WeldsIt refers to the connection part formed by the base metal melted during welding and the welding material after cooling. The shape and size of the weld (width, residual height, thickness, etc.) directly affect the mechanical properties and service life of the welded joint. Therefore, understanding and controlling the parameters that affect the depth and width of the weld seam is an important part of the welding process design and quality control.
The parameters that affect the depth and width of the weld are mainly in the following categories:
Welding process parametersIt refers to the parameters selected to ensure the welding quality, such as welding current, arc voltage, welding speed, line energy, etc. These parameters determine the strength, distribution, and movement of the weld heat source, which affects the melting range and solidification process of the weld.
Generally speaking, the welding current is the main factor that determines the thickness of the weld, and the arc voltage is the main factor that affects the width of the weld. The welding speed and line energy comprehensively reflect the heat input per unit length of the weld, which affects the penetration depth and width of the weld. Specifically, when other conditions are constant:
When the welding current increases, the penetration depth and residual height of the weld increase, and the solution width remains unchanged (or slightly increased).
After the arc voltage increases, the penetration depth of the weld decreases slightly, the solution width increases, and the residual height decreases.
When the welding speed increases, the penetration depth, solution width and residual height of the weld decrease.
Therefore, in order to obtain a good weld shape, that is, to obtain a weld forming coefficient that meets the requirements, these parameters are mutually restrictive and must be comprehensively considered and selected.
Welding methodIt refers to the arc type, polarity, protection method, etc. used in welding. The connection method refers to the connection between the electrode (welding wire) and the workpiece during welding, such as DC forward connection, DC reverse connection, AC, etc. Different welding methods and jointing methods will affect the stability of the arc, thermal efficiency, droplet transition form, etc., thereby affecting the melting and solidification of the weld.
Generally speaking, in the case of melting electrode arc welding, the penetration depth and penetration width of DC reverse connection are larger than that of DC positive connection, which is due to the large amount of energy released by the workpiece (cathode). In the case of tungsten argon arc welding, the penetration depth of DC forward connection is the largest, and the reverse connection is the smallest. Welding aluminum, magnesium and alloys have the problem of removing the oxide film on the surface of the molten pool, and it is better to use AC, and reverse connection can also be used when welding thin plates. Welding other materials is generally connected by direct current.
Welding postureIt refers to the tilt angle of the electrode (welding wire) relative to the welding direction during welding, such as forward tilt, backward tilt, etc. The welding angle refers to the inclination angle of the weldment relative to the horizontal plane during welding, such as uphill welding, downhill welding, etc. Different welding postures and angles will affect the effects of arc force, gravity, surface tension, etc. on the liquid metal in the weld pool, thereby affecting the flow and forming of the weld.
Generally speaking, when the electrode (welding wire) is tilted forward, the penetration depth of the weld decreases, the solution width increases, and the residual height decreases. The opposite is true when the electrode (wire) is tilted back. After the weldment is tilted, the welding method can be divided into two types: welding from high to low is called downhill welding; Welding from a low place to a high place is called uphill welding. During uphill welding, the penetration depth and residual height of the weld increase, and the solution width decreases. When downhill welding, the penetration depth and residual height of the weld decrease slightly, and the solution width increases slightly. Therefore, in order to obtain a suitable weld shape, it is necessary to select the appropriate welding posture and angle according to the welding method and weldment thickness.
Bevel shapeIt refers to the cutting method of the weldment before welding, such as unilateral groove, bilateral groove, V-shaped groove, U-shaped groove, etc. Clearance refers to the butt spacing of the weldment before welding. The bevel shape and gap affect the amount of fill and heat input to the weld, which in turn affects the melting and solidification of the weld.
Generally speaking, when the groove depth and width are increased, the penetration depth and solution width of the weld increase slightly, and the residual height decreases significantly. When the gap is increased, the penetration depth and width of the weld increase, and the residual height decreases. Therefore, in order to obtain a suitable weld shape, it is necessary to select the appropriate groove shape and clearance according to the welding method and weldment thickness.
The chemical composition of the base metal and welding material will affect the melting temperature, melting rate, droplet transition, slag viscosity, melt pool fluidity, etc., which will affect the melting and solidification of the weld.
Generally speaking, the lower the melting temperature of the base metal and the welding material, the faster the melting rate, the easier the droplet transition, the smaller the slag viscosity, the better the fluidity of the weld pool, the greater the penetration depth and width of the weld, and the smaller the residual height. Therefore, in order to obtain a suitable weld shape, it is necessary to select the appropriate welding process parameters and methods according to the chemical composition of the base metal and welding materials.
In order to ensure that the depth and width of the weld meet the design requirements and improve the mechanical properties and service life of the welded joint, it is necessary to reasonably select and control the welding process parameters and methods. Commonly used welding quality control methods are as follows:
Welding process specification:According to the chemical composition of the base metal and welding materials, welding methods and connections, groove shape and clearance, welding position and angle and other factors, the appropriate welding process parameters are formulated, such as welding current, arc voltage, welding speed, line energy, etc., as well as the corresponding welding operation specifications, such as electrode (welding wire) inclination, welding wire elongation, flux accumulation height, shielding gas flow, etc., as the guidance and basis of the welding process.
Welding process test:Before formal welding, the selected welding process parameters and methods are tested and verified, the shape and size of the weld, as well as the mechanical properties and defects of the welded joints are observed and detected, the rationality and feasibility of the welding process are evaluated, and if necessary, adjusted and optimized.
Welding process monitoring:In the welding process, real-time monitoring and control of welding process parameters and methods, such as the use of sensors, instruments, computers and other equipment, the welding current, arc voltage, welding speed, line energy and other parameters are measured, displayed, recorded and adjusted to ensure the stability and consistency of the welding process.
Welding quality inspection:After welding, the shape and size of the weld, as well as the mechanical properties and defects of the welded joint are detected and evaluated, such as visual inspection, size measurement, non-destructive testing, mechanical test and other methods are used to inspect the depth, width, residual height, forming coefficient and other indicators of the weld, evaluate the strength, toughness, corrosion resistance and other properties of the welded joint, and identify and analyze the defects such as unwelded penetration, burn-through, undercut, and welding nodules of the weld to judge whether the welding quality meets the standards and requirements.
The depth and width of the weld are important factors affecting the performance and life of the welded joint, and they are affected by a variety of parameters, such as welding process parameters, welding method and jointing method, welding posture and angle, groove shape and clearance, base metal and chemical composition of welding materials, etc. In order to ensure that the depth and width of the weld meet the design requirements, it is necessary to reasonably select and control the welding process parameters and methods, and adopt welding process regulations, welding process tests, welding process monitoring, welding quality inspection and other methods to improve the welding quality and efficiency.