In the operation of gas - shielded welding machines, several parameters play a crucial role, and they work together to affect the welding quality and effect.

**Current**: It refers to the magnitude of the current passing between the welding wire and the workpiece during the welding process, which has a decisive influence on the penetration depth of the weld. As the current increases, the penetration depth deepens. However, it is necessary to be cautious of adverse conditions such as excessive weld width, excessive reinforcement, severe spatter, and even burn - through of the workpiece caused by excessive current. Conversely, if the current is too small, it is easy to result in insufficient penetration and welding defects such as lack of fusion.

**Wire Speed**: It represents the speed at which the welding wire is fed from the wire spool to the welding arc area. The wire speed must be accurately matched with the current and voltage. If it is too fast, it will cause the welding wire to accumulate in the molten pool, resulting in excessive weld reinforcement and frequent spatter. If it is too slow, it will lead to insufficient weld filling and failure to meet the penetration requirements.

**Inductance**: During short - circuit transfer welding, inductance is used to regulate the waveform of the welding current, thereby affecting the molten droplet transfer process. Reasonable adjustment of inductance can optimize the frequency and stability of the molten droplet transfer and reduce spatter generation. Increasing the inductance will slow down the rise rate of the short - circuit current and make the molten droplet transfer more gentle, but excessive inductance may disrupt the stability of the arc.

**Burnback**: When welding stops, the burnback function can cause the end of the welding wire to burn back a short distance, effectively avoiding the formation of a large molten ball at the end of the wire and creating favorable conditions for the next successful arc - starting. By effectively controlling the burnback time and current, the shape of the end of the welding wire can be optimized, the arc - starting success rate can be improved, and the spatter during arc - starting can be reduced.

**Pre-gas**: Before the welding is officially started, the pre - gas function will first deliver shielding gas to the welding area for a period of time, aiming to empty the air and prevent the weld from being oxidized. Sufficient pre - gas time can create a good protective atmosphere for welding and effectively guarantee the weld quality. If the pre - gas time is too short, the weld is very likely to be oxidized at the initial stage of arc - starting, which will have an adverse impact on the appearance and performance of the weld.

**Post-gas**: After the welding is completed, the post - gas will continue to deliver shielding gas to the welding area for a period of time. Its role is to protect the newly solidified weld metal from air oxidation. This function can effectively reduce the occurrence of defects such as pores and oxidation and improve the corrosion resistance of the weld.

**2T/4T (Two - step/Four - step Operation Modes)**: The 2T mode is simple to operate. Press the welding gun switch to start welding, and release the switch to stop welding. The 4T mode is relatively more complex. After pressing the switch to start welding, the welding will continue after releasing the switch. Press the switch again to stop wire feeding, and release the switch to completely stop welding. The 2T mode is suitable for simple and short - term welding operations and is convenient to operate. The 4T mode is more suitable for long - term continuous welding operations. Welders can control the welding process more flexibly and reduce hand fatigue.

**SPOT**: The SPOT function is specifically used for intermittent and short - term welding operations, and only one welding spot is formed each time. When fixing the position of components or making local connections, SPOT welding can quickly and efficiently achieve the welding task and can accurately control the size and spacing of welding spots.

**Wire Diameter Choose**: It is necessary to carefully select a suitable welding wire diameter according to factors such as welding process requirements and the thickness of the welded parts. Thicker welded parts usually require the use of thicker welding wire to ensure sufficient filling volume and penetration depth. Thin - plate welding should use thinner welding wire to prevent burn - through of the welded parts and ensure good weld formation.

**Gas Selection**: Appropriate shielding gas should be carefully selected for gas - shielded welding according to factors such as welding materials, welding processes, and welding quality requirements. Different shielding gases have different effects on the welding process and weld quality. For example, carbon dioxide gas has a low cost and is suitable for welding carbon steel, but the spatter is relatively more. The mixed gas of argon and carbon dioxide can reduce spatter and optimize weld formation, and is often used for welding stainless steel and other materials. Reasonable gas selection helps to improve weld quality and reduce the occurrence probability of welding defects. 

In conclusion, each parameter of the gas - shielded welding machine - Current, Voltage, Wire Speed, Inductance, Burnback, Pre-gas, Post-gas, 2T/4T mode, SPOT, Wire Diameter Choose, and Gas Selection - plays an indispensable role in the welding process. Accurately understanding and controlling these parameters is the key to achieving high - quality welding and meeting diverse welding requirements. Whether you are a novice welder eager to quickly get started or an experienced professional striving for further improvement in the craft, a deep understanding of these parameter knowledge will open the door to excellent welding skills for you, making you more proficient in the welding field, creating more perfect, strong, and high - quality welded works, and helping your career reach new heights.