GB/T5169.10 Fire hazard testing for electrical and electronic products Part: Basic test methods for hot wire/hot wire Hot wire devices and general test methods

4.1 Hot wire

The hot wire is made of nickel/chromium (>77% Ni/20 ± 1% Cr) wire with an outer diameter of 4.00 mm ± 0.07mm (before bending). scorching

The size of the wire loop is shown in Figure 1.

A new hot wire should be annealed for at least 10 hours at a current of at least 120 amperes before being applied to the experiment. The total annealing time can be

It is cumulative. To avoid damaging the thermocouple, it should not be installed during annealing. At the end of annealing, the depth of the thermocouple micropores needs to be determined

Confirm.

Note 1: In the first few hours of circulating current, the temperature of the new hot wire that has not undergone annealing treatment gradually decreases, and after a period of time, the temperature reaches

To balance.

The design of the experimental device should keep the hot wire on a horizontal plane, and during use, the hot wire should apply 0.95N to the specimen

A force of 0.10N. When the hot wire or specimen moves relative to each other in the horizontal direction, this pressure value should be maintained. The top of the heating wire enters and penetrates the sample

The depth should be limited to 7.0 mm ± 0.5 mm.

The design of the testing device should enable combustion or burning particles falling from the specimen to drip unobstructed onto the substrate described in 4.4

On the layer.

Two typical examples of experimental devices are shown in Figure 3a) and Figure 3b).

Note 2: The device shown in Figure 3b) is useful for testing heavy or irregularly shaped specimens.

The top of the hot wire is smoothly brought into contact with the specimen and maintained for 30 seconds ± 1 second. The appropriate approach and evacuation speed is about 10mm/s~

25mm/s。 However, in order to avoid an impact force exceeding 1.05 N during contact, the rate of approach should be reduced to near 0. During material melting

When detaching from the hot wire, the hot wire should not remain in contact with the sample. After the application time is up, slowly separate the hot wire from the sample to avoid the sample

Further heating and avoiding any air flow that may affect the test results. The depth at which the top of the hot wire enters and penetrates the specimen should be limited to

Within 7mm ± 0.5mm.