Seam Welding Machines

Higher welding forces will be needed for harder alloys and lower values for softer alloys. Welding parameters for three phase frequency converter units are similar to those in Table 9.4 except that welding current needs to be increased by between 0.5 and 2.5 times, the higher values for the thicker materials.

Pick-up on the electrode wheel can be a problem and may require the wheel to be cleaned after only one revolution. Mechanised cleaning systems that remove the contamination in-process by wire brushing or abrasive means have been successful in maintaining continuous production.

Seam welding is used in the same way as spot welding, and operates on essentially the same principle. The difference is that two wheel-shaped electrodes are used, rolling along (and usually feeding) the work piece

The two wheels should be of the same size, in order to prevent the part from being deflected towards one of them. The actual contact profile can be designed in a number of ways, in order to suit the shape of the part to be welded. The current may flow continuously while welding is being carried out, or intermittently to produce a series of spots that are so closely positioned as to produce a single, continuous weld. An unavoidable problem of seam welding is that some of the current 'leaks' through the completed weld.

As the electrode rollers rotate, they do not need to be lifted between each spot, as with spot welding. If the weld does not have to be continuous, seam welding can be used to position spots at regular distances from each other. That means that seam welding can be carried out quicker than ordinary spot welding.

All the seam-welding techniques require high thermal energy input to weld work pieces together. Contrary to a spot weld, a seam weld is a continuous weld in various welding geometries such as fillet and butt welds. In this chapter, only seam-welded joints are considered, whereas the analysis and behavior of spot-welded joints is a specific area that has been treated differently and will be discussed in Chapter 11.

During the service life of welded structures exposed to various service loading conditions, welded joints are usually the potential fatigue failure sites due to the highest stress concentration areas and altered material properties. Thus, engineers and scientists are always interested in understanding fatigue characteristics of the welded joints, and are trying to develop analytical tools to estimate fatigue lives of welded joints. However, prediction of fatigue life of welded joints is frequently complicated and inaccurate because many parameters affect the fatigue life of welded joints.

Welding strongly affects the materials by the process of heating and subsequent cooling as well as by the fusion process with additional filler material, resulting in inhomogeneous and different materials. Furthermore, a weld is usually far from being perfect, containing inclusions, pores, cavities, undercuts, and so on. The shape of the weld profile and nonwelded root gaps creates high stress concentrations with varying geometry parameters. Moreover, residual stresses and distortions due to the welding process affect the fatigue behavior.

In view of the complexity of this subject on fatigue life prediction models of seam-welded joints and the wide area of applications, it is not surprising that several analytical approaches exist and none of them could account for the aforementioned process variables. Therefore, it has been an ongoing research area of interest to all the engineering disciplines to improve the life predictive capability for seam-welded joints.

Due to the vast amount of relevant literature, this chapter will present only Dong's and Fermer's structural stress approaches (Dong, 2001a,b; Fermer et al., 1998) and the notch pseudo stress approach because the three approaches have been coded in some commercial fatigue analysis modules as one of the Computer Aided Engineering (CAE) tools used in automotive engineering. Refer to the book by Radaj et al. (2006) for a detailed review of all other methods. However, this chapter will start with an introduction of the parameters affecting the fatigue life of welded joints to help you understand the possible sources of the variability of fatigue data.

Special Features

Thyristor controlled electronic timer with electronic heat control, to give heavy duty high speed operation, providing smooth, stepless and accurate adjustment of the welding current.

High quality roller bearings carrying the roller shafts, guaranteed longer-life of the roller heads.

Leak proof joints at much lower costs than conventional welding.

Resistance seam welding is a process that produces a weld at the faying surfaces of two similar metals. The seam may be a butt joint or an overlap joint and is usually an automated process. It differs from flash welding in that flash welding typically welds the entire joint at once and seam welding forms the weld progressively, starting at one end. Like spot welding, seam welding relies on two electrodes, usually made from copper, to apply pressure and current. The electrodes are often disc shaped and rotate as the material passes between them. This allows the electrodes to stay in constant contact with the material to make long continuous welds. The electrodes may also move or assist the movement of the material.

A transformer supplies energy to the weld joint in the form of low voltage, high current AC power. The joint of the work piece has high electrical resistance relative to the rest of the circuit and is heated to its melting point by the current. The semi-molten surfaces are pressed together by the welding pressure that creates a fusion bond, resulting in a uniformly welded structure. Most seam welders use water cooling through the electrode, transformer and controller assemblies due to the heat generated.

Seam welding produces an extremely durable weld because the joint is forged due to the heat and pressure applied. A properly welded joint formed by resistance welding can easily be stronger than the material from which it is formed.

A common use of seam welding is during the manufacture of round or rectangular steel tubing. Seam welding has been used to manufacture steel beverage cans but is no longer used for this as modern beverage cans are seamless aluminum.

There are two modes for seam welding: Intermittent and continuous. In intermittent seam welding, the wheels advance to the desired position and stop to make each weld. This process continues until the desired length of the weld is reached. In continuous seam welding, the wheels continue to roll as each weld is made.

To meet diverse requirements of our clients in the best possible manner, we are offering a comprehensive range of Seam Welding Machine.

Applications: Automobile Products Sheet Metal Components Strip Processing Industries Transformer Radiators Drums, Barrelss, Containers

Specification: Available in circumferential, longitudinal & universal types

Specifications:

Ratings KVA : 50, 75, 100 150, 200.

Construction : Robust construction, streamlined appearance with maximum resistance to deflection. Welding transformer enclosed in the main frame, pneumatic control mounted on the machine.

Welding Transformer: Transformer conforms to IS: 4804 Part-I and RWMA Standards, water-cooled, class 'F' insulation with thermo switch protection for overloading.

Current Control: Welding current adjustable from 50 to 100% by means of a tap change links.

Cooling System: Thyristors, Transformer, Secondary connections and electrode wheels are water-cooled.

Electrode Force: Upper arm is actuated by heavy-duty 2-way pneumatic cylinder, controlled by solenoid valve. Compressed air at 2.0 Kg/cm.sq. to 5.6 kg/cm.sq. provides electrode force. Air filter, lubricator, regulator, pressure gauge are provided as standard accessories.

Electrode Drive: Machines are provided with different drive system depending on the application. Customer to specify the preferred system.

Direct Drive: Direct Gear is given to any one of the wheels

Knurl Drive: One of the Wheels or both are driven through a serrated hardened wheel depending on the style of welding. Constant dressing of weld wheel of maintains uniform profile, constant welding speed irrespective of weld wheel diameter are some of the advantages of knurl drive system.

Narrow Track Seam Welding (Optional at Additional Cost): In order to weld coated sheets for application like fuel tank, machine with narrow track welding (2.5 to 3 mm weld width) facility could also be supplied. In narrow track seam welding, weld wheels are of thickness 6 mm constantly coined for circular profile, which results in narrow contact with very high-pressure density. Due to this high-pressure density the coated material on the sheet metal is squeezed out during the welding.

Motor Drive: Machine will be supplied with drive system comprising AC squirrel cage induction motor, with variable speed AC drive and Reduction GearBox as standard.

Seam Welding Machine is precision built, with careful design and robust construction, suitable for long trouble free service. Each machine is submitted to rigorous proving tests before delivery is made, in order that the machine may be ready for immediate installation and operations at customer's works.

These pneumatically operated seam welding machines are used for an uninterrupted weld run for impeccable seam welding of the drums. Featuring modern design, these seam welding machinesare air operated and have a variety of alternative features for ensuring efficient usage in every kind of seam welding application within the range. We manufacture, supply and export seam welding machines in various specifications to our clients