Dip Brazing

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DIP BRAZING

Dip Brazing is a process of joining of Aluminum alloy parts by means of

flowing a filler metal between the joint interfaces at a temperature below the

melting point of the base metal. Upon cooling to the solid state it forms a

strong metallic bond throughout the joined area. This process is different from

other joining process e.g. welding, brazing, soldering in following aspect:

a) No distortion

b) Close dimensional accuracy

c) More than scores of joints can be dip brazed in one dip

d) Quick, Leak-proof

Consequently the application has been use in those areas:

y Where the job is intricate and conventional manufacturing process is

either very costly or takes a longer cycle time.

y No distortion is allowed in the parent item after joining process.

y Leak proofing at joints

y Joining of thin sheet to a thicker one.

The wave guides, with all the bends and twists, for RF plumbing of anycommunication Equipment, are the ideal items for dip brazing.

Parts to Be Dip Brazed Are

Cleaned of oil, grease and freed of excess oxide,

Assembled and jigged along with the necessary filler metal (dry flux).

Heated to approximately 580 deg Celsius for about 45 minutes

Immersed in molten flux at 605 deg Celsius for about 2-3 minutes.

Removed from the molten flux, cooled and cleaned,

The assembly is now ready for use for further treatment.

One joint or a hundred can be formed during the few minutes the assembly is

submerged in the molten salt.



It is a welding method, which involves welding of material via an unknown salt

or aluminum power exported from U.S.A.

The various stages involved are:

1) Cleaning of raw material: - It involves the surface cleaning of the

material part to be joined.

2) Setting of raw material: - the different parts to be joined of various

types can be set by tag welding or by tightening by wires.

3) Cleaning

Descaling It can be done by treating it with HNo3 + HF in the

ratio of 6:4 (Removal of scales).

Degreasing this can be done by treating it with Tetra-chloro

ethylene (TCE).

4) Reassemble: - Guiding them reassembles the material parts.

5) Application of Filler material: - This filler material of aluminum powder

of same compound is applied on the place where it is to be welded.

6) Pre-heating: - the material is heated to a temperature of 580oc so that it

may come to plastic state. The time period depending upon the job.

Then due to capillary action, it sweeps into the joints.

7) Dipping in Salt water: - It is put in salt bath, which is at a temperature

of 605o c. It is done so that it gets hardened and also external powder

is washed away.

8) Air-cooling: - The job is then air-cooled.

9) Hot water cooled: - It is done in order that the stresses may not

develop if sudden cold water is applied.

10) Further cleaning is done



ADVANTAGES OF DIP BRAZING

LESS DISTORTION:

Large and extremely complex shapes can be brazed with minimal distortion atrelatively lower than welding temperatures. Dip Brazing utilizes uniform

application of heat both in the pre-heating furnace & in molten salt bath and

works in conjunction with high thermal conductivity properties associated with

Aluminum. This uniform application of heat reduces the incidence of

distortion.

REDUCED TOOLING COST:

The dip brazing process uses little if any specialized tooling. Fixturing is

generally accomplished with common fixtures that allow for quick and

inexpensive configuration changes.

MATERI AL S AV INGS:

Unlike castings or machined parts, dip brazing can be done at near final

dimension.

I MP RO V ED STRUCTUR AL INTEGRIT:

Dip brazing offers a continuous leak-proof and EMI shielded joint even with a

variety of material thicknesses.

BETTER CONDUCTI V ITY:

As the dip brazed joint is made up of aluminum, conductivity is clearly better

than that achieved with an adhesive bonded or mechanically attached

assembly.

LOWER COST:

The dip brazed process yields the lowest cost given the superior

characteristics achieved.



DESIGN FREEDO M :

The design engineer will enjoy a greater range of options using the dip

brazed process.

Reduced Tooling Costs

Reduced Design Change cost and implementation time

F ATIGUE AND THER MAL P RO P ERTIES:

The natural shape of the meniscus formed by the filler material is ideally

shaped to resist fatigue. Any stress of the assembly is evenly distributed

around the fillet and disperses the stress uniformly over a large stress area.



FABRICATION SHOP

Fabrication Shop is one of the mechanical workshops in the company. There

are several kinds of machine used for different kind of operation.For sheetmetal work first of all the work is done on sheering machine. Shearing

machine cuts the sheet. It firstly bends the sheet & then breaks the sheet by

application of heavy force through a ram.

After cutting the sheet the work piece is sent to punching machine. In this

machine punch can make holes of any shape. This punching machine is a

CNC machine, which has twenty-tool station. The program is feed into the

machine manually, by floppy or by compact disc. After punching, job is sent

forward for other operations. After punching if there is any bending work in

that job then it is sent to bending machine where bending work is done.

In circular saw the waste material is cut of the original piece. Now after

performing such operation the level of the sheet get wreck so before

performing more operations. It is sent to leveling machine in which there are

rollers, which are moving in opposite directions. The sheet is inserted in the

machine and machine levels the surface.

In Fabrication Shop there are various kinds of machine but mainly the work is

done on some machine and they are:

1. Shearing Machine (PC-1).

2. CNC-LVD Punching Machine.

3. NPB- Bending Machine.

4. 120 T- Bending Machine

5. Leveling Machine.

6. Tapping Machine.

7. Circular Saw.

8. Radial Drilling Machine.



The brief description and working of the machine is given below:

1. Shearing M achine ( P C-1):-

Shearing Machine is one of the most important machines of the fabrication

shop, because the work starts from this machine as it cuts the sheet. This

machine works on hydraulic pressure. The ram is fixed and it slides

horizontally and cut the sheet. Actually this machine do not cut, it bends the

sheet and then breaks by the action of ram. As the sheet bends and the work

done in great accuracy so clearance must be taken in account before cutting

the sheet .The clearance is the 3% of the thickness of the sheet. For holding

the sheet firmly, when we press the button first the hammer press the and

then the ram perform its work. For the long life of the cutter the ram do not act

from both side, instead of that it starts cutting from one side just like scissor.

