Figure 2–32PAC schematic.
What are PAC’s advantages?
•PAC cuts all metals.
•Cutting action is so rapid that despite the high heat input, there is a smaller heat affected zone than in most other processes.
•PAC can pierce metals cleanly without the starting hole needed by OAC.
•PAC is ideal for cutting parts under computer-driven control.
•With its 30,000°F (16,600°C) plasma, it cuts materials with melting points too high for OAC.
•All positions can be used.
•Surface smoothness of the cut edges is equal to or better than OAC.
What are the drawbacks to PAC?
•Equipment may be expensive. Small units today are more cost effective than in the past.
•Metal vapor produced from the cutting must be captured.
•Thick cuts are normally done under water so the metal vapor can be captured; the water container must then be periodically cleaned usually requiring a HAZ MAT crew.
What safety rules should be followed?
All of the safety rules suggested in OAC cutting should be applied to PAC including:
•This process used electricity with voltage ranges from 150 to 400 volts of direct current; this equipment must be properly grounded to avoid electric shock.
•Keep electrical circuits dry.
•Keep all mechanical electrical connection tight; this includes the work lead. Poor electrical connection can cause over heating and fires.
•Proper ventilation is required to prevent inhalation of hazardous metal vapors and gases.
•When securing the equipment always be sure the power supply has been properly shut down and the torch placed in back on it’s proper insulated storage position.
Laser Beam Cutting
How does laser beam cutting work and what are its applications?
Laser beam cutting, AWS designation LBC, is a thermal process using laser beam energy to cut materials by melting or vaporizing. A gas is sometimes used to assist in the removal of melted or vaporized material. Cutting and drilling power densities in the range of 6.5 × 106 to 6.5 × 108 W/in2 (104 to 106 W/mm2) are achieved. Lasers can also drill holes using higher power densities and shorter dwell times than when cutting. Hole dimensions range from 0.0001 to 0.060 inches (0.0025 to 1.5 mm). Although a high-power CO2 laser cuts carbon steel up to 1 inch thick (25 mm), good quality cuts are made on material 0.375 inch (9.5 mm) and less in thickness. The depth of focus limits the quality of thick cuts.
What are the advantages of LBC?
•Narrow kerf widths
•High cutting speeds
•High quality edge surfaces
•Low heat input/minimum distortion
•Cuts most materials
•Easily automated
•Repeatable, precision dimensions
•Multiple layers of material may be cut at the same time
What are the drawbacks to LBC?
•Equipment is expensive.
•Replacement lens’ and consumables are expensive.
See Figure 2–33.
Figure 2–33Schematic of a LBC
It is possible to fly without motors, but notwithout knowledge and skill.
Wilbur Wright
Introduction
Soldering has been used for thousands of years, but a solid theoretical understanding has come only in the last one hundred. Brazing is similar to soldering but performed at higher temperatures. It has come into use more recently as higher temperature torches became available. Although soldering and brazing do not make joints as strong as welded ones, they are widely used in making and repairing a wide range of products from airplanes to computers to household plumbing to jewelry. Soldering and brazing processes can be as simple as using a soldering iron, a propane torch or as complex as using radio frequency energy in a vacuum to join parts. We will discuss the theory, materials, fluxes, and common industrial processes. These processes have some advantages over welding and we will present them. There are safety issues too. Because soldering copper water pipe is so useful and something every welder should know how to do, we cover step-by-step instructions in Chapter 15.
Process Names
What is the AWS designation for brazing?
The AWS designation for brazing is B.
What common names are sometimes used for brazing?
Silver soldering, silfloss, and hard soldering are non-preferred names for brazing. Silver brazing filler metals are not solders; they have melting points above 840°F (450°C).
How are brazing processes classified and what are the commercially significant ones?
Brazing processes are classified by heat-source type. Commercially important ones are:
•Dip Brazing (DB)
•Furnace Brazing (FB)
•Induction Brazing (IB)
•Infrared Brazing (IB)
•Resistance Brazing (RB)
•Torch Brazing (TB)
What is the AWS designation for soldering?
The AWS designation for soldering is S.
What are the commercially important soldering processes?
•Dip Soldering (DS)
•Furnace Soldering (FS)
•Induction Soldering (IS)
•Infrared Soldering (IRS)
•Iron Soldering (INS)
•Resistance Soldering (RS)
•Torch Soldering (TS)
•Wave Soldering (WS)
Note that with the exception of iron soldering and wave soldering both brazing and soldering share most common processes.
Process
In general terms how does the brazing process work?
Brazing joins materials that have been heated to the brazing temperature followed by adding a brazing filler metal having a melting point above 840°F (450°C). This temperature will be below the melting point of the base metals joined by this joining process. The non-ferrous filler metal is drawn into and fills the closely fitted mating or faying surfaces of the