**3. Design of technological equipment for hybrid processes**

The peculiarities of HLAW process lead to specific requirements for technological equipment for this process. Development of technological hybrid welding equipment is easier using the block-module approach. It allows inheritance in design and interoperability and also decreases development time. According to this approach, each installation includes laser power source, arc source, special welding tool, system of control, cooling system, gas distribution system, welding parts manipulator, seam tracking system, and process monitoring system. Joining of subsystem is provided by common interfaces for control, mechanic connecting, gases, and water. Using this approach, a number of machines have been designed for industry; some of these are described below.

First, technological installation, which we describe below in details, has been developed for hybrid laser-MAG welding of oil and gas pipes of large diameter (**Figure 16**). It provides welding of pipe steel with thickness of more than 12 mm together by one pass with a speed of up to 3 m/min. Simulation with LaserCAD allowed to determine parameters of installation for this purpose: laser source power is not less than 15 kW; beam diameter in focus is 0.3–0.4 mm; welding current is not less than 250 A; and diameter of the electrode wire is in range of 1–2 mm.

**Figure 16.** Hybrid welding equipment.

This hybrid laser-arc complex contains: IPG fiber laser LS-15, arc power source with current of up to 1500 A, and numerical control filler wire feeding equipment, special working tools, CNC module of preparation, and distribution of used gases, monitoring system of the welded joint, tracking system with scanner laser sensor, process monitoring system, and control system.

rate range toward lower frequencies. Long (*S*1) and short (*S*2) waves have the highest frequency range to 10 kHz. These spectra also depend on the cavity depth. The increase of feeding velocity also decreases the low-frequency oscillations. The same approach can be used for analysis of

The peculiarities of HLAW process lead to specific requirements for technological equipment for this process. Development of technological hybrid welding equipment is easier using the block-module approach. It allows inheritance in design and interoperability and also decreases development time. According to this approach, each installation includes laser power source, arc source, special welding tool, system of control, cooling system, gas distribution system, welding parts manipulator, seam tracking system, and process monitoring system. Joining of subsystem is provided by common interfaces for control, mechanic connecting, gases, and water. Using this approach, a number of machines have been designed for industry; some of

First, technological installation, which we describe below in details, has been developed for hybrid laser-MAG welding of oil and gas pipes of large diameter (**Figure 16**). It provides welding of pipe steel with thickness of more than 12 mm together by one pass with a speed of up to 3 m/min. Simulation with LaserCAD allowed to determine parameters of installation for this purpose: laser source power is not less than 15 kW; beam diameter in focus is 0.3–0.4 mm; welding current is not less than 250 A; and diameter of the electrode wire is in range of 1–2

**3. Design of technological equipment for hybrid processes**

porosity and spiking appearance (**Figure 15**).

these are described below.

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**Figure 16.** Hybrid welding equipment.

mm.

This module is used in complex welding of metallic workpieces with a possible gap of up to 2 mm, MAG torch is installed in front of the laser. This complex mainly includes positions already mentioned above.

Stabilization of the hybrid module position and control is described in more detail in [2]. Precision of keeping the focus point position of the laser head relative to welded blanks in the vertical direction is ±0.2 mm, and in the cross-section direction is ±0.5 mm.

The control system of hybrid laser-arc complex is developed as a hardware-software complex. Present system controls the components of the complex. The system includes a control subsystem forming welds subsystem monitoring and automatic control system.

It provides reading profile blanks geometry control, tracking the welding process at speeds of up to 6 m/min, the welding head positioning, control of the laser source, the control operation of the arc, and gas control system. The system also has a built-in protection against harmful conditions and operational control using the monitoring system.

Development of the control and monitoring systems for process of laser-arc welding is still a relevant task. Using of such systems is essential for the adoption of these technologies into the industry.

To solve this problem, it is necessary to carry out researches of the weld pool dynamics and also define basic mechanisms of defects formation specified for welding with deep penetration. For developing this system, secondary emission signals coming from laser-arc action zone were also analyzed and sensors for their registration were included.

The monitoring system, designed for HLAW, is based on registration of optical emission in different spectral ranges, depending on the range [5]. Sensors are installed in two directions and are equipped with a video camera. It simplifies the guidance process and allows tracing the spatial variation of the active zone. Synchronous registration, processing, and recording of signals are realized by using developed software.

