Flow measurement in oil-hardening baths / quenching basins

Measuring flow in quenching basins



Process data

Measuring task:
Flow velocity measurement for process regulation and monitoring quality in the hardening bath

Measuring point:
At the heat conducting plates in the quenching basin

Measuring range:
Typically 0.2 … 2 m/s in two directions

Process pressure:
Hydrostatic pressure depending on insertion depth

Process environment
80 … 130 °C


Your advantage

For measurements in oil and water hardening baths vertically or horizontally. Sensors can be used as fixed or portable installations.     

Measuring data can be transferred directly to process control. If portable measurement is needed, measuring data can be saved in the handheld unit for evaluation at a computer.

Tried and tested
The automotive infustry and its suppliers  use our vane wheel sensors for this application


Quenching is an important step in heat treatment of metallic materials like motoric components, machines or gears to target certain hardness grades and hardening depths in the material. Usually quenching happens through immersion in a quenching basin.

Different quenching media are used depending on the task. It’s important that the entire element is evenly surrounded by flowing liquid. There are circulating pumps in the quenching basins that move the quenching medium and therefore provide an even heat distribution. Baffles in the heating bath support the process. Special sensors measure flow in the quenching basin. It’s an importan process parameter and therefore a quality factor.

Höntzsch has been delivering vane wheel flow sensors for many years to engine manufacturers in the automotive industry and many more. The sensors play an important role in wear resistance especially with drive technology.       

Recommended products

Vane wheel ZS25 … ZG1

ProductProduct data sheet

Handheld unit flowtherm NT.2

Product Product data sheet

Flow monitoring in quenching basins ensures properties of steel.

Even back in the ancient world and medieval times people have tried to make metals harder. It was a mystery for quite some time how red heat achieved such a high level of hardness through quenching.

In the 2nd half oft he 19th century the switch from alchemy to chemistry and metaphysics to physics prepare the foundation for modern hardening. Unlike wrought stell, mild steel could be alloyed which allowed hardening of thicker components and tools.

The invention of construction steel in the 19th century led to alloyed steel that could be refined with modern procedures in hardening shops.

Why is steel quenched in hardening shops?

Once heated to a certain temperature depending on material and degree of alloy steel changes its structural conditions. If the steel is cooled down quickly enough in this state in the quenching tank it can’t return to its original structure. A hard outer layer develops in the quenching basin.

The process in the quenching basin itself is of crucial importance. It is also important to adhere to the critical cooling rate to make sure the component cools down evenly. Otherwise tensions can arise and cause cracks in the component


How does quenching work in the hardening process

Quenching medium can be water, oil and aqueous polymer solutions depending on the steel grade.
Unalloyed carbon steel is hardened in water, lower alloyed steel in oil. In order to reach all areas of the component to be hardened or quenched, it has to be moved in the hardening bath. Circulation pumps in the quenching basin ensure continuous flow. In addition heat conducting plates in the basins support the even distribution of the liquid in the oil hardening bath or in the water hardening bath.


Why is flow in the quenching basin so important?

The achieved quenching speed in the quenching basin is of decisive importance for the hardening process. Medium flow in the hardening bath is a central factor in process control and thus for the steel quality.

Using vane wheel sensors specifically adjusted to this measurement can be used in the water hardening bad horizontally and vertically no matter what kind of hardening bath. The sensors can also be moved in the quenching basin for purely stationary measurements at relevant points in the quenching basin of the hardening shop. This allows recording the spatial distribution of flow in the hardening bath reliably.


What makes our sensors a perfect match for hardening baths?

The sensors measure reliably in different temperatures and aggresive media. Made from stainless steel they’re suited for the use in hardening baths, whether it’s oil or water, and can be used with a transducer oder handheld unit.

The handheld unit comes in especially handy when flow has to be measured at different places of the hardening baths. It records measuring values that are then available for later evaluation.

Höntzsch can calibrate sensors for any hardening shop in our own calibration laboratory to document the current measurement accuracy.