CLASSIFICATION OF WELDING AND ALLIED PROCESSES

CLASSIFICATION OF WELDING AND ALLIED PROCESSES

There are different welding, brazing and soldering methods are being used in industries today.

There are various ways of classifying the welding and allied processes. For example, they may

be classified on the basis of source of heat, i.e., blacksmith fire, flame, arc, etc. and the type

of interaction i.e., liquid / liquid (fusion welding) or solid/solid (solid state welding). Welding

processes may also be classified in two categories namely plastic (forge) and fusion. However,

the general classification of welding and allied processes is given as under

(A) Welding Processes

1. Oxy-Fuel Gas Welding Processes

1 Air-acetylene welding

2 Oxy-acetylene welding

3 Oxy-hydrogen welding

4 Pressure gas welding

2. Arc Welding Processes

1. Carbon Arc Welding

2. Shielded Metal Arc Welding

3. Submerged Arc Welding

4. Gas Tungsten Arc Welding

5. Gas Metal Arc Welding

6. Plasma Arc Welding

7. Atomic Hydrogen Welding

8. Electro-slag Welding

9. Stud Arc Welding

10. Electro-gas Welding

3. Resistance Welding

1. Spot Welding

2. Seam Welding

3. Projection Welding

4. Resistance Butt Welding

5. Flash Butt Welding

6. Percussion Welding

7. High Frequency Resistance Welding

8. High Frequency Induction Welding

4. Solid-State Welding Processes

1. Forge Welding

2. Cold Pressure Welding

3. Friction Welding

4. Explosive Welding

5. Diffusion Welding

6. Cold Pressure Welding

7. Thermo-compression Welding

5. Thermit Welding Processes

1. Thermit Welding

2. Pressure Thermit Welding

6. Radiant Energy Welding Processes

1. Laser Welding

2. Electron Beam Welding

(B) Allied Processes

1. Metal Joining or Metal Depositing Processes

1. Soldering

2. Brazing

3. Braze Welding

4. Adhesive Bonding

5. Metal Spraying

6. Surfacing

2. Thermal Cuting Processes

1. Gas Cutting

2. Arc Cutting

TWIST DRILL GEOMETRY.

Twist Drill Geometry
Twist drill geometry and its nomenclature are shown in Fig. 22.5. A twist drill has three
principal parts:
(i) Drill point or dead center
(ii) Body
(iii) Shank.

Drill axis is the longitudinal centre line.
Drill point is the sharpened end of the drill body consisting of all that part which is
shaped to produce lips, faces and chisel edge.
Lip or cutting edge is the edge formed by the intersection of the flank and face
Lip length is the minimum distance between the outer corner and the chisel-edge
corner of the lip.
Face is that portion of the flute surface adjacent to the lip on which the chip impinges
as it is cut from the work.
Chisel edge is the edge formed by the intersection of the flanks.
Flank is that surface on a drill point which extends behind the lip to the following flute.
Flutes are the grooves in the body of the drill, which provide lips, allow the removal of
chips, and permit cutting fluid to reach the lips.
Flute length is the axial length from the extreme end of the point to the termination
of the flutes at the shank end of the body.
Body is that portion of the drill nomenclature, which extends from the extreme cutting
end to the beginning of the shank.
Shank is that portion of the drill by which it is held and driven,
Heel is the edge formed by the intersection of the flute surface and the body clearance.
Body clearance is that portion of the body surface reduced in diameter to provide
diametric clearance.
Core or web is the central portion of the drill situated between the roots of the flutes
and extending from the point end towards the shank; the point end of the core forms the
chisel edge.
Lands are the cylindrically ground surfaces on the leading edges of the drill flutes. The
width of the land is measured at right angles to the flute.
Recess is the portion of the drill body between the flutes and the shank provided so as
to facilitate the grinding of the body. Parallel shank drills of small diameter are not usually
provided with a recess.
Outer corner is the corner formed by the intersection of the lip and the leading edge of
the land.
Chisel edge comer is the corner formed by the intersection of a lip and the chisel edge.
Drill diameter is the measurement across the cylindrical lands at the outer corners of
the drill. .
Lead of helix is the distance measured parallel to the drill axis between corresponding
points on the leading edge of a flute in one complete turn of the flute.
Helix angle is the angle between the leading edge of the land and the drill axis.
Rake angle is the angle between the face and a line parallel to the drill axis. It is bigger
at the face edges and decreases towards the center of the drill to nearly 0°. The result is that
the formation of chips grows more un-favorable towards the centre.
Lip clearance angle is the angle formed by the flank and a plane at right angles to the
drill axis; the angle is normally measured at the periphery of the drill. To make sure that
the main cutting edges can enter into the material, the clearance faces slope backwards in
a curve. The clearance angle is measured at the face edge, must amount to 5° up to 8°.
Point angle is the included angle of the cone formed by the lips.

