The New Zealand Railways Magazine, Volume 2, Issue 12 (April 1, 1928.)
Treatment of Springs
Treatment of Springs.
Stripping.—When an engine is received for overhaul all the springs are cleaned in the lye vat and then forwarded to the spring shop for overhaul and repair. Instead of waiting for the return of these springs other springs are obtained from the ample supplies kept in stock. This is a feature of the new scheme—that sufficient stocks of all classes of springs are always kept on hand.
On receipt of springs from the lye vat they are placed in the stripping machine (illustration No. 1) and the buckles are removed. The leaves are then closely examined, broken leaves being replaced by new ones from a stock rack.
Cropping, Nibbing and Trimming.—Spring steel, which is procured in bars 18ft. in length, is cut to the required size (cold) in one end of the nibbing and trimming machine (illustration No. 2). The leaves are then placed in the page 39 furnace and the heated leaves are trimmed, if necessary, and then nibbed or punched in the centre. The leaves are then ready for forming and heat treatment.
Forming.—The leaf is first placed in the spring furnace (illustration No. 3) and brought to a temperature of 1650 degrees F. It is then placed in the forming machine (illustration No. 4) where a master leaf is already in position. The movement of a lever operates the hydraulic ram which pushes the leaf against an elliptical chain belt, and, when the ram is withdrawn, the leaf is left with the desired camber in it. This operation is speedily performed, there being very little loss of temperature during the process.
Quenching.—The leaf is next placed into a water-cooled oil quenching bath (illustration No. 4), containing Houghton's No. 2 soluble oil, and is then ready for the final operation.
Drawing.—After quenching, the leaf is passed straight through the spring furnace and the film of oil is burnt off.
At the same time it is pre-heated in readiness for treatment in the salt bath (illustration No. 5). A number of leaves are then placed in a perforated tray and lowered into the bath, which contains a specially prepared non-carburizing salt. The spring furnace (oil fired) is kept at a constant temperature of 650 degrees F.—thus any period of immersion ensures that every leaf received identically uniform treatment.
Assembling.—The leaves are next assembled in a banding press (illustration No. 6), the buckles having been previously heated in a small furnace placed alongside the press. The heated buckle is then placed over the assembled leaves and the springs placed under a double ram. which squeezes the buckle vertically and horizontally against the assembled leaves. The buckle is finally cooled off and the completed spring is painted ready for delivery to the finished spring rack.
Testing.—Under the new treatment the testing of springs and spring leaves is only a periodical necessity, its chief purpose being to keep a check on the different batches of steels.
Control of Temperature.—The temperature of all three furnaces concerned in the treatment of springs is regulated by the use of a special Cambridge Pyrometer (illustration No. 7). The reading is obtained by turning a knob indicating each individual furnace. It is now possible to control the vitally important factor in heat-treating of steel, viz., temperature. This was impossible under the old process.
The new plant is compactly arranged, all operations are carried out in their proper sequence, and all unnecessary handling has been eliminated.