Tubes - ISMT Limited
Tubes
At ISMT we have invested in sophisticated facilities and developed specialized processes for the manufacture of bearing tubes. Apart from producing tubes from standard bearing grade steels such as SAE 52100 and DIN 100 Cr6, the company also produces tubes from tailor made steels.
The steel used for the manufacture of bearing tubes is produced exclusively through the electric arc furnace route, is ladle refined and is vacuum degassed. As a result, the steel is extremely clean ensuring a high fatigue life for the bearing. ISMT supplies bearing tubes to the major bearing manufacturers throughout the world.
Oxygen Content
Oxygen content < 15ppm. On specific request oxygen content < 10 ppm can be offered.
Inclusion Rating
The tubes are tested to ensure that the steel is free from injurious imperfections such as piping, cracks, porosity, segregation or injurious inclusions as referred to in ASTM-381. The inclusion rating is evaluated in accordance with Plate III of ASTM E-45 ensuring that the length of any inclusion does not exceed 0.65 mm and that the worst field of each inclusion type from each specimen does not exceed the limits given below.
Inclusion Rating Worst Field
| A | B | C | D | Type |
| 2.0 | 1.5 | - | 0.5 | Thick |
| 1.5 | 0.5 | - | 0.5 | Thin |
Heat Treatment / Microstructure
The tubes are spheroidized and annealed to ensure that the microstructure consists of spheroidized commentate in a ferrite matrix with carbide size conforming to Plates 2 to 4 as per IS 4398-1972 and CG 2.1 - 2.3 as per SEP 1520-78. We ensure that there is no carbide network and the structure is free from segregation of carbides in either streak or cluster form.
Hardness
| Condition | Brinell Hardness |
| Hot finished, spheroidized | 230 BHN max. |
| Hot finish, spheroidzed & peeled | 230 BHN max. |
| Hot finished, spheroidized & stress relieved | 207 BHN max. |
| Spheroidized, cold pilgered / roto-rolled | 250-320 BHN |
Decarburisation Depth
Hot finished: 0.50 mm max. per side Cold finished: 0.20 mm max. per side
Dimensional Tolerances**
| Description | Size Range | Tolerance | |
| OD (mm) | OD (mm) | Wall t (%) | |
| Hot rolled | 38 - 75 > 75 - 100 > 100 - 125 > 125 - 200 |
+/- 0.4 +/- 0.5 +/- 0.6 +/- 1.0% |
+/- 5% +/- 5% +/- 5% +/- 10% |
| Hot rolled and Peeled | > 36 - 120 | +/- 0.40 - 0.00 |
+/- 5% +/- 5% +/- 5% +/- 10% |
| Cold pilgered / Roto rolled | 19 - 80 > 80 - 91 |
+ 0.30 - 0.00 + 0.40 - 0.00 |
+/- 5% +/- 5% |
**Note: Tighter tolerances can be offered on specific request.
| Eccentricity | Straightness | |||
| Hot finished & peeled | 10% of wall thickness | Cold pilgered / roto-rolled | 1 : 1000 | |
| All other tubes | OD < 125mm: 5% of wall thickness OD > 125mm: 10% of wall thickness |
Hot finished / hot finished & peeled | 1 : 600 | |
Lengths
Tubes are generally supplied in random lengths of 3 - 4.5 mts with 10% up to 2mts.
End Preparation
Square cut & one end chamfered.
Size Range
