Materials and welding requirements for tricone bit
1. High quality low-carbon alloy steel structure should be adopted for drill cone and tooth claw. Forgings shall be used if the diameter of the bit is not greater than 444.5mm, and castings shall be used if the diameter is greater than 444.5mm. The mechanical properties of the material shall comply with the provisions of Table 6.
Table 6 Mechanical properties of tooth and claw materials
Part name
Tensile strength Rm
MPa
Yield strength Rm
MPa
Section elongation A
%
Area reduction rate Z
%
Impact energy Aku
J
Insert tooth roller ≥1078 ≥833 ≥10 ≥40 ≥64
Tooth claws and steel tooth roller ≥980 ≥785 ≥9 ≥40 ≥47
Casting roller ≥760 ≥620 ≥8 ≥35 ≥45
Casting teeth ≥680 ≥550 ≥8 ≥30 ≥42
2. The tensile strength of the drill joint shall not be less than 490MPa.
3. The surface of the weld shall not have cracks, unfused, pores, arc pits, unfilled, slag and spatter.
4. The drilling bit connection thread shall be processed in accordance with GB/T 22512.2.
5. There should be no leakage of welding seam and runner system of drill bit after pressure test.
6. The bearing chamber of the sealed drill bit and the oil storage compensation system should be vacuumized before oil injection, and the vacuum degree should not exceed 5kPa.
7. The radial runout tolerance of the three cone back cones of a tricone bit against the connecting thread centerline shall not exceed that specified in Table 7.
8. The height difference between the three rollers of a tricone bit shall not exceed that specified in Table 8.
9. There should be no bounce and interference in the rotation of each roller.
Table 7 Runout tolerance of radial circle of cone back cone with connection thread
The bit diameter
in
3 1/2 to 5 3/4
5 7/8 ~ 8 1/4
8 3/8 to 11 5/8
11 3/4 to 19 7/8
20 or more
The bit diameter
mm
88.9 to 146.1 149.2 to 209.6 212.7 to 295.3 298.4 to 504.8 ≥508.0
Radial runout tolerance
mm
1.0 1.3 1.7 2.2 2.8
Table 8 Roller height difference
The bit diameter
in
3 1/2 to 5 3/4
5 7/8 ~ 8 1/4
8 3/8 to 11 5/8
11 3/4 to 19 7/8
20 or more
The bit diameter
mm
88.9 to 146.1 149.2 to 209.6 212.7 to 295.3 298.4 to 504.8 ≥508.0
Insert bit cone height difference
mm
0.8 0.9 1.1 1.3 1.6
Steel tooth bit cone height difference
mm
1.1 1.2 1.4 1.7 2.0