Monday, September 27

understanding Soldering : vacuum or gas soldering

Like many sheet metal terms, soldering and welding are used interchangeably. However, while these two operations are similar, their process and sub-techniques are different. The main difference between welding and soldering is melting. In soldering, metal fabricators heat the metal to be bonded but never melt them. In welding, metal fabricators melt the base metal.

Common features of vacuum and gas soldering are as follows: All solders are made of metal materials with a lower melting point than the base metal. Liquid solder is used to wet the base metal, fill the gap between the joints, and diffuse with the base metal to join the solders.

Differences between vacuum and gas soldering:

The principle of vacuum and gas soldering is basically the same, but there are large differences in the details and specific requirements. In terms of quality, vacuum brazing is much higher than gas brazing, mainly in terms of strength and cleanliness, but in terms of production efficiency, vacuum brazing is lower than gas brazing, and its cost is lower. Compared to gas soldering, the difference is as follows:

  1. The difference in the structure of the soldering furnace;
  2. Material differences;
  3. The requirement for the difference in details;
  4. The difference in soldering technology;
  5. Differences in product quality;
  6. Differences in production efficiency and cost.

1. The difference in the structure of the soldering furnace

Vacuum soldering: a closed furnace body is used. When soldering the gas in the furnace, it is necessary to pump out so that it reaches an approximate vacuum state (3.5 * 10 Pa), and then solder at elevated temperature. The purpose of vacuum brazing is to prevent the reaction between the work piece and oxygen and other active gases in the air during the brazing process and the exhaust gases in the furnace under high vacuum. Residual welding strength will be high with very low welding strength.
Gas brazing: continuous brazing method adopted. During the brazing process, nitrogen-filled gas is mainly used for brazing. The main purpose of nitrogen filling is to protect against oxidation of the weld, but since the furnace body is open, the protective layer of nitrogen cannot achieve uniformity, so the welding strength will be low.

2. Material differences

Vacuum Brazed Aluminum Material: The vacuum solder material uses a double composite material 4104, of which 4104 solder contains 1.5% magnesium. Its main goal is to punch AL2O3 on the surface of the work piece during high-temperature brazing, so that silicon in the material can flow with each other and achieve a welding effect. Typically, the surface of an aluminum alloy is protected by a thin layer of AL2O3. The melting point of AL2O3 is about 1200 degrees, so magnesium is needed to break it down.

Gas brazing: Vacuum brazing uses the 4343 double composite material. The 4343 solder does not contain magnesium, mainly due to the flux to break AL2O3 on the surface of the aluminum alloy.

3. The difference in accuracy requirements for parts

Requirement for accuracy of vacuum brazing of parts: the requirement for precision of parts is relatively high, which is less than 0.05 mm, otherwise the brazing will be virtual welding, which will ultimately lead to product leakage;
Gas soldering: the accuracy of the parts is not high, the gap is less than 0.2 mm, and the flow can be filled.

4. The difference in soldering technology

Vacuum Brazing Process:

First, the gas in the furnace is pumped out (mainly oxygen and other active gases in the furnace are removed to prevent Al from reacting again during the brazing process with the formation of AL2O3, which affects the quality of welding), and then welding is performed with heating. out. A flux is not required during welding because the magnesium element in the vacuum brazing material can destroy AL2O3 on the surface of the material and vacuum brazing is performed. There is a process of heat storage, this process can basically maintain a constant temperature of all products in the furnace, thereby increasing the strength of products during soldering. A vacuum brazing furnace requires about 4 hours because each product must have a vacuum brazing and cooling process before it leaves the furnace.

Gas soldering: vacuum is not required, the workpiece is directly protected by gaseous nitrogen. Before soldering, the workpiece must be coated with a flux. During brazing, AL3O 2 on the surface of the material is destroyed. CAB is a continuous track soldering at a speed of 350 mm / min (equivalent to 1.5 hours in a vacuum brazing furnace). There is no process for maintaining heat and vacuum pumping. And the cooling process.

5. Differences in product quality

Vacuum soldering:

The strength of products during soldering is relatively high, usually reaching more than 60 kg (a small gap between the parts, high vacuum, high magnesium content in the furnace seam); purity is relatively high (flux is not required, purity can reach less than 5 mg); the appearance of the products is relatively bright and metallic (a lower content of exhaust gases in the furnace, the absence of a gas oxidation reaction, even solder).
Gas protective soldering:

The soldering strength of products can only meet the requirements of ordinary customers. The total strength is about 30 kg. Purity is difficult to guarantee due to the need for flux. The appearance of the products is rather dull.

6. Differences in production efficiency and cost

Vacuum soldering:

The production cost of the product is relatively high: since each furnace needs vacuum pumping and heating, production efficiency is low; the product cannot be processed after failure, it can only be scrapped, so the cost of quality is also high;

Gas protective soldering:

The production cost of the product is relatively low: because it can be produced continuously without a vacuum and heating process, and production efficiency is high; The product can also be processed after failure, so the cost of quality is low.

The cost of products mainly includes the cost of soldering and the level of skill of the product.

  1. The cost of soldering each product is different;
  2. the speed of the vacuum brazing is 95%, the speed of the welding gas in the containment is 99%, the manufacturing cost is 4%, and the price of the product is 3%.

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