FIELD OF INVENTION:
This invention relates to the method of manufacturing of seamless steel tubes. More particularly the invention relates to an improved apparatus of guiding the mandrel thrust block with plug in the piercing process.
BACKGROUND OF THE INVENTION:
During manufacturing of seamless steel tubes there are several stages starting from billet entry into the rotary hearth furnace to cutting the tubes to the required length. The hollow billet is formed in the piercing mill over a plug located between two rolls located in skew angle. The plug is attached at one end of a long mandrel and the other end of the mandrel is fixed on the mandrel thrust block. The mandrel thrust blocks moves back and forth for every piercing operation. The mandrel thrust block is mounted on four wheels and is guided on the sides by two wear strips on either sides. These wear strips gets worn out easily due to high friction arising out of sliding contact. Due to this, plug is not guided properly and failure occurs in front axle wheel assembly. Hence, there is a need to find a suitable method of guiding.
PRIOR ART:
Some of the manufacturers use sliding type of wear strips for guiding of mandrel thrust block. This causes of faster wearing of wear strips and also results in unequal wearing of the wear strips. Hence, this method is not recommended.
OBJECTS OF THE INVENTION:
It is therefore an object of present invention to propose a method of guiding the mandrel thrust block with plug.
A still further object of present invention is to propose a roller type guide wheel for guiding the mandrel thrust block during the back and forth motion.
SUMMARY OF THE INVENTION:
Accordingly, there is provided six guide rollers, three on either side of the mandrel thrust block. The rollers are centered on individual shafts and mounted on bearing. The shaft is assembled on a housing. The three rollers are mounted such

that they press against the guide rails and rotate on its axis while moving back and forth.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. Some embodiments of system or methods in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
Figure-1 shows the general cross piercing process in a schematic diagram in accordance to the prior art.
Figure 2 shows the side wear strip arrangement before the modification in accordance to the prior art.
Figure 3 shows the arrangement after the modification with roller type guide wheels in accordance to the present invention.
DETAILED DE DESCRIPTION OF THE PREFERRED EMBODIMENTS :-
Figure 1 shows the general cross piercing process in a schematic diagram. The mandrel thrust block (1) moves back and forth for every piercing process from basic position to piercing position. The mandrel thrust block has four locating wear strips (2), two on either side. There are two long wear strip (3) one on each side to guide the mandrel thrust block and maintain its position during the back and forth motion. The mandrel thrust block is mounted on four wheels (4) moving on surface of the outside of the piercing mill (5). The mandrel thrust block supports the piercing mandrel (6) with piercing plug (7) at end. Piercing takes places between the rolls (9) when the hot billet (8) enters from inlet side of the piercing mill. Once the piercing is over the mandrel thrust block moves to basic position with the pierced hollow bloom. This is a repeated process.

Figure 2 shows the side wear strip arrangement before the modification. The mandrel thrust block gets guided on the guide (10). There is a sliding contact that existing between the wear strip (2) and guide (10) due to which the wear rate is high.
Figure 3 Shows the arrangement after the modification with roller type guide (11) wheels with six rollers. Three rollers placed on each sides. The rollers have two deep groove ball bearing mounted on a shaft for enabling smooth rotation.

WE CLAIM:
1. An improved apparatus of a mandrel thrust block (1) that includes plurality of locating wear strips (2), plurality of long wear strip (3), piercing mandrel (6), piercing plug (7); wherein the mandrel thrust block is moved in forward and backward direction on a piercing mill (5) to pierce a billet; characterized in that
the mandrel thrust block (1) is aided by plurality of roller guide wheels (11) to reduce the frictional force.
2. The improved apparatus of a mandrel thrust block (1) as claimed in claim 1, wherein the roller guide wheels comprises of groove ball bearing mounted on a shaft to enable smooth rotation.
3. The improved apparatus of a mandrel thrust block (1) as claimed in claim 1, wherein the billet is received by rolls (9) of the piercing mill.
4. The improved apparatus of a mandrel thrust block (1) as substantially described and illustrated herein with reference to the accompanying drawings.
5. The improved apparatus of a mandrel thrust block (1) as claimed in claim 1, wherein the roller guide wheels may be six in number.