What factors in process manufacturing can cause corrosion of electric heating tubes?

What factors in process manufacturing can cause corrosion of electric heating tubes?

① The wear and tear of mold materials will produce worn materials. Wear materials have poor corrosion resistance and strong adhesion. Under the action of liquid media, electrochemical reactions first occur between them and the stainless steel matrix, followed by or accompanied by interface corrosion, until comprehensive or diffusion corrosion (including pitting corrosion) occurs.

② During process transfer, collisions can cause wounds to the passivation film on the surface of the pipe, sometimes even blunt impacts, and the wounds can be as deep as the parent material. In natural environments, this type of wound can also produce pitting corrosion with increasing time or humidity.

③ Externally heated corrosion. On the one hand, high welding temperature can cause phase transformation in the heating zone, which not only changes the mechanical properties of the welding material, but also causes trace elements to overflow. The overflow process also leaves channels in the parent material, leading to pore corrosion. At the same time, high temperature causes rapid oxidation of the surface material, which can result in poor mechanical properties and even failure of the welded position after welding. On the other hand, although the hot corrosion ability of brazing flux can remove the oxide layer of the material, it has a counterproductive effect on surfaces that do not require treatment, damaging the corrosion resistance.

④ During the polishing process, material surface damage is caused by scratches, damage to surface purity, and chemical corrosion of polishing agents.

6.6 Rated power measurement:

6.6.1 The rated power should be measured using a power meter, voltmeter, or ammeter after the component is under sufficient heating or simulated conditions and reaches the working temperature for 10 minutes. The accuracy of measuring instruments should not be lower than level 1.5.

6.6.2 The working temperature of components shall be determined using the following methods:

Under sufficient heating conditions, temperature measurements are taken using a surface thermometer or thermocouple at the designated temperature measurement points on the component casing. The average temperature measured at each measurement point is the working temperature. Take three temperature measurement points, located at the highest, lowest, and middle temperature points on the heating surface of the component.

6.6.3 When multiple components are connected in series to the power supply, the power of each component should be measured separately.

6.6.4 During factory inspection, it is allowed to measure the cold DC resistance value of the component and convert the power according to equation (4):

In the formula: P - Power, unit: kW

U - Rated voltage, in volts

R0-- Cold state DC resistance, unit: Ω

Ct -- Working temperature coefficient of electric heating wire

The cold DC resistance and its deviation, as well as the temperature coefficient of the heating wire, must be clearly specified in the technical documents. The accuracy of the instrument used to measure the cold DC resistance should not be lower than level 1

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