use the valid flux; Do not use damp flux;

2. Equipment and process: need to use the right frame or the right beam to the right rail; Use French flux. Require French preheating.

3. Preparation work at the welding site: check whether there are hidden dangers causing safety accidents on the site, such as wet work site, flammable or explosive materials in the close distance; Connect the preheating gun, pipe, barometer, oxygen, propane gas cylinder and other devices in advance, and note that the gas cylinder should be kept at a certain safe distance from the welding site.

Construction technology

1. Rail end face treatment

The end face of the welded rail head should be cut vertically by a rail sawing machine, and oxygen cutting is not allowed to prevent oxidation layer and oil pollution on the end face of the rail. In order to avoid small cracks in the screw hole after heating and damage at the screw hole, the distance between the screw hole and both ends of the rail should be greater than 100mm; Use hand grinder or wire brush to remove the rust, the rail end cleaning length should reach 100 ~ 150mm, if the rail rust is serious, it should be removed within 1m of the rail end, otherwise it will affect the alignment.

2. The rail ends are aligned

The alignment of rail end is the most difficult and critical part in thermite welding process. The alignment mainly includes adjusting the size of the rail seam (25±2mm), cusp adjustment, horizontal alignment, unequal tilt adjustment of four steps, generally should be adjusted 2 to 3 times, the order is always the rail seam – cusp – horizontal – unequal tilt. Attention should be paid to the alignment process: the general direction of the rail must be ensured before the alignment; If there are low joints, they should be treated in advance; With the right frame to the rail, to ensure the adjustment of the cusp, level and tilt, to prevent the wrong alignment and rail distortion, so that the welding head stress increase or lead to stress concentration; Do not touch the rail and tie in the welding area, alignment frame, etc. After the correct alignment, the bottom of the rail should be plugged with a wooden wedge to maintain good condition.

3. Install the sand mold

Ensure that the mold components are not damaged or damp; The two side sand molds are run in the weld, the gap and height difference between the side sand mold and the rail are eliminated, and the skin is prevented. If there is a clip, especially at the corner of the clip, will produce stress concentration, thus affecting the strength of the welding head; After the base and sand mold are installed, cover the mold mouth with cardboard or other clean objects to prevent debris from entering and affecting the welding quality; Too little mold mud will dry and crack, resulting in molten steel leakage; Mold mud too much, will not be able to dry, moisture can not be discharged, easy to form pores. Therefore, the mold mud should be applied evenly from the bottom to the top.

4. Preheat

Preheating is the soul of thermit welding and the most critical part of the process. Gas pressure and flow should be sufficient; Preheating gun installation must be symmetrical in the center to ensure uniform preheating on both sides of the rail; If the temperature is low and the pressure is insufficient, the preheating time can be extended appropriately for 30s to 1min; Ensure good preheating effect, especially good preheating effect of rail bottom; Pay attention to the preheating of the rail head during the preheating process, the color of the rail head turns red to end the preheating, and the standard preheater time should be used as a reference, not as a standard; Anti-tempering plug is a wearing part, should be equipped with several sets of spare, so as not to affect the preheating quality.

5. Pour

Ignition should be carried out as soon as possible after the preheating, and the preheating to pouring time should be less than 30s; High temperature matches inserted into the solder center depth of about 25mm, too deep or too shallow will affect the reaction speed; Two people hold the plugging rod, once the molten steel leakage phenomenon occurs, plug it in time, if it cannot be blocked, once it leaks out, it should immediately leave the scene.

6. Push the tumor

Not too early, or it will lead to heat strain, creating a heat crack; The cutter head is 1.5 ~ 2mm away from the top surface of the rail to prevent the head from being planted when pushing the tumor.

7. Polish

Use a copying grinder to polish the whole section of the welding head, do not use hand grinding wheel; When grinding the top surface of the rail, there is a margin, do not over-grind (loss); Remove all clamps at the waist, bottom and corners of the rail to avoid stress concentration.

8. Construction precautions when the temperature is below 15 ° C

Before preheating, both sides of the rail end should be heated to 37 ° C within 1m on each side; After pushing the tumor, hold it for 10 minutes with a heat shield and then polish it to prevent the martensitic tissue that is brittle and brittle in the metallographic tissue due to excessive cooling.

9. Other

A groove should be carved at the bottom of the large steel column with a holding chisel or Angle grinder after the mold removal; The surface of the small steel column should be polished with hand grinding wheel, do not use a hammer to strongly knock, so that the bottom of the rail crack source, and then develop into a fracture.

Thermite rail welds are considered safe, reliable and cost-effective components for rail freight and passenger tracks, including heavy freight and high speed passenger transport. It is important to prioritize research to improve railway management and inspection techniques to mitigate the occurrence of failures.

GloryRail’s goal is to become the world’s leading manufacturer and supplier of rail system consumables, tools, and related welding services, and to reach long-term cooperation parties and partners with related companies, focusing on the commitment to quality, integrity, and compliance. Our aluminothermic welding equipment meets the requirements of ISO9001:2008 QMS.

The main products of GloryRail include iron III DE series, 50DE, 60DE, QU series, QU70, QU80, QU100, QU120, A65, A75, A100, A120, A150, and various types of rail thermite.