Heat Input Formula

Heat Input Formula

In arc welding, the Heat Input Formula and arc energy are two important energy metrics. This energy is applied to the object to form a weld. Refers to characters such as weld length, bead, weld spot or section diameter. Heat input into the weld is a function of time. Heat input and arc energy are the two most important energy metrics in the arc welding process. This energy is applied to the part component to create a weld. The weld seam length, bead, spot weld diameter or cross-section are examples of properties. The amount of heat applied to the weld changes over time. The Heat Input Formula is an important parameter for the arc welding process. The Heat Input Formula maintains perfect weld quality. It can be defined as the amount of electrical energy supplied to the weld during the welding process. The amount of heat used for welding is calculated as a function of time. Faster cooling rates are often measured in welds due to embrittlement of the heat-affected zone. For example, adequate Heat Input Formula is required when working with materials that tend to form hydrogen-induced cracks. 

The amount of heat used in welding affects the cross-sectional area of ​​the weld. The associated slow cooling results in the formation of austenite grains in the HAZ, reducing toughness. High Heat Input Formula welding has a wide weld seam and is widely used for submerged arc welding. The deep and narrow geometries of high heat input arc welding can increase the likelihood of solidification cracking. Weld beads are smaller in low heat input welds such as B. Multilayer welding. Rapid cooling can create hard, brittle zones in the HAZ and risk hydrogen cracking, necessitating the use of preheating or thermal limiting. Extramarks is the best learning website which provides the best study material for every subject. Students can take the help of Extramarks for learning resources related to the Heat Input Formula and prepare for their examinations.

What Is Heat Input?

The majority of processors do not care about heat input. In many cases, that is fine. However, when welding microstructurally sensitive materials, it is important to know the heat input. This is why Heat Input Formula is important in some specific applications. This is because it greatly affects the cooling rate. A higher cooling rate is usually measured in welding because it causes embrittlement in the heat-affected zone. For example, when dealing with materials prone to hydrogen cracking where adequate heat input is critical. Heat input is an important parameter for the arc welding process. Heat supply controls perfect weld quality. The definition of heat input states that Heat Input Formula is the amount of electrical energy applied to the weld during the welding process. 

The Formula For Heat Input

The Heat Input Formula is:

Heat generation = voltage x current x elapsed time x 1000

Accurate measurement of arc voltage is difficult. However, most often one measures the load voltage at the output terminals of the power supply.

Heat input affects the cooling rate during the welding process. This affects the microstructure of the weld metal and affects the heat-affected zone (HAZ). Microstructural changes directly affect the mechanical properties of the weld metal and heat-affected zone (HAZ). Therefore, it is very important to control the heat input to achieve a strong microstructure and quality welds.

The heat input is therefore the arc energy according to the European system. Therefore, the following formula applies to European systems: Heat Input = Thermal Efficiency × Arc Energy

Solved Examples For Heat Input Formula

Q.1: Calculate the Heat Input Formula for a motor running at 2000 V with a current of 5500 calories. It has a range of 10 meters and a duration of 40 seconds.

Solution: Given data parameters are:


Current = 5500A

Distance traveled = 10 m

time = 40 seconds

Heat Input Formula = voltage × current × travel time × 1000

Assigns any value to the given expression.

Heat input = 2000 x 5500 x 4010 x 1000 

 The heat input is therefore 44000 Joules/meter.

  1. 2: A heat engine is running at a voltage of 1500V. The current flowing is 3400A. Find the heat input when the distance is 24 meters and the time is 80 seconds. 

Solution: the given parameters are


Current = 3400A

Distance = 24m

time = 80 seconds

Heat Input Formula = voltage × current × travel time × 1000

Substitute all values ​​into the resulting formula.


= 17000

 The heat input is therefore 17000 joules per meter.

For more examples of the questions involving the Heat Input Formula, students can visit the Extramarks website.

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