Specification:-

Maximum sheet thickness

Aluminum - 0.5 - 6 mm

Mild steel - 0.5 - 4 mm

Stainless steel - 0.5 - 3mm

Maximum length of the sheet - 3mm

Number of strokes per minute - 18-28

Distance of frame cutting slide - 30HP

Voltage of motor - 415V

Approximate weigh - 7 tones

2. CNC-LV D Pu nching M achine: -

This machine is a CNC turret machine in which there are 20 ± tool stations in

a turret, which acts as there programming. In this machine there are four



ways to feed the program, first way is simple manual programming, second

by magnetic tape/reel, third way is by floppy and fourth by compact disc.

Programming is based on trigonometry. X & Y indicates the desired length &

width of the sheet.

Working of the machine is simple the data is fed into machine by any one of

the method & the sheet is inserted in the machine. The machine automatically

works and finally completes the job. For holding the job firmly there are two

vices, which are movable and which moves the sheet. Their jaws are

operated by oil compression.

Specification: -

Company - LVD BelgiumModel - Delta 1000 thick turret 3 indexesCNC control - Fanuc 180iElectric consumption - 23.4 KWMaximum punch tonnage - 200 KWWorking Area - 1275 mmMaximum sheet thickness - 6 mmMaximum punch dia - 88.9 mmMaximum work piece weight - 80 Kg

Position Accuracy - 0.1 mm Average repeatability - 0.05 mmNumber of tool stations - 20

7A type (up to 12.7 mm)7B type (dia 12.7 to 31.7 mm)2C type (dia 31.7 to 50.9 mm)4D type (dia up to 88.9 mm)

No. Of index station - 3(D type)Inhibited clamp zone - 220 mm (X direction)

80 mm (Y direction)Maximum speed - 75 mm/min for X & Y direction

106 mm/min for X & Y movementNibbling - 400 mm/min (+/- 5 %)

for X= 1mm And y=0 (without sheet)

Punching - 200 mm/min (+/- 5 %)for X = 25 mm

And Y = 0 (without sheet)Noise level - 90 to 100 dB



3. N P B Bending M achine:-

In this machine the tool is fixed between the jaws and the die is selected as

per our need. It is also an automatic machine. It¶s an air compressor operated

machine in which applying air pressure does the work.

The die is selected and fitted at the die holder. The job, which is to bend, is

placed on the die, which is fixed on the bed. The most important feature of

this machine is that in this machine the ram do not move, instead bed move

upward and downward and the bending work is done.

This is a kind of automatic machine; so the power of stroke, length of stroke

and the dimension of the job is numerically control where the angel of

bending is dependent on the die.

4. 120T Bending M achine:-

This is simple kind of press, working on hydraulic principle. Its tonnage is 120

tones and is completely manual operated machine. It has two hydraulic

cylinders, which are attached with the hydraulic pistons. There is oil tank

behind the machine, which is filled with oil and is used as a fluid for hydraulic

piston.

As this is a manually operated machine, so the stroke length, the die and

bending angle all are set manually. The bending angle is set by die and

stroke length is set up by scale, which is situated on the machine. To hold the

job firmly there is also clamp, which holds the job. In this machine the bed is

stationary and the ram moves upward and downward.



5. Tapping M achine:-

Tapping machine in its simplest kind consists of AC motor in which the

spindle is fitted from which a belt is fitted from motor spindle to chuck spindle

on the both spindle. There are some steps for the belt, by means of that the

speed of machine is controlled.

An important feature of this machine is that the chuck of this machine can be

rotated clockwise when the moving chuck is pressed upward. By using this

machine we can tap from 2 mm to 10 mm.

6. Leveling M achine:-

Leveling Machine is used only for leveling the surface of sheets, when the

surface of the sheet gets wrecked after performing the operation such as

cutting, punching etc.

In this machine there are rollers, which are fitted, parallel and moving in

opposite direction, when sheet is inserted in machine the rollers press the

sheet by which the sheet gets leveled.

In this machine the thickness of the sheet must be pre entered and the sheet

of roller must also be set.

7. FS Circ u lar Saw:-

Circular saw, as the name indicates is a saw, which is circular in shape. It has

two types of cutting saw used as per need. Both cutters cannot be fitted on

the machine simultaneously. The blade is ejected and changed when we

need.



The cutters used in the machine are of two types:

y Diamond edge cutters

Diamond edge cutter is a simple cutter, in which small particles of

diamond are fixed on the edge of the cutter. This type of cutter is used

to cut acrylic or non-metal sheets varying thickness from 0.5 mm to

5 mm. The most important feature of this machine is that it is used only

for cutting non-metals.

y Metal edge cutters

This is a type of cutter in which the blades are made up of metal

such as high carbon steel (HCS), high-speed steel (HSS) and other

kinds of hard metals. This cutter is used to cut the sheets of varying

thickness of 5 mm to 50 mm, and it also cuts non-metals.

8. Radial drilling machine:-

Radial drilling machine in its simplest kind consists of motor, which is

attached with drill chuck, and the chuck is hanging on the shaft, which is

attached with drill chuck, and the chuck is hanging on the shaft, which can

move in the angles. This machine can drill up to 29 mm diameter.

This machine is called Radial drilling machine because it can move 360

degree. To set it in any position there is a magnetic lock which the shaft and

do not allow it to move.

Dip Brazing

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