MACHINE DE FORAGE

MACHINE DE FORAGE

1 INTRODUCTION ..
De forage est une opération de fabrication d'un trou circulaire en enlevant un volume de métal de
le travail en coupant outil appelé foret. Un foret rotatif est une extrémité de coupe-outil avec un ou plusieurs coupe
les lèvres et le plus souvent une ou plusieurs flûtes pour le passage de copeaux et de l'admission de fluide de coupe.
Une machine de forage est une machine-outil destiné à percer des trous dans les métaux. Il est l'un des plus
machines-outils importants et polyvalent dans un atelier. Outre le forage des trous ronds, de nombreux
d'autres opérations peuvent également être effectuées sur la machine de forage tels que contre-ennuyeux,
fraisage, rodage, alésage, rodage, sablage, etc
2 CONSTRUCTION DE MACHINE DE FORAGE
Machine de forage dans le forage est mis en rotation et recevant le long de son axe de rotation fixe dans l'
pièce. Différentes parties d'une machine de forage sont discutés
ci-dessous: (i) La tête contenant un moteur électrique, V-poulies à courroie en V et qui transmettent rotatif
mouvement de la broche de perçage à un certain nombre de vitesses. (Ii) de la broche est constituée d'acier allié. Il
tourne ainsi que se déplace de haut en bas dans un manchon. Un pignon en prise avec une crémaillère fixée sur le
manchon pour fournir un mouvement vertical de haut en bas de la broche et donc du forage, de sorte que le
même peut être introduit dans la pièce à usiner ou en être retirés lors du forage d'. Vitesse de rotation ou de la
vitesse de la perceuse est changée avec l'aide de la courroie trapézoïdale et V-beaux-poulies. Les grandes machines de forage sont
ayant boîtes de vitesses dans le but déclaré. (Iii) de mandrin de forage est maintenu à la fin de la broche de perçage
et à son tour, contient le trépan de forage. (Iv) réglable table de pièce à usiner est supporté sur la colonne
de la machine de forage. Il peut être déplacé à la fois verticalement et horizontalement. Les tables sont généralement
comportant des fentes de telle sorte que l'étau ou de la pièce peut être solidement tenue à ce sujet. Table de base (v) est
un casting lourd et il prend en charge la structure de la perceuse. La base supporte la colonne, qui
à son tour, prend en charge la table, la tête etc (vi) la colonne est une tour verticale ou caisson qui repose
sur la base et supporte la tête et la table. La colonne ronde peut avoir des dents de crémaillère coupé
sur lui afin que la table peut être soulevé ou abaissé en fonction des exigences de pièce.
Cette machine se compose de pièces suivantes
1. Base
2. Pilier
3. Entraînement principal
4. Percer la broche


3 TYPES DE MACHINE DE FORAGE
Machines de forage sont classés sur la base de leurs caractéristiques de construction, ou le type
de travail qu'ils peuvent manipuler. Les différents types de machines de forage sont les suivants:
(1) Perceuse portable
(2) machine de forage sensible
(A) Banc de montage
(B) de montage au sol
(3) machine de forage vertical
(A) section de la colonne ronde
(B) la machine la section Boîte colonne
(4) Perceuse radiale
(A) Plaine
(B) Semiuniversal
(C) universelle
(5) machine de forage Gang
(6) machine à multiple de forage de broche
(7) Perceuse automatique
(8) Machine à perçage profond
(A) verticale
(B) Horizontal
Peu de machines de forage couramment utilisées sont décrites au titre:



