### Box-type resistance furnace parameter setting method

Box-type resistance furnace parameter setting method

1. Determination of furnace temperature

When rapid heating is used in the box furnace, the service life of the resistance wire is considered. Generally, the furnace temperature is set at 920~940℃ (resistance wire is made of chromium-nickel material), 940~960℃ (resistance wire is made of iron-chromium-aluminum material) or 960 ～980℃ (The resistance wire is a material containing alloy components such as niobium and molybdenum).

2. Determining the amount of furnace installed

The amount of furnace installed is generally determined according to the furnace power and use area. The principle is: the surface of the furnace wall of the first batch of workpieces has reached the specified temperature before the furnace is installed, and the furnace temperature can quickly return to the specified temperature after each installation. If the furnace load is too large and does not match the furnace power, the furnace temperature will not be restored for a long time, which will affect the correctness of the time calculation. In mass production, it can be “reduced into parts” and carried out continuously in batches.

3. Determination of heating time

The rapid heating time is generally calculated according to the effective size of the workpiece cross section, and determined according to the actual situation and past experience:

(1) The rapid heating time of a single piece can be calculated as follows:

Where t: rapid heating time (s);

a: Fast heating time coefficient (s/mm);

d: The effective diameter or thickness of the workpiece (mm).

In the box-type resistance furnace, the effective diameter or thickness of the workpiece is less than 100mm, and the rapid heating time coefficient a is 25-30s/mm;

The effective diameter or thickness of the workpiece is greater than 100mm, and the rapid heating time coefficient a is 20-25s/mm.

Calculate the rapid heating time according to the above formula, which should be adjusted appropriately according to the determined furnace temperature and determined after passing the process verification.

(2) When parts are produced in batches, in addition to the calculation of the above formula, the rapid heating time should be added according to the installed furnace volume (m), the furnace density and the placement method:

When m＜1.5kg, no time is added;