What Is Welding Velocity and its Impact on Quality?

What Is Welding Velocity

Welding velocity refers to the speed at which the torch or welding equipment travels during the welding process.

It is determined by factors such as material flow rate and thickness.

The appropriate welding velocity varies depending on the specific application.

For example, tube mill welding speed should be between 3 inches to 60 feet per minute, while lathe welding speed should range from 5 to 60 inches per minute.

Orbital welding equipment typically operates at a speed of 4 to 10 inches per minute.

The choice of welding velocity depends on the thickness of the parts being welded, with slower speeds used for thicker parts and faster speeds for thin walls.

Welding current, which determines the heat applied, is also interrelated with welding velocity, along with material, thickness, and shield gas.

Porosity, the formation of cavities in the weld pool, can be caused by factors such as poor gas shielding, leaks in the gas line, high gas flow rate, draughts, and excessive turbulence in the weld pool.

Precautions such as sealing air leaks, avoiding weld pool turbulence, using fillers with deoxidants, reducing gas flow, and preventing moisture absorption help prevent porosity.

Welding Velocity: Impact On Torch And Material Flow

Welding velocity, also known as weld speed, refers to the speed at which the torch travels during the welding process. It determines the quality and efficiency of the weld. The torch’s travel speed is influenced by factors such as material flow rate and thickness.

When welding, material flow rate and thickness directly affect the welding velocity. Thicker materials require a slower welding speed to ensure proper penetration and fusion. Conversely, thinner materials can be welded at a faster speed without compromising the integrity of the weld.

The torch’s travel speed should be carefully controlled to achieve the desired welding outcome. If the speed is too slow, excess heat input can result in distortion and overheating of the material. On the other hand, if the speed is too fast, insufficient heat may lead to inadequate fusion and weaker welds. Therefore, achieving the optimum welding velocity is crucial for producing high-quality and structurally sound welds.

Recommended Welding Speeds For Different Equipment

Different welding equipment requires different welding speeds to achieve optimal results. Here are the recommended welding speeds for various types of equipment:

• Tube Mill Welding: For tube mill welding, the welding speed should be between 3 inches to 60 feet per minute. The specific speed depends on factors such as material thickness and flow rate.

• Lathe Welding: When using a lathe for welding, the recommended welding speed ranges from 5 to 60 inches per minute. The chosen speed on the lathe should be based on the material thickness and other parameters.

• Orbital Welding Equipment: Orbital welding equipment operates best at a weld speed of 4 to 10 inches per minute. This range ensures precision and consistency in the weld.

• Starting Weld Speed for Rotating Parts: When welding rotating parts, it is advisable to start with a welding speed between 10 to 20 inches per minute. This allows for proper heat distribution and fusion during the initial stages of the welding process.

By adhering to these recommended welding speeds, welders can ensure that the welds are carried out efficiently and accurately for each specific piece of equipment.

Understanding The Relationship Between Welding Current And Heat Application

Welding current is a crucial factor in determining the amount of heat applied during the welding process. It is affected by various factors, including the type of material, thickness, welding speed, and the shield gas used.

Typically, welders start with a guideline of 1 amp per 0.001 inch of material thickness as a general starting point. However, it is important to make adjustments based on the specific conditions and requirements of the welding application.

The number of welding currents needed depends on the application and welding speed. In cases where higher welding speeds are required, it may be necessary to increase the welding currents to ensure adequate heat input and proper fusion throughout the weld.

To achieve the desired heat input, it is crucial to carefully adjust the welding current. Insufficient heat can result in incomplete fusion and inadequate penetration, while excessive heat can cause distortion, burn-through, and weakened welds. Therefore, it is essential to maintain a balance between the welding current, welding speed, and other parameters to obtain optimal welding results.

Causes And Forms Of Porosity In Welds

Porosity in welds refers to the presence of cavities caused by the release of gas from the weld pool as it solidifies. It significantly impacts the integrity and strength of the weld.