1 perceuse portative
Une machine de forage portatif est une petite unité compacte et utilisé pour percer des trous dans worpieces
dans n'importe quelle position, qui ne peut pas être foré dans une machine de forage standard. Il peut être utilisé pour
percer des trous de petit diamètre dans les pièces moulées ou pièces soudées de grandes à cet endroit même où ils
sont couchés. Perceuses sont équipés de petits moteurs électriques, qui peut être
motivée par la nécessité et l'alimentation A.C. D.C.. Ces machines de forage fonctionnent à assez élevé
vitesses et accueillir des exercices jusqu'à 12 mm de diamètre.
2 Machine de forage sensible
Il s'agit d'une petite machine utilisée pour percer de petits trous dans les travaux légers. Dans cette machine de forage,
la pièce à usiner est monté sur la table et de forage est introduit dans l'ouvrage de commande manuelle purement.
Haute vitesse de rotation de la perceuse et nourries à la main sont les principales caractéristiques des forages sensibles
Machine. Comme les sens l'action des opérateurs de forage dans la pièce, à tout instant, il est
appelé machine de forage sensibles. Machine de forage sensible consiste en une table horizontale,
une colonne verticale, une tête de support du moteur et le mécanisme d'entraînement, et une broche verticale.
Forets de diamètre de 1,5 à 15,5 mm peut être mis en rotation dans la broche de perçage sensible
Machine. En fonction de la fixation de la base de la machine, il peut être classé dans
les types suivants:
1. Banc de montage machine de forage, et
2. Monté au sol machine de forage
3 Machine de forage vertical
La machine de forage verticale est plus grande et plus lourd que l'une machine de forage sensibles. Il
est conçu pour manipuler des pièces de taille moyenne et est fourni avec dispositif d'alimentation de puissance.
Dans cette machine un grand nombre de vitesses de rotation et des aliments pour peut être disponible pour le forage
les différents types de travail. Machines de forage verticaux sont disponibles en différentes tailles et avec
capacités de forage divers (allant jusqu'à 75 mm de diamètre exercices). La table de la machine
a également différents types d'ajustements. Sur la base de la construction, il ya deux générale
types de machines de forage verticale:
(1) section de la colonne ronde ou à la machine de forage pilier.
(2) section de la colonne Box.
La section ronde de colonne de forage Machine verticale comprend une colonne ronde que
la machine de forage verticale a une section de colonne boîte. Les autres caractéristiques de construction de
les deux sont identiques. Machines colonne de zone de posséder plus de force de la machine et la rigidité par rapport
à ceux ayant la colonne de section ronde.
4 Perceuse radiale
 La machine de forage se compose d'un radiale
lourde, rond colonne verticale supportant un bras horizontal qui porte la tête de forage. Bras peut
être soulevé ou abaissé sur la colonne et peut également être pivoté autour d'une position quelconque sur le
travailler et peut être bloqué dans n'importe quelle position. La tête de forage contenant mécanisme de rotation et
alimenter le forage est monté sur un bras radial et peut être déplacé horizontalement sur les guidages
et serrée dans la position souhaitée. Ces ajustements de bras et la tête de forage permettent l'
opérateur de localiser le foret rapidement sur n'importe quel point sur le travail. Le tableau de perçage radial
machine peut également être tourné par 360 °. La taille maximale du trou que la machine
peut forer n'est pas plus de 50 mm. De puissants moteurs d'entraînement sont adaptés directement dans la tête
de la machine et un large éventail de sources d'alimentation sont disponibles ainsi que sensible et adaptée
manuel se nourrit. La perceuse radiale est principalement utilisé pour le forage de moyenne à grande et
pièces lourdes. Selon les différents mouvements de bras horizontal, une table et de forage
la tête, la machine de forage verticale peuvent être classés en types suivants-
1. Plaine perceuse radiale
2. Semi perceuse universelle, et
3. Perceuse universelle.

