A. Welding power supply external characteristics of GMAW welding of the welding power source according to the type of external characteristic can be divided into three categories: level characteristics (constant voltage), the steep drop characteristics (constant current) moderate drop characteristics. When the protective gas is inert gas (pure Ar), Fu Ar and oxidizing gases (eg CO2), widely used in the production level features power when the wire diameter is less than φ1.6mm. This is because the level characteristics of power with the constant speed wire feeding system has many advantages, no-load voltage by changing the power to adjust the arc voltage, by changing the wire feed speed to adjust the welding current, so the Types Of Welding Electrodes adjustment more convenient. The use of this power of the external characteristic, when the arc length changes can have a stronger self-regulation; short-circuit current, the arc is relatively easy. Power its external features of the actual level features are not truly flat, but with a certain down-dip, down-dip rate is generally not more than 5V/100A, but still has the above advantages. When the wire diameter thick (greater than φ2mm), commonly used in production decline characteristics of power supply wire system with variable speed Diego. As the wire diameter coarse, arc self-regulation is weak, the slower recovery in the arc length changes alone arc self-regulation is difficult to guarantee the stability of the welding process. The need for additional as general submerged arc welding arc voltage feedback circuit, the arc voltage (arc length) changes timely feedback sent to the wire feed control circuit to adjust the wire feed speed, arc length timely recovery. Two. The main technical parameters of the power output adjusting the parameters of MIG welding power source: The rated input voltage (relative to the number, frequency, voltage), the welding current range, the rated duty cycle (%), no-load voltage, load voltage range, power external characteristic curve of type (flat characteristic, slow down the outside characteristics, the steep drop in the external characteristic) and so on. Usually according to the needs of the welding process to determine the requirements of the welding power source technology parameters, and then selected to meet the requirements of Nickel Electrodes. (1) The arc voltage of the arc voltage is the voltage drop between the wire ends and the workpiece, not a power voltmeter indicates the voltage (power supply output voltage). Pre-adjustment of the arc voltage is achieved by adjusting the power of the no-load voltage or the slope of the external characteristic. Level features power by adjusting the no-load voltage to arc voltage regulator. Slow down or drop characteristics of the power supply through the adjustment of the slope of the external characteristics of arc voltage regulator. (2) The current size of the welding current level features power by adjusting the wire feed speed to achieve, and sometimes appropriate to adjust the no-load voltage to the current small amount of adjustment. Slow down or drop characteristics of power by adjusting the slope of the external characteristic.

Welding technology as a traditional process after a century of development, its field of application involves all walks of life, nearly a hundred kinds of welding processes, mechanical manufacturing, aerospace, automotive, electronics and other industries have become the other connections can not be replaced technology. In particular, China is still in the process of industrialization, steel production and consumption, according to the first in the world, and welding technology still plays a very important role. Throughout the industrialized countries, the iron and steel power with Welding Wires

Hot-rolled thick plate products are mainly used in shipbuilding, building structures, bridges, boilers and pressure vessels, transport pipeline, offshore platform, construction machinery and other important occasions, increasing product quality Welding Material. This requirement is reflected in the following aspects:

(1) meet the strength, toughness index requirements;
(2) excellent service performance, including high resistance, low temperature performance, fatigue resistance, resistance to media corrosion;
(3) good welding performance, including a wide range of welding process adaptability, high crack resistance, applicable to large heat input welding;
(4) compliance with the regulations;

Which is one of the main requirements for weldability, steel production enterprises in their efforts to solve the key technologies. Micro-alloyed steel products to improve and enhance the weldability core.

Smelting and rolling technology advances

1 pure steel technology

Micro-alloying can not be separated from the overall progress of the metallurgical technology, hot metal pretreatment, steelmaking, ladle refining and vacuum refining refining technology, much lower than the previous low carbon steel content of impurity elements make steel in S, P, etc. and low-alloy steel.

To performance, for example, the pure steel smelting technology to achieve the following levels:

Solidification cracking incidence with a significant reduction of the impurity elements, along with greatly reduced, and no longer be the focus of attention and research.

Due to the structural design requirements of use, the performance of the steel sheet thickness direction can not be ignored. Elimination of the billet middle segregation technology is getting more sophisticated, and greatly reduce the degree of segregation, improved Z-thick plate performance.