There are different forms of porosity, including:

• Distributed surface breaking pores: These are tiny bubbles spread throughout the weld.
• Wormhole crater pipes: These are tubular voids usually found at the end of the weld crater.

Porosity in welds is primarily caused by the absorption of gases such as nitrogen, oxygen, and hydrogen in the molten weld pool.

• Nitrogen and oxygen absorption usually results from poor gas shielding, which allows air to enter the weld zone. Even as little as 1% air entrainment in the shielding gas can result in distributed porosity.

Other causes of porosity include:

• Leaks in the gas line
• High gas flow rate
• Draughts
• Excessive turbulence in the weld pool

Hydrogen is a significant contributor to porosity and can come from:

• Moisture
• Grease
• Oil
• Surface coatings
• Surface treatments

Preventive Measures To Avoid Porosity During Welding

To prevent porosity in welds, several preventive measures can be implemented:

• Seal air leaks: Ensuring airtight gas delivery systems prevents the ingress of air, reducing the risk of porosity caused by oxygen and nitrogen absorption.

• Avoid weld pool turbulence: Excessive turbulence in the weld pool can trap gas and lead to porosity. Welders should minimize disturbances, such as excessive arc flicking and erratic welding motion, that can cause turbulence.

• Use filler with deoxidants: The use of filler materials containing deoxidants, such as silicon or aluminum, can help mitigate porosity by scavenging oxygen before it can cause issues.

• Reduce gas flow: Decreasing the gas flow rate can minimize the opportunity for air to enter the weld area.

• Eliminate draughts: Creating a controlled environment free from drafts can reduce the potential for air contamination during the welding process.

• Proper surface preparation: Ensure that electrodes, flux, and the workpiece surface are dry, clean, and free from grease, oil, and other contaminants that can contribute to hydrogen absorption and porosity.

• Avoid thick surface coatings: When working with weldable primers, ensure that they are not applied too thickly to prevent surface coating-related porosity.

By following these preventive measures, welders can minimize the occurrence of porosity and ensure the production of sound and reliable welds.

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Frequently Asked Questions

What is welding speed in welding?

Welding speed refers to the rate at which the welding torch moves along the surface being welded. It plays a crucial role in achieving optimal weld quality and consistency. Factors such as material thickness and complexity of the joint determine the appropriate welding speed. Generally, for parts that rotate under the torch, a speed between 10 and 20 inches per minute on the tungsten surface is recommended. When working with thick components, slower speeds are preferred, while faster speeds are suitable for thinner walls. The selection of the welding speed ensures efficient heat input and proper fusion, vital for a well-executed weld.

What is high velocity impact welding?

pulse welding (MPW), electrohydraulic forming (EHF), and magnetic pulse welding (MPW). In high-velocity impact welding, the two materials to be joined are accelerated towards each other at very high speeds, typically using an explosive charge or a magnetic field. The impact between the materials results in a rapid deformation and a high amount of energy being transferred, causing the materials to fuse together at the interface. This process can efficiently join dissimilar materials without the formation of undesirable intermetallic compounds, making it particularly useful in industries such as aerospace and automotive manufacturing, where the combination of different materials is often required for optimal performance and weight reduction.

What is weld porosity?

Weld porosity refers to the presence of cavities within the weld metal, caused by the entrapment of gas during the solidification of the weld pool. These cavities can manifest in various forms, including distributed and surface-breaking pores. Porosity negatively impacts the integrity and strength of the weld, compromising its structural stability. Therefore, it is crucial to prevent the occurrence of weld porosity through proper welding techniques and gas shielding to ensure a high-quality and defect-free weld joint.

What is arc voltage in welding?

Arc voltage in welding refers to the total voltage drop that occurs across the anode, cathode, and plasma regions. It is a crucial factor that significantly impacts the welding process. The arc voltage determines the heat input, penetration depth, and overall quality of the weld. By understanding and controlling the arc voltage, welders can achieve desired outcomes, such as proper fusion, minimal spatter, and a strong bond between the materials being joined.