DRILLING MACHINES

DRILLING MACHINE

..1 INTRODUCTION
Drilling is an operation of making a circular hole by removing a volume of metal from
the job by cutting tool called drill. A drill is a rotary end-cutting tool with one or more cutting
lips and usually one or more flutes for the passage of chips and the admission of cutting fluid.
A drilling machine is a machine tool designed for drilling holes in metals. It is one of the most
important and versatile machine tools in a workshop. Besides drilling round holes, many
other operations can also be performed on the drilling machine such as counter- boring,
countersinking, honing, reaming, lapping, sanding etc.
2 CONSTRUCTION OF DRILLING MACHINE
In drilling machine the drill is rotated and fed along its axis of rotation in the stationary
workpiece. Different parts of a drilling machine are  discussed
below: (i) The head containing electric motor, V-pulleys and V-belt which transmit rotary
motion to the drill spindle at a number of speeds. (ii) Spindle is made up of alloy steel. It
rotates as well as moves up and down in a sleeve. A pinion engages a rack fixed onto the
sleeve to provide vertical up and down motion of the spindle and hence the drill so that the
same can be fed into the workpiece or withdrawn from it while drilling. Spindle speed or the
drill speed is changed with the help of V-belt and V-step-pulleys. Larger drilling machines are
having gear boxes for the said purpose. (iii) Drill chuck is held at the end of the drill spindle
and in turn it holds the drill bit. (iv) Adjustable work piece table is supported on the column
of the drilling machine. It can be moved both vertically and horizontally. Tables are generally
having slots so that the vise or the workpiece can be securely held on it. (v) Base table is
a heavy casting and it supports the drill press structure. The base supports the column, which
in turn, supports the table, head etc. (vi) Column is a vertical round or box section which rests
on the base and supports the head and the table. The round column may have rack teeth cut
on it so that the table can be raised or lowered depending upon the workpiece requirements.
This machine consists of following parts
1. Base
2. Pillar
3. Main drive
4. Drill spindle






3 TYPES OF DRILLING MACHINE
Drilling machines are classified on the basis of their constructional features, or the type
of work they can handle. The various types of drilling machines are:
(1) Portable drilling machine
(2) Sensitive drilling machine
(a) Bench mounting
(b) Floor mounting
(3) Upright drilling machine
(a) Round column section
(b) Box column section machine
(4) Radial drilling machine
(a) Plain
(b) Semiuniversal
(c) Universal
(5) Gang drilling machine
(6) Multiple spindle drilling machine
(7) Automatic drilling machine
(8) Deep hole drilling machine
(a) Vertical
(b) Horizontal
Few commonly used drilling machines are described as under:

1 Portable Drilling Machine
A portable drilling machine is a small compact unit and used for drilling holes in worpieces
in any position, which cannot be drilled in a standard drilling machine. It may be used for
drilling small diameter holes in large castings or weldments at that place itself where they
are lying. Portable drilling machines are fitted with small electric motors, which may be
driven by both A.C. and D.C. power supply. These drilling machines operate at fairly high
speeds and accommodate drills up to 12 mm in diameter.
2 Sensitive Drilling Machine
It is a small machine used for drilling small holes in light jobs. In this drilling machine,
the workpiece is mounted on the table and drill is fed into the work by purely hand control.
High rotating speed of the drill and hand feed are the major features of sensitive drilling
machine. As the operator senses the drilling action in the workpiece, at any instant, it is
called sensitive drilling machine. A sensitive drilling machine consists of a horizontal table,
a vertical column, a head supporting the motor and driving mechanism, and a vertical spindle.
Drills of diameter from 1.5 to 15.5 mm can be rotated in the spindle of sensitive drilling
machine. Depending on the mounting of base of the machine, it may be classified into
following types:
1. Bench mounted drilling machine, and
2. Floor mounted drilling machine
3 Upright Drilling Machine
The upright drilling machine is larger and heavier than a sensitive drilling machine. It
is designed for handling medium sized workpieces and is supplied with power feed arrangement.
In this machine a large number of spindle speeds and feeds may be available for drilling
different types of work. Upright drilling machines are available in various sizes and with
various drilling capacities (ranging up to 75 mm diameter drills). The table of the machine
also has different types of adjustments. Based on the construction, there are two general
types of upright drilling machine:
(1) Round column section or pillar drilling machine.
(2) Box column section.
The round column section upright drilling machine consists of a round column whereas
the upright drilling machine has box column section. The other constructional features of
both are same. Box column machines possess more machine strength and rigidity as compared
to those having round section column.
4 Radial Drilling Machine
 The radial drilling machine consists of a
heavy, round vertical column supporting a horizontal arm that carries the drill head. Arm can
be raised or lowered on the column and can also be swung around to any position over the
work and can be locked in any position. The drill head containing mechanism for rotating and
feeding the drill is mounted on a radial arm and can be moved horizontally on the guide-ways
and clamped at any desired position. These adjustments of arm and drilling head permit the
operator to locate the drill quickly over any point on the work. The table of radial drilling
machine may also be rotated through 360 deg. The maximum size of hole that the machine
can drill is not more than 50 mm. Powerful drive motors are geared directly into the head
of the machine and a wide range of power feeds are available as well as sensitive and geared
manual feeds. The radial drilling machine is used primarily for drilling medium to large and
heavy workpieces. Depending on the different movements of horizontal arm, table and drill
head, the upright drilling machine may be classified into following types-
1. Plain radial drilling machine
2. Semi universal drilling machine, and
3. Universal drilling machine.

