PROSESPROSES--PROSES PROSES PROSES

Cutting tools (e.g., brazing cemented carbide inserts to shanks) ... increased cross-section of the part at the joint. 13 2. Lap Joints for Brazing As...

0 downloads 15 Views 1MB Size
PROSES-PROSES PROSESPENYAMBUNGAN - 1 SME 2713 – Manufacturing Processes Assoc Prof Zainal Abidin Ahmad

Assoc Prof Zainal Abidin Ahmad

Page 1

Outline 1. 2. 3. 4. 5. 6 6.

Introduction Brazing g Soldering Welding Mechanical fasteners Adh i Adhesives

Assoc Prof Zainal Abidin Ahmad

Page 2

1

1. Introduction

Assoc Prof Zainal Abidin Ahmad

25 August 2008

Page 3

Assoc Prof Zainal Abidin Ahmad

4

2

25 August 2008

5

Assoc Prof Zainal Abidin Ahmad

1. Introduction - Joining and Assembly Distinguished ƒ

Joining - welding, brazing, soldering, and adhesive bonding. bonding • These processes form a permanent or semi-permanent joint between parts.

ƒ

Assembly - mechanical methods (usually) of fastening parts together. • Some of these methods allow for easy disassembly, disassembly while others do not.

Assoc Prof Zainal Abidin Ahmad

Page 6

3

1. Introduction - Welding Joining process in which two (or more) parts are coalesced at their contacting surfaces by application of heat and/or pressure

ƒ

• Many welding processes are accomplished by heat alone, with no pressure applied • Others by a combination of heat and pressure • Still others by pressure alone with no external heat • In I some welding ldi processes a filler fill material t i l is i added dd d to t facilitate coalescence

Assoc Prof Zainal Abidin Ahmad

Page 7

1. Introduction - Why Welding is Important ƒ

Provides a permanent joint • Welded components become a single entity

ƒ

Usually the most economical way to join parts in terms of material usage and fabrication costs • Mechanical fastening usually requires additional hardware components (e.g., screws and nuts) and geometric alterations of the parts being assembled (e.g., holes)

ƒ

Not restricted i d to a factory f environment i • Welding can be accomplished "in the field"

Assoc Prof Zainal Abidin Ahmad

Page 8

4

1. Introduction - Limitations and Drawbacks of Welding ƒ ƒ ƒ ƒ

Most welding operations are performed manually and are expensive in terms of labor cost Most welding processes utilize high energy and are inherently dangerous Welded joints do not allow for convenient disassembly W ld d joints Welded j i can have h quality li defects d f that h are difficult to detect

Assoc Prof Zainal Abidin Ahmad

Page 9

1. Introduction - Why Use Mechanical Assembly? ƒ

Ease of assembly – can be accomplished with relative ease by unskilled workers • Minimum of special tooling required • In a relatively short time

ƒ

Ease of disassembly – at least for the methods that permit disassembly • Some disassembly is required for most products to perform maintenance and repair

Assoc Prof Zainal Abidin Ahmad

Page 10

5

2. Brazing & Soldering

Assoc Prof Zainal Abidin Ahmad

Page 11

2. Overview of Brazing and Soldering ƒ ƒ

Both use filler metals to permanently join metal parts but there is no melting of base metals parts, When to use brazing or soldering instead of fusion welding: • Metals have poor weldability • Dissimilar metals are to be joined • Intense I t heat h t off welding ldi may damage d components t being joined • Geometry of joint not suitable for welding • High strength is not required

Assoc Prof Zainal Abidin Ahmad

Page 12

6

2. Brazing ƒ

ƒ

Joining process in which a filler metal is melted and distributed by capillary action between faying surfaces of metal parts being joined No melting of base metals occurs • Only the filler melts

ƒ

Filler metal Tm g greater than 450°C (840°F) but less than Tm of base metal(s) to be joined

Assoc Prof Zainal Abidin Ahmad

Page 13

2. Strength of Brazed Joint ƒ

ƒ

If joint is properly designed and brazing operation is properly performed, solidified joint will be stronger than filler metal out of which it was formed Why? • Small part clearances used in brazing • Metallurgical bonding that occurs between base and filler metals • Geometric constrictions imposed on joint by base parts

