Exercise 4 Discuss in the group advantages and disadvantages of soldering and brazing metals compared with electric welding methods

UNIT 10

Exercise 1 Read and translate the text into Ukrainian:

Geometry OF Welding

Welds can be geometrically prepared in many different ways. The five basic types of weld joints are the butt joint, lap joint, corner joint, edge joint, and T-joint. Other variations exist as well—for example, double-V preparation joints are characterized by the two pieces of material each tapering to a single centre point at one-half their height. Single-U and double-U preparation joints are also fairly common—instead of having straight edges like the single-V and double-V preparation joints, they are curved, forming the shape of a U. Lap joints are also commonly more than two pieces thick—depending on the process used and the thickness of the material, many pieces can be welded together in a lap joint geometry.

Often, particular joint designs are used exclusively or almost exclusively by certain welding processes. For example, resistance spot welding, laser beam welding, and electron beam welding are most frequently performed on lap joints. However, some welding methods, like shielded metal arc welding, are extremely versatile and can weld virtually any type of joint. Additionally, some processes can be used to make multipass welds, in which one weld is allowed to cool, and then another weld is performed on top of it. This allows for the welding of thick sections arranged in a single-V preparation joint, for example.

After welding, a number of distinct regions can be identified in the weld area. The weld itself is called the fusion zone—more specifically, it is where the filler metal was laid during the welding process. The properties of the fusion zone depend primarily on the filler metal used, and its compatibility with the base materials. It is surrounded by the heat-affected zone, the area that had its microstructure and properties altered by the weld. These properties depend on the base material's behaviour when subjected to heat. The metal in this area is often weaker than both the base material and the fusion zone, and is also where residual stresses are found.

 

Exercise 2 Comprehension check. Answer the following questions:

1 How many basic types of weld joints are there? What are they?

2 What welding methods can weld virtually any type of joint?

3 How is called the weld itself?

4 What do the properties of the fusion zone depend on?

5 What is the heat-affected zone?

 

Exercise 3 Infinitive constructions. Translate the following sentences into English using infinitive complexes.

1 Вважають, що зварювальні роботи в недалекому майбутньому будуть виконувати роботи.

2 Відомо, що ковальська зварка – єдиний зварювальний метод, яким користувалися ковалі до кінця 19 століття.

3 Вчені сподіваються, що скоро буде винайдений новий, ефективний спосіб зварки у відкритому космосі.

 

Exercise 4 Give Ukrainian equivalents of the following:

· butt joint;

· lap joint;

· corner joint;

· edge joint;

· fusion zone;

· filler metal;

· heat-affected zone.

 

 

TEXTS FOR ADDITIONAL READING:

Arc Welding Hazards

▲The symbols shown below are used throughout this manual to call attention to and identify possible hazards. When you see the symbol, watch out, and follow the related instructions to avoid the safety information given below is only a summary of the more complete safety information found in the Safety Standards listed in Section 1 -7. Read and follow all Safety Standards.

▲Only qualified persons should install, operate, maintain, and repair this unit.

▲During operation, keep everybody, especially children, away.

 

ELECTRIC SHOCK CAN KILL


 

Touching live electrical parts can cause fatal shocks or severe burns. The electrode and work circuit is live whenever the output is on. The input power circuit and machine internal circuits are also live when power is on. In semiautomatic or automatic wire welding, the wire, wire reel, drive roll housing, and all metal parts touching the welding wire are electrically live. Incorrectly installed or improperly grounded equipment is a hazard.

· Do not touch live electrical parts.

· Wear dry, hole-free insulating gloves and body protection.

· Insulate yourself from work and ground using dry insulating mats or covers big enough to prevent any physical contact with the work or ground.

· Do not use AC output in damp areas, if movement is confined, or if there is a danger of falling.

· Use AC output ONLY if required for the welding process.

· If AC output is required, use remote output control if present on unit.

· Additional safety precautions are required when any of the following electrically-hazardous conditions are present: in damp locations or while wearing damp clothing; on metal structures such as floors, gratings or scaffolds; when in cramped positions such as sitting, kneeling or lying, or when there is a high risk of unavoidable or accidental contact with the workpiece or ground. For these conditions, use the following equipment in order presented: 1) a semiautomatic DC constant voltage (wire) welder, 2) a DC manual (stick) welder, or 3) an AC welder with reduced open-circuit voltage. In most situations, use of a DC, constant voltage wire welder is recommended. And, do not work alone!

· Disconnect input power or stop engine before installing or servicing this equipment. Lockout/tagout input power according to OSHA 29 CFR 1910 147 (see Safety Standards)

· Properly install and ground this equipment according to its Owner's Manual and national, state, and local codes.

· Always verify the supply ground —check and be sure that input power cord ground wire is properly connected to ground terminal in disconnect box or that cord plug is connected to a properly grounded receptacle outlet.

· When making input connections attach proper grounding conductor first – double-check connections.

· Frequently inspect input power cord for damage or bare wiring — replace cord immediately if damaged — bare wiring can kill.

· Turn off all equipment when not in use.

· Do not use worn, damaged, undersized, or poorly spliced cables.

· Do not drape cables over your body.

· If earth grounding of the workpiece is required, ground it directly with a separate cable.

· Do not touch electrode if you are in contact with the work, ground, or another electrode from a different machine.

· Use only well-maintained equipment. Repair or replace damaged parts at once. Maintain unit according to manual.

· Do not touch electrode holders connected to two welding machines at the same time since double open-circuit voltage will be present.

· Wear a safety harness if working above the floor level.

· Keep all planes and covers securely in place.

· Clamp work cable with good metal-to-metal contact to workpiece or worktable as near the weld as practical.

· Insulate work clamp when not connected to workpiece to prevent contact with any metal object.

· Do not connect more than one electrode or work cable to any single weld output terminal.