Theory of Welding Processes - Practice Flashcards

Vocabulary flashcards covering core concepts, mathematical relationships, arc dynamics, heat sources, metallurgical reactions, phase transformations, and stresses from the Theory of Welding Processes lecture.

Theory of Welding Processes

A fundamental discipline that studies the physical essence of forming permanent joints based on interconnected thermal, metallurgical, and thermo-deformational processes.

Welding Arc

A powerful electrical discharge in a gas medium characterized by high temperature and high current density.

TIG Process

A gas tungsten arc welding process where the non-consumable tungsten electrode serves as the cathode and the metal being welded serves as the anode.

Cathode Zone

The region of the welding arc characterized by the highest electric field strength.

Anode Zone

The region of the welding arc into which the main share of heat enters.

Arc Column

The central plasma region of the welding arc located between the cathode and anode zones.

Arc Force Impact Relation

Expressed by the equation $F_0 = k \times I_0^2$, where $F_0$ is the force effect of the arc, $I_0$ is the current strength, and $k$ is a coefficient, showing that force is proportional to the square of the current.

Drag Force

A force acting on the molten weld pool during TIG welding that is caused by the plasma jet issuing from the cathode.

Archimedes Force

A buoyancy force acting in the weld pool caused by density differences within the molten liquid.

Electromagnetic Force

A force arising in the weld pool from the passage of electrical current through the molten metal.

Marangoni Force

A force caused by the surface tension gradient in the weld pool that, along with plasma jet drag force, dominates the formation of convective flow patterns.

Diffuse Cathode Spot Effect

A condition that reduces the force impact of the welding arc on the weld pool by a factor of $1.6$ to $3.2$ compared to a concentrated cathode spot in argon.

Fourier Law of Heat Conduction

The equation governing temperature distribution during welding, given by \frac{\frac{\text{d}T}{\text{d}t} = a \nabla^2 T} where $T$ is temperature, $t$ is time, and $a$ is the coefficient of thermal diffusivity.

Instantaneous Point Source

A heat source calculation model used to evaluate rapid pulse heating.

Continuous Moving Source

A heat source calculation model used for stationary welding regimes.

Fast-Moving Powerful Source

A heat source calculation model applied to high-speed welding processes.

Thermal Cycle of Welding

The variation of temperature over time for a specific point in the metal during the welding process.

Deoxidation

A key metallurgical interaction in the weld pool involving the chemical reduction of oxides to purify the molten metal.

Columnar Dendrites

Elongated crystals formed during weld pool solidification that grow from the fusion boundary toward the center of the weld in the direction opposite to arc movement.

Liquation

The uneven distribution of chemical elements and impurities throughout the volume of the weld seam.

Grain Diameter Formula

The equation $d = \frac{k \times R}{n}$, where $d$ is grain diameter, $R$ is crystal growth rate, $n$ is nucleation rate, and $k$ is a constant coefficient.

Primary Crystallization

The initial stage of structure formation occurring directly from the liquid melt as the weld pool cools.

Secondary Crystallization

Solid-state phase transformations occurring during the cooling of the weld seam and heat-affected zone (HAZ), forming microstructures such as ferrite, pearlite, bainite, or martensite.

Weldability

The capability of a metal to form a defect-free, high-quality welded joint without developing cracks.

Hot Cracks

Defects formed during high-temperature crystallization as a result of liquation and tensile stresses.

Cold Cracks

Defects arising after the joint cools down, often driven by martensite formation and hydrogen accumulation.

Temporary Welding Stresses

Transient thermal stresses that exist dynamically during the welding process due to non-uniform expansion and contraction.

Residual Welding Stresses

Permanent elastic-plastic stresses that remain in the welded structure after it has completely cooled.