Assoc Prof Zainal Abidin Ahmad

Page 14

7

2. Brazing Compared to Welding ƒ ƒ ƒ ƒ ƒ ƒ

Any metals can be joined, including dissimilar metals Can be p performed quickly q y and consistently, y, ppermitting g high production rates Multiple joints can be brazed simultaneously Less heat and power required than FW Problems with HAZ in base metal are reduced Joint areas that are inaccessible bby man many welding elding processes can be brazed; capillary action draws molten filler metal into joint

Assoc Prof Zainal Abidin Ahmad

Page 15

2. Disadvantages and Limitations of Brazing ƒ ƒ ƒ ƒ

Joint strength is generally less than a welded joint Joint strength g is likelyy to be less than the base metals High service temperatures may weaken a brazed joint Color of brazing metal may not match color of base metal parts, a possible aesthetic disadvantage

Assoc Prof Zainal Abidin Ahmad

Page 16

8

2. Brazing Applications ƒ ƒ ƒ ƒ ƒ ƒ ƒ

Automotive (e.g., joining tubes and pipes) Electrical equipment q p (e.g., ( g , jjoiningg wires and cables)) Cutting tools (e.g., brazing cemented carbide inserts to shanks) Jewelry Chemical process industry Pl mbing and heating contractors join metal pipes and Plumbing tubes by brazing Repair and maintenance work

Assoc Prof Zainal Abidin Ahmad

Page 17

2. Brazing Applications ƒ

Spectacle frames made of stainless steel can be seen on this photo. They have been brazed using the induction method.

ƒ

Ice cream scoop. The materials to be brazed are made of stainless steel and brass. The flame brazing method or induction brazing can be used here.

Assoc Prof Zainal Abidin Ahmad

Page 18

9

2. Brazing Applications ƒ

ƒ

The photo shows medical scissors from an operating theatre. This contains t i a hard h d metal t l - stainless t i l steel t l brazed connection which can be made using the induction method. The working temperature of the brazing alloy is 770°C. Another example from the toolmaking industry (metal processing) is shown by these hard metal end-mills where hard metal has been brazed to steel by induction brazing or flame brazing, working temperature 690°C.

Assoc Prof Zainal Abidin Ahmad

Page 19

2. Brazing Applications ƒ

ƒ

The photos show an example of an application in the area of refrigeration and air conditioning technology. The materials to be brazed are made of copper, brass and steel. Flame brazing or ind ction bra induction brazing ing can be used sed as the brazing method. Ref : www.BrazeTec.com

Assoc Prof Zainal Abidin Ahmad

Page 20

10

2. Brazing Applications ƒ

ƒ

ƒ

ƒ

The photos show a hot water boiler in a central heating system. The through-pipes were brazed b d tto the th boiler b il using i the th flame fl brazing method The brazing alloy BrazeTec S 2 or BrazeTec S 94 with respective working temperatures of 740 and 760°C can be used as alloys. N fl No flux is i required i d with i h these h alloys ll due d to the fact that the brazing involves a copper to copper connection. Ref : www.BrazeTec.com

Assoc Prof Zainal Abidin Ahmad

Page 21

2. Brazing Applications ƒ ƒ

ƒ

A stainless steel pot is shown here, onto which a spout has been brazed via flame brazing. We recommend for this zinc-free BrazeTec 6009 brazing alloy (working temperature ca. 720°C) and BrazeTec special h flux. Ref : www.BrazeTec.com

Assoc Prof Zainal Abidin Ahmad

Page 22

11

2. Brazed Joints ƒ

Butt and lap joints common • Geometry of butt joints is usually adapted for brazing • Lap joints are more widely used, since they provide larger interface area between parts

ƒ

Filler metal in a brazed lap joint is bonded to base parts throughout entire interface area, rather than only at edges

Assoc Prof Zainal Abidin Ahmad

Page 23

2. Butt Joints for Brazing

(a) Conventional butt joint, and adaptations of the butt joint for brazing: (b) scarf joint, (c) stepped butt joint, (d) increased cross-section of the part at the joint.

Assoc Prof Zainal Abidin Ahmad

Page 24

12

2. Lap Joints for Brazing

(a) Conventional lap joint, and adaptations of the lap joint for brazing: (b) cylindrical parts, (c) sandwiched parts, and (d) use of sleeve to convert butt joint into lap joint. Assoc Prof Zainal Abidin Ahmad

Page 25

2. Joint Designs Used in Brazing

Joint designs commonly used in brazing operations. The clearance between the two parts being brazed is an important factor in joint strength. If the clearance is too small, the molten braze metal will not fully penetrate the interface. If it is too large, there will be insufficient capillary action for the molten metal to fill the interface. Assoc Prof Zainal Abidin Ahmad

Page 26

13

2. Brazing Design

Examples of good and poor design for brazing.

