1. Brass Weldability
Brass is a copper-zinc alloy, and due to zinc's low boiling point (only 907℃), it is very easy to evaporate during the welding process, which is the biggest problem in brass welding.
Under high temperature conditions during brass rod arc welding, the amount of zinc evaporation can reach 40%, which leads to a decrease in the mechanical and corrosion resistance properties of the welded joint and increases its sensitivity to corrosion under tension. .
The evaporated zinc is immediately oxidized into zinc oxide in the air, forming white smoke, which causes great difficulties in the operation and harms the welder's health.
Therefore, when welding brass, it is necessary to strengthen ventilation and other protective measures.
Poor solderability of brass can cause problems such as porosity, cracking, zinc evaporation and oxidation during welding.
To solve these problems, silicon-containing welding wire is commonly used in welding, because silicon will form a dense oxide film on the surface of the molten pool, blocking the evaporation and oxidation of zinc and preventing hydrogen invasion.
After welding, annealing at 470-560 ℃ can be carried out to eliminate stress and prevent the phenomenon of “self-cracking”.
2. Brass welding methods
The commonly used welding methods for brass in production are electric arc welding and argon arc welding, and their main process points are as follows:
(1) Electric arc welding: Brass welding rod with bronze core wire such as ECuSn-B (T227), ECuAl-C (T237) is used. Pure copper core wire such as ECu (T107) can be used for brass castings that do not require high welding requirements.
The power supply must have DC positive connection and the angle of the V-shaped groove must not be less than 60°-70°.
When the plate thickness exceeds 14 mm, the welding surface must be carefully cleaned before welding to remove all oil impurities that will generate hydrogen gas.
Short arc welding must be used during operation, and the welding rod must not be swung horizontally or longitudinally, but only move along the straight line of the weld. The welding speed should be fast, not less than 0.2-0.3m/min.
In multilayer welding, the oxide film and slag between the layers must be removed. The copper liquid in brass has high fluidity, so the molten pool must be in a horizontal position. If the molten pool needs to be tilted, the tilt angle should not be more than 15°.
(2) Argon arc welding: HSCuZ-1 brass-tin welding wire (HS221), HSCuZn-2 iron-brass welding wire (HS222) and HSCuZn-4 brass-silicon welding wire (HS224) are used in manual tungsten and argon arc welding.
These welding wires contain high zinc content and produce large smoke during welding. Bronze welding wires such as HSCuSi (HS211) and HSCuSn (HS212) can also be used.
Welding parameters for manual welding of brass with tungsten and argon arc are shown in the table.
| Materials science | Plate thickness/mm | Groove shape | Tungsten electrode diameter/mm | Power supply type and polarity | Welding current/ | Argon gas flow rate A/(L/min) | Preheating temperature/℃ |
| Common brass | 1.2 | Termination | 3.2 | DC direct connection | 185 | 7 | Not preheating |
| Tin brass | two | V-shaped | 3.2 | DC direct connection | 180 | 7 | Not preheating |
Due to the evaporation of zinc, which destroys the protective effect of argon gas, a larger nozzle opening and argon gas flow rate must be selected when welding brass.
Generally, preheating is not required before welding, except for joints with a thickness greater than 10mm and joints with a significant difference in thickness between the welding edges, in which case only the thickest part of the welding edge needs to be preheated. heated.
The power supply can use DC or AC positive connection. When using an AC power source for welding, the amount of zinc evaporation is relatively small.
Higher welding current and faster welding speed should be used for welding parameters.
The welding parameters for welding brass plates with a thickness of 16-20 mm are: welding current 260-300A, tungsten electrode diameter 5 mm, welding wire diameter 3.5-4.0 mm , nozzle opening of 14-16 mm and argon gas flow rate of 20- 25L/min.
To reduce zinc evaporation, the filler wire can be “short-circuited” with the workpiece during operation, and the arc can be started and maintained on the filler wire as much as possible, avoiding direct arc contact with the base metal. The base metal is heated and melted primarily by heat transfer from the molten metal.
When welding, single-layer welding should be carried out as much as possible. For joints with a thickness of less than 5 mm, it is better to weld them in one go.
After welding, the welding should be heated to 300-400°C for annealing to eliminate welding stress and prevent the brass component from cracking during use.
