Air Carbon Arc Gouging is. a very useful metal removal process

In Agriculture Systems II We will use the Air Carbon Arc Process to meet: STANDARD 10 Students will fabricate with metal. AND…..

Objective 2: Use the air carbon arc gouging processes. 1: Perform safety inspections of equipment and accessories. 2: Set up for manual air carbon arc gouging operations on carbon steel. 3: Perform straight gouging operations on carbon steel.

Common methods of gouging are: Gouging is a way to remove metal! Mechanical techniques such as grinding, hand milling, routing, and chipping. Oxy-fuel gouging, which can be used only on carbon steels. Air carbon-arc gouging.

More information Click on the picture for more information

The air carbon arc process maybe used to: Cut metal, Gouge out defective metal Remove old or inferior welds Root gouging of full penetration welds Prepare grooves for welding.

More uses Removal of metal surface and internal defects. Removal of excess weld metal. Preparation of bevel joint edges for welding.

In maintenance and repair, operators might need to remove any of the following: Welds or metal to replace a worn or defective part. Worn hard-faced deposits so that hard-facing can be reapplied; Defects in a weld so the part can be re-welded.

Weld the groove after it has been back gouged. Back gouging a root pass on thick metal will make it possible to have 100% weld fusion in the joint. Weld the groove after it has been back gouged.

How would you fix the problem? What is this? “POROSITY” How would you fix the problem? To fix porosity in a weld, you could gouge it out to clean metal then re-weld.

Ways to remove Porosity. First clip Gouging out porosity in a weld so it can be correctly Re- welded Second clip

How about fixing a bad root pass? In a very short time! Click on start.

Air Carbon Arc -Gouging Air carbon arc gouging does not rely on oxidation like Oxy-fuel cutting does. It can be applied to a wide range of metals.

It differs significantly from both oxy-fuel cutting and plasma arc cutting. The process uses a carbon electrode, a standard Constant Current Welding power source (like SMAW welding).

How Air Carbon Arc Gouging works. An electric arc is established between the tip of a carbon electrode and the workpiece, it melts a pool of metal. Compressed air blows the melted metal away.

For effective metal removal The air stream is directed at the arc from behind the electrode and sweeps under the tip of the electrode

Connections

Parts of the Torch Insulated lever The Air Valve Electrode The Handle Compressed Air in The Head Amperage input

Parts of the Torch What they do: Electrode: Conducts the arc to the base metal. The Head: (holes) Directs the compressed air. Insulated lever: Used to open the jaws. The Air Valve: Air to the discharge holes. The Handle: Hold and control the torch. Compressed air in: From your compressor. Amperage input: From your power source.

What it will do: This process will work on anything that can conduct electricity and be melted with an arc. Steel, cast iron, stainless steel, copper, brass, aluminum. Magnesium alloy all can be destroyed with air-carbon-arc (because it will burn).

Carbon Electrodes Non-consumable (does not become part of the base metal). It is a graphite (carbon) rod with a copper coating to prolong electrode life.

Electrode The electrodes do get used up during the process, and need to be replaced as needed. More information on ACA electrodes

You need to know: The Width of groove is determined by the diameter of electrode, Depth is dictated by the angle of electrode to the workpiece and rate of travel. Relatively high travel speeds are possible when a low electrode angle is used. This produces a shallow groove.

More to know A steep angle results in a deep groove and requires slower travel speed. Note, a steeply angled electrode may give rise to carbon contamination. The steadiness of the operator determines the smoothness of the surface produced.

Air Carbon Arc Gouging Safety Remove all combustibles from the area. Wear proper protective equipment to protect your body.

More about Safety You need hearing protection, EAR plugs will also keep sparks out of your ears. Wear a welding helmet shade 8 or darker for EYE protection. (it uses an electric ARC like welding). Wear a dust mask to catch particulates. Keep your head out of the fume plume. Ventilate your work area.

The normal Air Carbon Arc cutting safety precautions are similar to shielded metal arc welding. Click on the picture clip to watch a Video clip. ***Then Discuss with the person on your right “Did you notice any safety concerns”?

Air Carbon Arc Gouging More information on operating the ACA Click the picture This shows how the equipment is set up in order to air carbon arc gouge

Polarity A DC power supply with electrode positive polarity is normally preferred for steel and stainless steel. AC with constant current is more effective for cast iron, copper and nickel alloys but special AC type electrodes must be used.

Air supply The gouging torch is normally operated with compressed air. Air supply pressure will be up to 100psi. Usually 3/8 or 1/2 inch inside diameter hose will work.

As long as there is sufficient air flow to remove molten metal, there are no advantages in using higher pressure and flow rates.

Advantages The process is simple to use. It uses the same equipment as the SMAW welding process. It has a high metal removal rate. The gouge profile can be closely controlled.

Advantages continued The air carbon arc process can be used for cutting or gouging in all positions.

Disadvantages The air jet causes the molten metal to be ejected over a large distance. Because of high currents and high air pressures it is VERY noisy. If improperly done it will add carbon to the metal on the groove surface.

Remove carbon pick up Cleaning the groove after gouging is usually done by grinding. It must remove all of the surface carbonized material in the groove joint .

Operation To start a gouging or cutting operation, the operator starts the air flow then strikes an arc. The electrode is pointed in the direction of travel with a push angle approximately 45º with the axis-of the groove. Unlike SMAW welding the electrode tip is not withdrawn to establish arc length.

Molten metal directly under the electrode tip is immediately blown away by the air stream. The speed of travel, the electrode angle, and the electrode size and current (amperage) determine the groove depth. Electrode diameter determines the groove width.

Oscillating the electrode in a circular or restricted weave motion during gouging can greatly increase gouging width which is good if the imperfection that is wider than the electrode. Position the electrode to keep the torch 7 inches or less from the metal being gouged for best results. 7 inches

Choose the Amperage range.

PROCESS VARIABLES Like any thermal-cutting process, air carbon-arc gouging is sensitive to variables in operation. Variables can cause changes in the finished gouge that range from undetectable to unacceptable results.

Here are some variables in air carbon-arc process: Electrode Diameter Determines the size of the groove. Amperage is determined by the diameter of electrode being used. This current flow melts the base metal. Voltage is the pressure behind the amperage, or arc force.

More Variables Air Pressure and Air Flow Rate is the medium for removing molten metal. Travel Speed Determines the depth/quality of a finished groove. Electrode Travel and Work Angle determines groove shape. Arc length Affects metal removal rates and quality of groove.

More Practice = More better For successful gouging you must control the variables keeping them in recommended ranges.

What YOU are going to do!!! Objectives: 1: Set up for Air Carbon arc gouging on carbon steel for your shop assignment. 2: Perform straight gouging operations on carbon steel. 3: Remove a Weld by gouging it out on carbon steel. FOLLOW SAFE PRACTICES!

When you are done Bring “COOLED” completed parts to your Teacher for Evaluation and grading.