Boiler

Boiler 
It's called boiler to a container used to heat water. In systems of heating , the boiler is the device that heats the water by means of a fuel , which is then distributed by the transmitters through a network of pipes .

 Description

Basically consists of a boiler house , where combustion occurs and a heat exchanger where water is heated. Also must have a system for evacuating gases from combustion.
The water can be heated to different temperatures. In normal boilers are usually not exceed 90 ° C below the boiling point of water at atmospheric pressure. In larger boilers, to serve neighborhoods, you get to 140 ° C, maintaining high pressure in the pipes so it does not boil dry (superheated water). There are also steam boiler in which water is conveyed to evaporation and the vapor is distributed to the terminal elements, but in Europe is quite out of use, because the surface temperature thereof is very high and cause danger of burns. There are also boiler in which water is heated to temperatures below 70 ° C and high performances ( condensing boiler ).
The fuel used can be solid ( wood , coal ), liquids ( fuel oil , diesel ) or gaseous ( liquid petroleum gas or LPG , natural gas ), which determines the shape of the boilers.


 boiler fluid fuels
The fuel is prepared and burned in a burner in which fuel is mixed with the precise amount of air within the home is driven by a fan, where combustion occurs. When the fuel is liquid ( oil ) is required to achieve the pulverized mixture. Gaseous fuels also be mixed with air, but need not pulverize.
There are also specific boiler fuel gases with atmospheric burner . The gas is let out through a nozzle so that, by Venturi effect , sucks air and mixes with it in proper proportion and burned in a suitable burners, divided into small flames, within a suitable heat exchanger. The best known of these boilers are called murals, but also exist in large sizes. 1
Regulating the power in the two types is made by regulating the size of the flame (modulating burners) or by stopping and starting the burner.
 solid fuel boiler
In the solid fuel, the home consists of two superimposed compartments. In the upper hearth , put the fuel on a grate. The bottom ash , receives fuel ash. On the door it enters the air required for combustion and fumes are drawn through a duct (flue or chimney) portrait, thermal draft . The heat is shooting itself in the home creates a lack of pressure sucks the combustion air. The power regulation is done by opening or closing the air inlet.
Coal is used as fuel, or now biomass.
 Accessories
They must also have accessories such as:
burners
Expansion vessel
gauges
thermometers (temperature probes)
Safety lines
safety valve
and control valves

The most common accessories are as follows:
Observing Accessories to monitoring the operation of the boiler:
level tubes
test cocks
gauges
thermometers
gas analyzers
Accessories Security, designed to avoid excessive pressure steam generation in the boiler:
lever and counterweight
Direct weight
spring
fusible plug
alarm systems
Water feed accessories:
water feed pump
water injector
Accessories supply of fuel:
burners for liquid and gaseous fuels
Mechanical burners for solid fuel
manual elements
Cleaning accessories:
records, or cleaning caps
punga valves
pungas retention Estaque
escabiadores
chimney sweeps

RAPID THERMAL PROCESSING

Rapid Thermal Processing


Rapid Thermal Processing (dt: rapid thermal processing ) is an umbrella term for the processing of wafers in a high-temperature process in which a very rapid heating of the wafer with halogen lamps is achieved.

Principle 

Integrated into the wafer processing chamber by several halogen lamps (usually 150-250 pieces at 200 mm wafers) with a total capacity of 40 kW and more heated to a temperature of 1000 ° C.
Due to the high efficiency of the lamps are heating rates (engl. ramp-up ) above 100 degrees per second. After switching off the halogen lamps of the wafer cools down again very quickly (English ramp down , about 50 degrees per second). Most RTP processes take place under vacuum to an unwanted oxidation to avoid
Processes 

