a - unplated metals; b - clad metals ; in - details of unequal thickness; g - unlike metals;
s and s 1 - the thickness of the part; d is the calculated diameter of the cast core of the point or the width of the cast zone of the seam; h and h 1 - the amount of penetration; g and g 1 - the depth of the dent
Spot welding is a welding process in which parts are connected at one or several points at the same time.
Content
General information
In spot welding, the strength of the joint is determined by the size and structure of the weld point. This, in turn, depends on the shape and size of the contact surface of the electrodes, the strength of the welding current , the time it flows through the workpieces, the compression force and the surface condition of the parts to be welded. The performance of spot welding can reach 600 joints in 1 minute [1] . It is used to connect the thinnest parts (from 0.02 microns ) of electronic devices, for welding steel structures from sheets up to 20 mm thick in automobiles , aircraft and shipbuilding , in agricultural engineering and other industries [1] .
A special case of this type of welding is spot capacitor welding .
Technology
Spot welding is a type of contact welding , therefore, the technology is based on the thermal effect of electric current according to the Joule-Lenz law and the compression force of the parts to be welded. During welding, current flows from one electrode to another through the metal blanks. Contact spot welding electrodes are made of alloys with high electrical conductivity , so that the resistance in the electrode-workpiece contact is minimal. Therefore, in the places of contact of the part-part, the greatest heating occurs due to the highest value of electrical resistance . Heating and melting of the metal under the influence of electric current leads to the formation of a cast core of the weld point, the diameter of which is usually 4-12 mm [2] .
There are soft and hard spot welding modes.
- The soft mode is characterized by a longer welding time and smooth heating of the workpieces with moderate current forces, with a current density on the electrode working surface usually not exceeding 100 A / mm² [3] . The current flow time is usually 0.5-3 seconds [4] . The advantages of soft modes are lower power consumption compared to hard modes; lower network loads; less powerful and cheaper welding machines needed for spot welding; reduction of hardening of the weld zone. Soft modes are used for welding steels that are tempered.
- The hard spot welding mode is characterized by a short welding time, longer than in the soft mode, current values and a significant compressive pressure of the electrodes. Current densities reach 120-300 A / mm² when welding steel [3] . The current flow time is usually 0.1-1.5 seconds [4] . The pressure of the electrodes is usually taken in the range of 3-8 kg / mm² [3] . The disadvantages of hard modes include increased power consumed during welding; significant network loads; powerful welding machines. The benefits are reduced welding time and increased productivity. Rigid modes are used in welding aluminum and copper alloys with high thermal conductivity , parts of unequal thickness and unlike parts, as well as high alloy steels in order to maintain corrosion resistance [4] .
The current supply time during welding and the time of application of the compression forces, the current strength and the magnitude of the compression forces are determined by a given process sequence [5] .
Notes
- ↑ 1 2 Contact electric welding // Great Soviet Encyclopedia : [in 30 vol.] / Ch. ed. A.M. Prokhorov . - 3rd ed. - M .: Soviet Encyclopedia, 1969-1978.
- ↑ Spot welding process . Date of treatment July 26, 2009. Archived March 3, 2012.
- ↑ 1 2 3 Spot welding process . Date of treatment July 26, 2009. Archived March 3, 2012.
- ↑ 1 2 3 Spot welding . Date of treatment July 26, 2009. Archived March 3, 2012.
- ↑ Spot resistance welding // Autowelding.ru website
Links
- Spot welding in the home workshop
- Spot welding - material from the site www.svarkainfo.ru
- Spot welding - material from websvarka.ru
- Spot welding - material from top-samodelki.ru