Heat Input

on . Posted in Welding Engineering

Heat input, abbreviated as $$H_i$$, refers to the amount of thermal energy that is introduced into a material or system and is commonly used in various contexts such as welding, material processing, and thermodynamics.

In the context of welding, heat input is a critical parameter that describes the amount of energy applied to melt and fuse the materials being welded.  It affects the overall quality and integrity of the welded joint.  The heat input is typically calculated by multiplying the welding current, voltage, and the arc time.  It's essential to control heat input during welding to avoid issues such as distortion, cracking, and changes in material properties.

In broader thermodynamic terms, heat input can refer to the amount of heat added to a system during a process.  For example, in a chemical reaction, heat input is the energy required to raise the temperature of the reactants to the necessary level for the reaction to occur.  Similarly, in heating or cooling processes, the heat input is the energy added to or removed from a substance to change its temperature.

Heat Input Formula

$$H_i = A \; V \; ( 0.06 \;/\; s ) \; T$$     (Heat Input)

$$A = H_i \;/\; V \; ( 0.06 \;/\; s ) \; T$$

$$V = H_i \;/\; A \; ( 0.06 \;/\; s ) \; T$$

$$s = 0.06 \;/\; ( H_i \;/\; A \; V \; T )$$

$$T = H_i \;/\; A \; V \; ( 0.06 \;/\; s )$$

Symbol English Metric
$$H_i$$ = heat input $$F$$ $$K$$
$$A$$ = welding current $$I$$ $$C\;/\;s$$
$$V$$ = arc voltage $$V$$ $$kg-m^2\;/\;s^3-A$$
$$s$$ = welding speed $$ft\;/\;sec$$ $$m\;/\;s$$
$$T$$ = thermal efficiency (depends on the welding process used) $$dimensionless$$

Heat Input Formula

$$H_i = 60 \; A \; V \;/\; 1000 \; s$$     (Heat Input)

$$A = H_i \; 1000 \; s \;/\; 60 \; V$$

$$V = H_i \; 1000 \; s \;/\; 60 \; A$$

$$s = 60 \; A \; V \;/\; 1000 \; H_i$$

Symbol English Metric
$$H_i$$ = heat input $$F$$ $$K$$
$$A$$ = welding current $$I$$ $$C\;/\;s$$
$$V$$ = arc voltage $$V$$ $$kg-m^2\;/\;s^3-A$$
$$s$$ = welding speed $$ft\;/\;sec$$ $$m\;/\;s$$

Tags: Thermal Welding