Rapid thermal annealing 


Rapid thermal annealing (RTA, dt: rapid thermal annealing ) is used for healing of the crystal structure of the wafer, for example, after implantation processes . By this method, are crystal lattice defects in the wafer treated reduced and thus improves the electrical properties. To achieve this, the wafer 10-20 seconds to temperatures around 1000 ° C is brought. May balance out any minor dislocations in the crystal and dopants include at interstitial places better in the crystal lattice. By the short process times, however, the further diffusion of the dopants is limited to a minimum.
Rapid thermal oxidation
Rapid thermal oxidation (RTO, dt: rapid thermal oxidation ) is used to produce very thin oxides (<20 angstroms), primarily silicon dioxide on silicon substrates, for example, the screen oxide than for implantation processes are used. The process builds upon the thermal oxidation of silicon dar. In contrast to thermal oxidation, in which a plurality of wafers are processed simultaneously in an oxidation furnace, it is at RTO system usually to single wafer processing equipment. RTO is in terms of oxide growth is not significantly faster than the oxidation in high oxidation furnaces, considering, but the entire process (loading, high heat, oxidation, and cooling) reduces the time effort from hours to a few minutes, but only for one instead of 50 wafers.
Other applications

Production of titanium silicide by coating a titanium layer of approximately 40 nm thickness and subsequent conversion into a silicide by RTP

ANNEALING

Annealing
The annealing of a metal part or of a material is a method corresponding to a heating cycle. This is a step gradual rise in temperature followed by controlled cooling. This procedure, common in materials science, to change the physical characteristics of the metal or the material studied. This is especially used to ease the stress relaxation that can accumulate in the heart of the matter, as a result of mechanical or thermal stresses, the steps involved in synthesis and shaping materials. At the time of annealing, the grains (single crystals) of material form again and again somehow, their "steady state".
The annealing is also used to change the magnetic properties of a room.
The crystallization annealing after cold working , aims to give the metal an optimal grain size for future use (folding, stamping , ...).

Necessity of annealing: in metallurgy 

The rolling of a cold steel contributes to hardening and loss of ductility of the metal. Grain growth is necessary to find exploitable metallurgical characteristics.
Examples of use of annealing:
adaptation of the metal grain size for optimum performance (after casting)
Elimination of residual stresses (plastic deformation)
reduction in the hardness for a machining
obtaining single-crystal pieces of unique features (eg rotor blades of turbo-machinery)
...
Process 

The annealing is obtained by raising the temperature of the metal at temperatures ranging from 500  ° C to 850  ° C . The quality of annealing requires heating cycle (time of rise in temperature, holding time) under control (it can be slow or fast).
It is necessary to respect certain values ​​coupled holding time and heating temperature for complete recrystallization.
The heating rate influences the size of grains (and their number). Depending on the original structure and the desired grain size, it will be faster or slower. The holding time, the heating temperature and the rate of cooling influencing more the grain size.
The descent is more rapid (without reaching quench rates), most grains remain small.
If quenching is desired, it can be performed instead of cooling annealing.

Slow cycle and rapid cycling 

The slow cycle of annealing a steel is performed by placing the coils in the bells for 30 to 40 hours. The continuous annealing allows for him a cycle of rapid heating (90 seconds + or - 30 seconds). the cooling step should be as slow. For example, the bell-type furnaces HICO/H2 use at the end of the heating cycle that begins with a cooler air cooling, to a temperature of 300  ° C , followed by a water spray until at a temperature of 70  ° C .

Interest of continuous annealing

Appeared in the 1960s, continuous annealing brings together on a continuous line operations annealing, cold working, inspection, oiling, marking, edge trimming and winding. It allows a significant time savings compared to the annealing bells (also called annealing base).

Microelectronics 

Annealing is a technique also used in processes for microelectronics . It allows for example:
the diffusion of dopants ( boron , arsenic , phosphorus , etc..) in a semiconductor intrinsic
in the case of one or more layers of metal (s) on a semiconductor metal diffusion in the semiconductor, thereby changing its nature and thereby enhancing or changing the nature of the junction with the metal
improvement of a ohmic contact by forming silicide - or as the term used saliciure - (case of silicon )
transformation of a Schottky contact in ohmic contact (for example by annealing a layer of aluminum on a layer of silicon)
restoring a damaged surface for a semiconductor simple: when a semiconductor single (non-binary, tertiary or quaternary, etc). as silicon or germanium is damaged, for example following a burn plasma or reactive ion etching (bombarding the surface with ions and electrons), it is possible to anneal the semiconductor in an attempt to restore the surface. This technique does not work with semiconductor binary (or tertiary, etc..) Because the heat tends to disintegrate the alloy of the two (or more) elements used.