Series of experiments on welding of model samples was carried out for verifying the moni‐ toring system. Test results confirm the possibility of weld formation monitoring using the multisensor monitoring system (**Figure 17**). The presented results confirm the ability to monitor porosity level in weld using the developed system.

However, to use the monitoring system in real production it requires further research aimed at understanding the characteristics of particular process [28], identifying typical process defects, and adaptation monitoring system for this technological process.

Hybrid technology permits to create mobile technological equipment, which is able to perform

Laser and Hybrid Laser-Arc Welding http://dx.doi.org/10.5772/64522 145

Control and stabilization of position of the hybrid laser-arc module relative to the joint is fulfilled by linear drives system installed on moving platform. It operates the same way as the

Another example of HLAW machine, based on the same design approach, is robot-based

Robot-based scheme of machine allows to weld parts of up to 4 m in length in different space

There are several fields of applications [31], in which usage of HLAW is especially prospective. First of them is production of large diameter pipes for oil and gas. The technology for different

thickness of pipe walls was designed and the examples are shown in **Figure 20**.

all spectra of process advantages.

**Figure 18.** Mobile hybrid orbital system.

**Figure 19.** Robot-based HLAW machine on the base of 25 kW fiber laser.

installation (**Figure 19**).

positions.

**4. Technology of HLAW**

stationary machine.

**Figure 17.** Signal response of the coaxial plasma sensor to change the level of porosity. X-ray photograph of the weld. Distribution of the pores area along the weld. Coaxial plasma signal.

For solving problems, the control system consists of several subsystems: laser control; arc equipment control; gas equipment control; welding head stationing; determination of the metal joint geometry; the control of parameters and protection of the laser welding head; the central controller module; and operating computer. For communication with other modules of the complex a card of CAN interface is put in the computer.

Other HLAW system [29], shown in **Figure 18**, based on soft direction belt, on which a motion unit with hybrid module, seam tracking, and filler wire feeding are mounted. Another subsystem is located in the stationary unit. In the equipment, 20 kW fiber laser with two direction switches is used. It allows to weld two joints in one time. This system uses a new inverter arc source. A used subsystem has a number of design features, for example, tracking sensor operating at high power in welding, and with a high degree of reflected radiation. However, they require special processing techniques of received signals [30]. Monitoring system for providing quality control process should capture the emergence of various defects (porosity, humping) [28]. The control system of this complex is implemented on the same base as the previous one.

Hybrid technology permits to create mobile technological equipment, which is able to perform all spectra of process advantages.

Control and stabilization of position of the hybrid laser-arc module relative to the joint is fulfilled by linear drives system installed on moving platform. It operates the same way as the stationary machine.

**Figure 18.** Mobile hybrid orbital system.

**Figure 17.** Signal response of the coaxial plasma sensor to change the level of porosity. X-ray photograph of the weld.

For solving problems, the control system consists of several subsystems: laser control; arc equipment control; gas equipment control; welding head stationing; determination of the metal joint geometry; the control of parameters and protection of the laser welding head; the central controller module; and operating computer. For communication with other modules

Other HLAW system [29], shown in **Figure 18**, based on soft direction belt, on which a motion unit with hybrid module, seam tracking, and filler wire feeding are mounted. Another subsystem is located in the stationary unit. In the equipment, 20 kW fiber laser with two direction switches is used. It allows to weld two joints in one time. This system uses a new inverter arc source. A used subsystem has a number of design features, for example, tracking sensor operating at high power in welding, and with a high degree of reflected radiation. However, they require special processing techniques of received signals [30]. Monitoring system for providing quality control process should capture the emergence of various defects (porosity, humping) [28]. The control system of this complex is implemented on the same base

Distribution of the pores area along the weld. Coaxial plasma signal.

as the previous one.

144 Joining Technologies

of the complex a card of CAN interface is put in the computer.

Another example of HLAW machine, based on the same design approach, is robot-based installation (**Figure 19**).

**Figure 19.** Robot-based HLAW machine on the base of 25 kW fiber laser.

Robot-based scheme of machine allows to weld parts of up to 4 m in length in different space positions.
