6 Tips for Resistance welding-Auto Body Technology

Resistance welding Yolo Materials Industry 16th, Aug 2023 15:00pm

As labor costs continue to rise, a new and better welding method is now used for the automotive body welding procedure. This innovation has replaced manual welding practices in auto production, thus gaining favor among a growing number of automotive parts manufacturers.

In this blog, we will explain the basic principles of resistance spot welding.

1. The principle of resistance welding

Welding with Joule heat.
Q=0.24I2Rt=0.24IEt(cal)…①
Formula ① As shown in the figure below, the workpiece is pressurized between the upper and lower electrodes, energized, and resistance welded.
When the resistance of the welding part is R (Ω), the welding current is I (A), and the energization time is t (sec), the welding part will generate heat according to formula ①. Therefore, the temperature of the welded portion rises, and melting occurs.

5 elements of resistance spot welding

The above factors are related to the calorific value Q and the calorific position. That is to say, the factors affecting the welding effect during spot welding are: current I, energization time t, contact resistance R, current density (electrode tip) and electrode material. The contact resistance R decreases as the applied pressure increases.

Contact Resistance

The resistance caused by the thin oxide layer formed on the surface of the workpiece (skin resistance) and the resistance caused by the cross section of the current flow (concentrated resistance).

In the figure above, R2, R4…the resistance of the material itself; R3…the resistance between the upper and lower workpieces; R1, R5…the resistance between the electrode and the workpiece. Contact resistance refers to R1, R3, R5.

The role of resistence welding electrodes

So what is current density?

Current density refers to the current value in a unit cross section. If the current density is kept stable, welding defects can be prevented.

Due to the conduction of a large current (electrode action 1), the tip of the electrode will generate heat. And because the top of the electrode will be widened due to the pressure, the current density will become smaller. Therefore, as the number of welding increases, the nugget becomes smaller (poor welding). Therefore, in welding quality management, electrode management (replacing or grinding electrodes after a certain number of welding) becomes very important.

The principle of resistance spot welding

1. The resistance spot welding method is a metal joining method that uses the resistance of the workpiece itself, the pressure applied to the workpiece, and the large current that is conducted to generate Joule heat at the contact part of the workpiece and melt it.

2. Five elements that determine welding quality:

① Current value
② Power on time
③ Add pressure
④ Current density
⑤ Electrode material

How to choose the resistance welding electrode material?

①High intrinsic resistance workpieces-> Choose small intrinsic resistance materials as electrodes
②Small intrinsic resistance workpieces-> Choose high intrinsic resistance materials as electrodes
example:

Selection of welding current, time and pressure

Current specification

A specification – high current for a short time (best specification)
B specification one medium time medium current (medium specification)
C specification a long time small current (ordinary specification)

How to choose the right current?

Initially set a low welding current, if the welding current is gradually increased, spatter will occur. Then, a current value slightly lower than the current value when spatter occurs is an appropriate current.

The current value varies depending on the followability of the welding machine’s pressurization system. The better the followability of the welding machine, the easier it is to apply smaller pressure and larger conduction current, that is, to obtain the best welding effect.

Selection of welding time

The heat generated at the soldered part increases with the energization time. However, the amount of heat dissipation from electrodes and welded parts also increases with the energization time.

Therefore, the temperature of the welded part tends to be saturated after a certain period of time. After the temperature is saturated, the weld nugget will not increase even if the power-on time is prolonged. In addition, surface indentation and thermal deformation will also increase, causing adverse metallurgical effects on the material.

In addition, welding for a long time is also disadvantageous from the viewpoint of working hours and power consumption.

The most suitable specification in the above figure is the area with a pressurization force of 5kg and a current of 500A. To increase the welding strength, it is necessary not only to increase the current, but also to increase the pressure. At this time, slowly increase the current and pressure from low to select the best range.

Resistance welding is also often used in motors, such as the welding of terminals and enameled wires, and the main points of this type of welding will be introduced step by step.

Now, imagine a resistance welding solution that combines precision and efficiency for perfect connections. Meet our cutting-edge tungsten, molybdenum insert coper resistance welding electrodes – they’re incredibly reliable, durable, high-performing, and designed for a longer work life!

NDB technology

NDB (non-defective bonding) does not require any solder due to. The integration of copper, tungsten, and molybdenum ensures a strong connection with a strength exceeding 130Mpa, without any internal holes.

oxidation resistance

(2) The welding electrode materials is better to have higher oxidation resistance, less tendency to form alloys with weldment materials

conductivity

Our electrodes have excellent electrical and thermal conductivity, for continuous cooling of the electrode tip. This significantly increases the service life and reduces consumption. Additionally, the tip has been densified, resulting in a high-density and uniform internal structure.

Customized Mahining

With our extensive experience in the production and processing of resistance welding electrodes, we can also provide improved design solutions tailored to your specific needs.

Get Price Now

Tungsten Electrode Needle

with Factory Direct Price

Resistance Welding NDB Tungsten Electrode

>>More Details

Yolo Materials Industry

Blog