welding machine

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Arc welder

A welding apparatus is to objects due to heat a device cohesively to add a component to be coated or a solid homogeneous to split into a plurality of object items. In addition to the introduction of heat, the welding machine also exerts force on the components to be welded in many cases, sometimes with a specific sequence of movements.

The technique of welding is mainly used for metals and plastics , whereby various methods of heat generation are used.

Autogenous welding machine

When oxy-fuel welding with ethyne (common name acetylene) and oxygen , an oxy-fuel welding device, also called a welding torch, is used. With the ignited acetylene-oxygen gas mixture emerging from the device nozzle, a flame is generated as a heat source. This melts a welding wire fed in by hand, with the melt of which iron parts are connected.

The welding torch consists of the handle with the connections and regulating valves for the gases and with exchangeable torch nozzles according to the thickness of the workpieces to be welded. Hoses lead from the gas connections to the gas bottles (pressure vessels). Until the late 1950s, the so-called carbide or acetyl developers were common, in which the ethyne was produced from calcium carbide by adding water, then the much simpler use of acetylene in bottles became generally accepted.

In the mixing tube of the handle, the fuel gas is sucked in by the oxygen flowing out under higher pressure and both are fed into the burner nozzle. There the gases burn after ignition with an igniter in the form of a jet flame. The supply of both gases can be regulated individually through the valves. With the so-called cutting torch , additional pure oxygen is blown onto the machining surface by the heating flame, which melts due to the heat and oxidizes to slag due to the excess of oxygen.

To avoid mixing up the hoses, red hoses are used for the fuel gas and blue hoses for oxygen. In addition, the connection for the oxygen hose has a smaller inside diameter than the connection for the fuel gas hose with the same outer diameter. The union nuts have a 3/8 "left-hand thread with notches in the union nut for the fuel gas and a 1/4" right-hand thread for oxygen.

Propane is unsuitable for gas fusion welding because the combustion rate is too low, but is used as an inexpensive fuel gas for coarse flame cutting, such as cutting up scrap.

Arc welder

With the arc welder, the required heat is generated by an electric current in an arc .

MSG welding machine

Metal shielding gas welding devices can be used for metal active gas or metal inert gas welding, depending on the type of shielding gas. In the metal active gas process, or MAG process for short , an arc is created between a wire electrode fed by the machine and a workpiece . To the current contact tube is an inert gas to the melt from the negative effects of protecting the air atmosphere supplied through the gas nozzle. Oxygen and CO 2 are used as active components of the protective gas for argon . The mixing ratio of argon to active gases, especially CO 2 , determines the shape and depth of the penetration and the droplet transfer of the additive. High-alloy CrNi steels can also be MAG welded. If CO 2 is used as the active gas here , the proportion must be limited to a maximum of 5% CO 2 in order to avoid the absorption of carbon in the melt. The consequence would be corrosion.

The metal inert gas process, or MIG process for short , works in a similar way to the MAG process, but the shielding gas does not take an active part in the welding process, but only serves as protection against oxidation. The MIG process is mainly used for high-alloy steels (CrNi steels) and non-ferrous metals. Argon or argon-helium mixtures are used as protective gas. MIG welding is also used for low-alloy steels. The power source required for this must meet various requirements. A family of characteristics with a slightly falling voltage curve has proven to be ideal (2–4 volts falling per 100 amperes). With a minimum welding current of 60–70 amperes, a voltage of approx. 16 volts is assigned. In order to achieve low-spatter welding (spatter-free is almost impossible), the power source must have a certain circuit inductance. The chokes mostly used for this have a twofold effect in the short arc range (approx. 60–200 amps). There

  1. it limits the current at the contact between wire electrode and workpiece,
  2. and stores energy for the subsequent arc phase.

This process is repeated 30–80 times per second, depending on the setting. In the second area (spray arc from approx. 250 amps) there is no mechanical contact between the wire electrode and the workpiece (except when starting).

There are also cored wire welding devices that contain the shielding gas in the tubular wire .

TIG welding machine

In tungsten inert gas welding ( TIG welding ), the arc burns between a non-melting tungsten electrode and the workpiece in an inert protective gas atmosphere. Argon, helium and their mixtures are used as protective gases.

Resistance pressure welding machine

In resistance pressure welding , the workpieces to be joined are pressed together and a high current flows through them. The metal melts at the junction. This process is based on Joule's law (electric heat). A spot welding device essentially consists of a device for generating force (in the form of a stand machine or pliers) and a transformer together with a control for setting the welding current and the timing. A roller seam welder works on the same principle, but can also produce seams through the rollers.

Ultrasonic welder

Ultrasonic welding is a form of friction welding , mainly for the connection of thermoplastic plastics ( thermoplastics is used). One of the parts to be connected is firmly clamped in place while the other part is vibrated by an ultrasonic resonator and simultaneously pressed onto the stationary part. At the contact point, the molecules of the materials are set in vibration, which leads to a material bond between the materials.