Flame cutting ,types and process

As we have discussed earlier, Flame cutting is a process of   Oxygen cutting and. . It is affected by, the chemical reaction of oxygen with the base metal at elevated temperatures.  
 

 
Flame cutting

The flame cutting process is also called the oxy-fuel gas cutting process and is mainly used in two ways:

1.  By manual flame cutting process, 
2. By machine flame cutting process.

Manual or Hand Flame Cutting

Manual flame cutting is fully operated upon the skill of the operator, in this process, the torch is held and guided by the operator, it gives less accuracy and smoothness as compared to machine flam cutting. However, manual cutting can be used with serviceable accurateness on thicknesses up to 200 to 300mm.

The consumption of oxygen is usually much greater in manual cutting than in machine cutting, it is widely employed on production jobs and in scrapping operations

Machine flame cutting.

Machine cutting machines are designed to hold the torch(or torches)in specific predetermined positions, it provides greater speed, accuracy, and economy. These types of machines are preferred when materials to be cut in large amounts. The flame cutting machine may be categorized as follows:

Portable (transportable) machine 

Generally, a portable system includes a variable speed driven motor carriage with an adjustable mounting for the torch. the device generally travels on a track, which guides to the torch.

To function ignites the torch positions it at the beginning point, adjust torch height above the work floor to be cut, initiates cutting oxygen flow and carriage travel. At the end of the cutting, shut off the carriage and cutting torch. Maximum transportable machines are made to work both on a line or in a circular track. numerous sized circles can be cut through the putting made on a radius-rod attachment.

Cutting machine

Stationary Machines

Static machines are much heavier and larger than portable machines. These machines mainly cut plates into straight-line cuttings or strips, plate edge preparations for welding purposes, bevel cuts from these machines can easily be made by tilting the torch at the desired angle.

Stationary machines remain in a fixed location, a machine in the workshop, a system to supply oxygen and acetylene, and a material handling system. The torch support train runs on the track. The cutting machine structure either expands the work with a gland. Type bridge across tracks or it can be cantilevered from one side of the tracks.

Shape cutting

Shape cutting refers to any regular or irregular contour cutting of metal. Shape cutting of metal. Shape cutting machines are of two types, a pantograph and a cross-carriage mechanism type.In both these machines the basic element is a floating bar with one or more torches located on one end and a tracing or driving device on the other.

In the cross carriage type, the carriage rides on the rails. The bar holding the torches can be easily moved at right angles to the carriage on which it rides. In the pantograph machine, the bar is held by two arms that fold open and shut. The complete pantograph assembly is mounted on a carriage riding on rails.

A shape cutting machine has to make use of tracing devices, as listed below, to guide it to cut different shapes:

Magnetic tracer

The amagnetic tracer adheres to and follows the outline of a steel template. The workpiece gets cut to the same shape as that of the template. Big gears may be cut from the plates by using a magnetic tracer.

Photoelectric tracer

A photoelectric tracer, which in essence, is an electric eye, follows the outline of a pencil or ink sketch of an intricate shape and guides the driving wheel. Traction for driving the machine comes solely from the driving wheel.

Metals cut by Flame Cutting

·         Carbon steel and low alloy steels, Cast iron,  Wrought iron,   High alloy, and stainless steel

·        Advantages of Flame cutting

• This process is faster than mechanical cutting methods and costs less than machine cutting machines such as mechanical cutting machines.
• Shapes and sizes machined by mechanical means can be cut easily by cutting flame.
• Flame cutting equipment, being portable, can be easily used for fieldwork
• Multi-torch machines can cut multiple pieces at once.

Disadvantages of Flame cutting

• · Flame cutting is limited to the cutting of steel and cast iron.
• As compared to mechanical cutting, the dimensional tolerances are poor.
• The area of cutting needs adequate ventilation and proper fume control.
• The expelled red hot slag and other particles produced fire and burning risk to plants and workers.

·        Uses and applications

To prepare edges for bevel and groves of the weld joint.

To cut small-sized workpieces from bigger plates for further processing, cut rivets, gates, and risers from castings. cutting many layers of thin sheets at the same time(stack cutting)to reduce both time and cost for production works. pierce holes and slots in steel plates, for salvage works.