The welding methods commonly used in the manufacture of amusement equiment include electrode arc welding, gas shielded welding and submerged arc welding.

1)Characteristics of electrode arc welding Electrode arc welding is a welding method that uses the arc heat between the electrode and the weldment to melt the electrode and part of the weldment to form a weld.During the welding process, the electrode coating melts and decomposes to generate gas and slag. Under the protection of the gas and slag, the harmful effects of the surrounding air on the molten metal can be effectively eliminated.Through the metallurgical reaction between the molten metal and the slag at high temperature, the weld metal is reduced and purified to obtain a high-quality weld.

Electrode arc welding equipment is simple, easy to operate and easy to maintain:Flexible process and strong adaptability, suitable for welding in various indoor and outdoor locations, it can weld carbon steel, low alloy steel, heat-resistant steel, stainless steel and other materials；Compared with gas welding, the quality is good;Easy to control deformation and improve stress by process adjustment.The disadvantage of electrode arc welding is that the production efficiency is low, the labor intensity is high, and the technical level and operation requirements of the welder are relatively high.。

2）Electrode arc welding amusement equipment AC welding machine, rotary DC welding machine and silicon rectifier welding machine are the normally electrode arc welding power sources.AC welding machine is also called AC welding transformer, which is the most widely used power supply equipment in electrode arc welding.Simple structure, low cost, high efficiency, energy saving and easy to use and maintenance are the characteristics of it.

The rotary DC welding machine is composed by a motor and a motor group which support the motor,the AC network provide power to rotate it and drive the motor armature rotate to supply DC power to support welding .The welding current can be adjusted uniformly in a wide range to meet the requirements of the welding process, and the arc combustion is stable。

Silicon rectifier DC welding machine, also known as electrode arc welding rectifier, is an electrode arc welding equipment that converts power frequency alternating current into direct current.Compared with the rotary DC welding machine, it has the advantages of low noise, high efficiency, less material and low cost.

Being stable is a character of the DC welding machine,so we usually will select it when we using small current .And we also will use DC when we weld the alloy steel and stainless steel . There is positive connection and reverse connection for DC .Positive connection is that the workpiece is connected to the positive electrode and the electrode is connected to the negative electrode ,or it is in return.

3）Types of electrode arc welding electrodes.The melting electrode used for electrode arc welding with coating is called electrode. It composed by the solder core and the coating.

Electrodes can be divided into carbon steel electrodes, low alloy steel electrodes, stainless steel electrodes, chrome and chrome molybdenum heat-resistant steel electrodes, low temperature steel electrodes, surfacing electrodes, aluminum and aluminum alloy electrodes, nickel and nickel alloy electrodes, copper and copper electrodes according to their application,alloy electrode, cast iron electrode and special purpose electrode, etc.

According to the acidity and alkalinity of the slag formed by the melting of the electrode coating, it can be divided into two categories: basic electrodes (slag alkalinity >1.5) and acid electrodes (slag alkalinity <1.5).

The loss of alloying elements in the coating is large during the burning when the acid electrode is applied, the oxygen and nitrogen content of the weld metal is high, so the mechanical properties (especially the impact toughness) of the weld metal are low.；The acid slag is difficult to desulfurize and deacidify, so the crack resistance of the electrode is poor; the acid slag is sticky, and the viscosity of the slag increases slowly during the cooling process, which is called “long slag”.However, as the process properties of welding rod is good and the forming is beautiful ,what’s more ,its resistance to porosity so strong because of its poor sensitive for rust, oil, moisture, etc.Acid electrodes are widely used for general structural welding。

Alkaline electrodes have sufficient deoxidizing ability.Alkaline slag has good fluidity, and the viscosity of the slag increases rapidly during the cooling process, which is called “short slag”.The biggest characteristic of basic electrodes is its lower  hydrogen content in the weld metal, so it is also called “low hydrogen electrode”.Some components in the coating of alkaline electrode can effectively desulfurize and dephosphorize , so its crack resistance is good, as well as the mechanical properties of the weld metal, especially the high impact toughness .Alkaline electrodes are mostly used for welding important structures,and it will usually use on amusement equipment.

The disadvantage of basic electrodes is that they are sensitive to rust, oil and moisture, and are prone to porosity defects in the weld.；The stability of the arc is poor and it usually will on DC welding ,but it will be used on AC when you add the coating in  arc stabilization composition ；The slag removal is not good when welding in deep grooves；You have to strength the ventilation during the welding because of its large amount of dust .

4）Specification for electrode arc welding.Welding specification is a general term for each welding parameter of welding quality and welding productivity.In electrode arc welding, the welding specification mainly includes welding current, arc voltage, electrode type and diameter, welding machine type and polarity, welding speed, number of welding layers, etc.。

①Welding current.Welding current is one of the main factors to affect the welding quality and production efficiencyIncreasing the current can increase the penetration depth of the weld and improve the productivity, but the welding core will overheat, the coating will fall off, and it also will defects such as undercut, burn through, and weld bead to changes if the current is over large ；But it will cause incomplete penetration and slag inclusion ect if the current is too small.

