Metal Heat Treatment: the best cooling solutions

  1. FIELD OF APPLICATION

Production of printed, cast or mechanically machined metal parts, subsequently subjected to heat treatment to give them particular structure or hardness, strength, toughness or other qualities.

  1. DESCRIPTION OF THE PROCESS

Most parts intended for the mechanical sector (automotive, machine tools, conveyor belts, gears, screws and bolts, etc.) require a heat treatment after processing.

The main treatments of metals or metal alloys may include (by way of example):

  • annealing
  • normalization
  • hardening
  • tempering
  • distension
  • reclamation
  • solution annealing
  • cementation
  • nitriding

The heating furnaces can be cooled with disposable water or by tower; water is also used for rapid cooling of the pieces, according to the following possibilities:

  • direct contact with the piece to be cooled (direct tempering in water);
  • through water / oil exchanger, where the latter comes into contact with the piece (oil tempera).

 

  1. NEED FOR COOLING

In this application sector the evaporative tower or the adiabatic cool water coming from the heating furnaces of the pieces to be treated, as well as for tempering water cooling.

The heat load to be dissipated is determined based on the power of the furnaces. Considering that the discharge from the appliances is generally free, it is advisable to bring the hot water into a tank, from here to send them to the cooler and drop them in a cold water tank.

Generally, the temperature difference to be made for cooling the heating furnace and the heat-treated parts is generally 5 – 10 ° C, with temperatures entering the cooler between 30 ° C and 40 ° C and temperatures between 25 ° C and 30 ° C.

Is it better to install an evaporative tower or an adiabatic cooler?

First of all, it depends on the plant requirements. The cooling tower is most recommended if you want to acquire a solution with small dimensions capable of dissipating a greater quantity of heat in a unit of time. If instead the need is concentrated on saving cooling water, being able to count on greater surfaces, you can opt for an adiabatic cooler.

A further parameter to consider is the quality of the liquid to be cooled. Generally, the need is to cool relatively dirty process water (unless these have been filtered before ending up in the hot tub). An adiabatic cooler is only applicable with clean water that does not clog the batteries. For this it is better to rely on an open circuit evaporative tower, which can also be fitted with different exchange packs depending on the various water qualities.

Powers to be disposed in these plants are often quite limited: generally, the range is 15 to 2,000 KW. As a consequence, small-medium sized cooling towers are dimensioned, pre-assembled and easily transportable on site.

 

  1. REPLACEMENT PARTS FOR THE COOLERS

The components of a cooler need to be changed periodically to always have optimal performance. These include:

  • mechanical equipment such as the motor-fan unit;
  • heat exchange packs (for cooling towers), with a more or less fine network depending on the quality of inlet water;
  • distribution system (for cooling towers) better if in PVC.

Not only can a cooling consultant provide the best components for coolers also of different suppliers: he can also advise on the frequency with which to change the different parts.

 

  1. HYDRAULIC SYSTEM Typical scheme of a hydraulic system for cooling a metal heat treatment plant

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