Special features regarding the hardening of valves
The surface hardening of automotive valves presents a major challenge for many heat treatment processes. The reasons for this include the following:
- This involves the treatment of high-alloy steels.
- The tolerances for the diffusion layer thickness are very narrow.
- Demands for dimensional stability and form retention are high.
- Valves must not scratch.
- Large piece quantities are produced.
Plasma nitriding of valves
In comparison with hard chrome plating, and other nitriding processes, plasma nitriding is a very efficient and environmentally friendly way of treating valves. Plasma nitriding offers the following benefits, including:
- Perfect reproducibility
- Option of treating at low temperatures
- Substances harmful to the environment are not used
- Optimum automation capability
We would like to present you with one of our fully automated systems for treating valves. In this case, our customer was able to replace chrome plating by using the Eltropuls process. In doing so, the customer saves on costs and helps protect the environment.
- Piece quantity 120,000 valves per workday
- 4 different component types
- 2 different materials (X50CrMnNiNbN21.9 and X45CrSi9.3 steel)
In joint discussions, we and our customer opted for a fully automated solution. The valves are delivered to the Eltropuls line directly on the conveyor belt out of the machining process. The Eltropuls line takes on the following tasks:
- Cleaning the valves
- Loading the racks by swivel-arm robots
- Transporting the loaded racks to the plasma nitriding plant
- Automatic plant process start
- Transporting the racks with nitrided valves out of the plasma nitriding plant
- Unloading the valves onto a conveyor belt
To keep all customer requests at a low price, creative solutions were called for. Grippers are used which transport several valves at once. The automation system recognises the different types of valve, subsequently adjusting the grip and deposit points. Employee errors are ruled out as a result.
After approx. one-year project duration, we and our customer are thrilled!
The required cycle time was undercut by 0.72 s/part. Exceptional quality is produced. For the high-chrome-content steel X50CrMnNiNbN21.9, 13 ± 3 μm is achieved for the thickness of the diffusion zone in series production. For the X45CrSi9.3 ferrous steels, the range of thickness in the diffusion zone is 24 +/- 3 μm. The costs for treating the components were below 10 cents.