②Arc voltage.The arc voltage mainly affects the melting width of the weld, the higher the voltage, the greater the melting width.The arc voltage is determined by the arc length, the arc voltage is high when the arc is long, and the arc voltage is low when the arc is short.20~25V。The arc should not be too long during electrode arc welding, so the arc voltage is not high and the range of variation is not large, generally 20~25V

③Electrode diameter.The diameter of the electrode is mainly selected according to the thickness of the workpiece to be welded: the thinner the workpiece, the thinner the electrode used.；The thicker the workpiece, the thicker the electrode used. Electrodes with a diameter of 3 to 5 mm are the most widely used。

④Welding speed.Welding speed refers to the speed at which the electrode moves in the welding direction.Usually the speed of electrode arc welding will not specified ,and the welder will control it by size of the weld and the characteristics of the electrode .

⑤Welding layers. Multi-layer welding should be used arc welding of medium and thick steel plates, with the layer increase ,the plasticity and toughness of the welded will be improving in the same thickness steel .The layer of welding is determined by practical and experience ,usually will be the ratio of the thickness of the steel  to the diameter of the electrode (integer)

5） Gas protection .Gas shielded welding is a welding method that uses gas to protect the droplet and molten pool metal from the action of air. Commonly used shielding gases are inert gases (such as argon and ammonia), reducing gases (such as ammonia), oxidation Sexual gases (such as carbon dioxide).Base on these protective gases during the welding process, a local gas protective layer is formed around the arc to prevent the intrusion of harmful gases to the molten droplets and molten pools, and to ensure that the welding process tends to be stable.It belongs to open arc operation, and the welding quality is easy to control.Because the shielding gas compresses the arc column, the arc heat is concentrated, and the molten pool volume is small, so the welding heat affected zone and welding deformation are smaller than other arc welding and gas welding.

In the meantime,the slag removal process will be omitted because there is no slag in welding, which will reduce the auxiliary labor to achieve automation and mechanization and improve work efficiency ,reduce the cost . According to the type of shielded gas welding, the most widely used gas shielded welding in practice are argon arc welding and CO2 gas shielded welding.

Mixed gas shielded welding is also being used more and more widely, especially in amusement park、amusement rides、family rides、carnival fair rides、amusement equipment etc .

1）TIG welding.TIG welding is an arc welding method by using argon gas as a protective gas.The arc occurs between the electrode and the weldment, and argon gas is passed around the arc to form a continuous closed multi-argon gas flow to protect the arc and the molten pool from the air.Argon will not chemically interact with metal, and will not dissolve in liquid metal even under high temperature, so the quality of welding is high.Argon arc welding can be divided into two types according to melted of electrode : non-melting electrode argon arc welding and melting electrode argon arc welding.

Non-melting electrode argon arc welding usually called tungsten electrode argon arc welding. It uses a tungsten rod as an electrode,apply on the arc heat generated between the tungsten electrode and the work piece melts the base metal for welding under the protection of argon gas.You can add filler wire if necessary. In the welding process, the tungsten electrode does not undergo obvious melting and consumption, and only plays the role of emitting electrons to ignite the arc and conduct current.TIG welding has a stable arc and can weld thin plates with low current.

Under the protection of argon gas ,melting electrode argon arc welding uses a continuously fed welding wire as an electrode, the base metal and the welding wire are melted to form a weld by the arc heat generated between the welding wire and the workpiece 3mm；The chemical composition of the welding wire used in argon arc welding should be the same as the base metal, and the diameter of the welding wire is generally less than 3mm;The argon used is generally supplied in bottles and sent to the welding area through pipes and nozzles. The purity of argon is required to be bigger than 99.95%.

The advantages of argon arc welding are that the welding quality is excellent, and suitable for welding various steels, non-ferrous metals and alloys; the arc and molten pool are protected by gas, which is clearly visible and facilitates the realization of all-position automatic weldingThe welding speed is fast, the heat affected zone is small, and the welding deformation of the workpiece is small; the arc is stable, the spatter is small, the welding seam is dense, and the shape is beautiful.The disadvantage of argon arc welding is that the equipment and control system of argon arc welding are complicated, and the cost of argon gas is more expensive, but the production efficiency of tungsten argon arc welding is lower..Argon arc welding can be used in various welding joint forms, but the protective effect of argon gas is different under different joint forms. For butt joints and T-shaped joints, argon gas flow has a good protective effect.The air is easy to intrude into the weld area,because the protection effect of the fillet joint is poor .So we should preload the baffle to improve the protection effect of the argon flow .