As a specialist in low-tension annealing, Smit Heat Treatment is responding to increasing demand from the market: the vertical annealing of drive shafts. Applying heat treatment to a vertically hanging object prevents it from distorting under the influence of its own weight.


Vertical annealing up to a maximum length of 4.5 metres

Smit Heat Treatment atmospheric bogie hearth furnaces will anneal hanging drive shafts up to a maximum length of 4.5 metres. Low-tension annealing removes internal stresses from the steel. This makes the material more homogeneous in terms of its structure and prevents dimensional deviations and distortions.

Vertical annealing prevents distortion in drive shafts

Straightness guaranteed

Industrial pumps and gas generators are driven by long steel shafts. When such shafts undergo heat treatment, it is imperative that they do not become warped by high temperatures. If these objects are annealed horizontally – resting on minimal support points – then there is a high risk that the shaft will start to sag and exit the furnace slightly crooked. And that’s an undesirable situation, because even a slight warp will cause serious vibrations at high rotation speeds. Placing the shaft in a vertical hanging position prior to annealing prevents such warping from occurring and guarantees the straightness of the shaft.

Very even temperature spread

Vertical annealing involves suspending the object from the roof of the furnace. Because heat rises, the challenge is to create an even spread of heat throughout the furnace. During vertical annealing, it is essential that the temperature at the top of the furnace is roughly equal to the temperature at the bottom. Smit Heat Treatment meets this requirement with its very spacious atmospheric furnace that features a large air volume. This means the shaft is treated at a constant temperature along its entire length.

Smit Heat Treatment furnaces are TÜV-certified for a very even temperature spread as per Merkblatt HP 7/1.

Localised vertical annealing

In addition to heat treatment of the entire shaft in a bogie hearth furnace, it is also possible to carry out localised heat treatment on a hanging drive shaft using resistive or inductive heating. This might involve low-tension annealing of a welding seam or a local repair.

Further information

Do you require further information about the vertical annealing possibilities at Smit Industrial Heat Treatment? Then feel free to contact us without obligation. We’d be delighted to help you!

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