3. Brass Tig Welding
1. Brass solderability
Brass is a copper-zinc alloy. Because zinc has a lower boiling point of just 907°C, it is prone to evaporation during the soldering process, posing a significant challenge when soldering brass.
Under high welding temperatures, up to 40% of zinc can evaporate during electric arc welding.
This substantial evaporation of zinc leads to a decrease in the mechanical and corrosion resistance properties of the welded joint, also increasing its susceptibility to stress corrosion cracking.
The evaporated zinc is immediately oxidized to zinc oxide in the air, forming white smoke that makes operation difficult and harms the welder's health.
Therefore, it is essential to reinforce ventilation and other protective measures in places where brass is welded. The poor weldability of brass can lead to problems such as porosity, cracking, and zinc evaporation and oxidation during welding.
To solve these problems, silicon-containing welding wire is often used because silicon forms a dense silica layer on the surface of the molten pool, inhibiting the evaporation and oxidation of zinc and preventing hydrogen intrusion.
After welding, an annealing treatment at 470-560°C can be used to relieve stress and prevent “self-cracking”.
2. Brass welding methods
In production, common methods for welding brass include electric arc welding and argon arc welding. The essential points of these processes are the following:
(1) Electric arc welding
The electrode used is a bronze core electrode, such as ECuSn-B (T227), ECuAl-C (T237). For brass castings that do not require high-quality welding, an electrode with a pure copper core such as ECu (T107) can be used.
The power supply uses direct current with the electrode connected to the positive terminal, and the angle of the V-shaped groove should not be less than 60°-70°.
For plates thicker than 14 mm, the surface of the welded parts must be carefully cleaned before welding to remove all oil impurities that can produce hydrogen gas.
During operation, short arc welding must be used and the electrode must not be moved from side to side or back and forth, but only in a straight line along the weld.
The welding speed should be fast, not less than 0.2-0.3m/min. In multilayer welding, the oxide film and slag between the layers must be thoroughly cleaned.
Brass has high fluidity, therefore, ideally, the melting pool should be in a horizontal position. If the pool is to be inclined, the angle must not exceed 15°.
(2) Argon arc welding
During manual argon arc welding with tungsten electrode, the welding wires used are tin-brass HSCuZ-1 (HS221), iron-brass HSCuZn-2 (HS222), silicon-brass HSCuZn-4 (HS224) .
These wires contain a large amount of zinc, resulting in a large amount of smoke during welding. Brass welding wire HSCuSi (HS211), HSCuSn (HS212) can also be used.
The welding parameters for manual tungsten electrode and brass argon arc welding are listed in the table.
| Material | Common brass | Tin brass |
| Thickness/mm | 1.2 | two |
| Groove type | Butt joint | V-groove |
| Tungsten electrode diameter/mm | 3.2 | 3.2 |
| Power supply type and polarity | DCEN | DCEN |
| Welding current/A | 185 | 180 |
| Argon gas flow rate/(L/min) | 7 | 7 |
| Preheating temperature/℃ | No preheating | No preheating |
Because the evaporation of zinc disrupts the protective effect of argon gas, a larger nozzle diameter and argon gas flow must be used when welding brass.
Preheating is generally not necessary except when welding joints with thicknesses greater than 10 mm and joints with significantly different edge thicknesses. In the latter case, only the thickest edge of the part needs to be preheated.
Direct current with the electrode connected to the positive terminal or alternating current can be used as a power source. When welding with alternating current, the amount of zinc evaporation is less.
Welding parameters should employ a higher welding current and faster welding speed.
Welding parameters for 16-20mm thick brass plates are: welding current 260-300A, tungsten electrode diameter 5mm, wire diameter 3.5-4.0mm, nozzle diameter 14-16 mm, argon gas flow 20-25L/min.
To reduce zinc evaporation, the filler wire may “short-circuit” to the part during operation, starting and maintaining the arc in the filler wire to prevent the arc from directly affecting the base material, which is heated. and melted mainly by heat transferred from the metal in the weld pool. When welding, single-layer welding should be carried out as much as possible, and joints with a thickness of less than 5 mm should ideally be welded in one go.
After welding, the workpiece must be heated to 300-400°C for annealing to eliminate welding stress and prevent the brass component from cracking during use.