Assoc Prof Zainal Abidin Ahmad

Page 27

2. Some Filler Metals for Brazing Base metal(s) Aluminum Nickel-copper alloy Copper Steel, cast iron Stainless steel

Assoc Prof Zainal Abidin Ahmad

Filler metal(s) Aluminum and silicon Copper Copper and phosphorous Copper and zinc Gold and silver

Page 28

14

2. Desirable Brazing Metal Characteristics ƒ ƒ ƒ ƒ ƒ

Melting temperature of filler metal is compatible with base metal Low surface tension in liquid phase for good wettability High fluidity for penetration into interface Capable of being brazed into a joint of adequate strength g for application pp Avoid chemical and physical interactions with base metal (e.g., galvanic reaction)

Assoc Prof Zainal Abidin Ahmad

Page 29

2. Applying Filler Metal

Several techniques for applying filler metal in brazing: (a) torch and filler rod. Sequence: (1) before, and (2) after.

Assoc Prof Zainal Abidin Ahmad

Page 30

15

2. Brazing Fluxes ƒ

ƒ

Similar purpose as in welding; they dissolve, combine with, and otherwise inhibit formation of oxides and other unwanted byproducts in brazing process Characteristics of a good flux include: • • • •

Low melting temperature Low viscosity so it can be displaced by filler metal Facilitates wetting Protects joint until solidification of filler metal

Assoc Prof Zainal Abidin Ahmad

Page 31

2. Heating Methods in Brazing ƒ ƒ ƒ ƒ ƒ ƒ

Torch Brazing - torch directs flame against work in vicinity of joint Furnace Brazing - furnace supplies heat Induction Brazing – heating by electrical resistance to high-frequency current in work Resistance Brazing - heating by electrical resistance in parts p Dip Brazing - molten salt or molten metal bath Infrared Brazing - uses high-intensity infrared lamp

Assoc Prof Zainal Abidin Ahmad

Page 32

16

2. Furnace brazing

S Several l techniques h i for f applying l i filler fill metall in i brazing: b i (b) ring of filler metal at entrance of gap. Sequence: (1) before, and (2) after.

Assoc Prof Zainal Abidin Ahmad

Page 33

2. Induction heating ƒ

What is Induction Heating?

Assoc Prof Zainal Abidin Ahmad

Page 34

17

2. Brazing methods ƒ ƒ

ƒ

ƒ

Brazing could be performed manually with a hand-held torch, or automatically in a furnace. The joints should be properly cleaned before brazing and all methods, except vacuum brazing and vibration brazing, require flux. The use of flux causes environmental problems and the remaining flux must be completely removed to eliminate corrosion. Accordingly, vacuum brazing is more and more used, for example, in the production of automotive heat exchangers

Assoc Prof Zainal Abidin Ahmad

Page 35

2. Brazing methods ƒ

Torch brazing machine

Assoc Prof Zainal Abidin Ahmad

Page 36

18

2. Brazing methods ƒ

Induction brazing

Assoc Prof Zainal Abidin Ahmad

Page 37

2. Brazing methods ƒ

Induction brazing

Assoc Prof Zainal Abidin Ahmad

Page 38

19

2. Brazing methods ƒ ƒ

ƒ ƒ ƒ

The bridge of a sunglass frame is brazed. Various metal frame parts are joined during the induction brazing process. Handy & Harman/Lucas-Milhaupt filler metal in wire from is used. Brazing provides invisible joints as this browbar is brazed. A total of 10 joints are formed during the fully automated process.

Assoc Prof Zainal Abidin Ahmad

Page 39

2. Brazing methods ƒ

ƒ

Another application example from air conditioning technology is a condenser for an air conditioning unit. i A detailed photo of the copper pipe bend is shown. For brazing this connection, the flame brazing method can be used or alternatively, depending on the working material, the furnace brazing method with an inert gas. For copper to copper b i the brazing, th phosphorus-containing h h t i i BrazeTec S 2 brazing alloys with a working temperature of ca. 740°C and BrazeTec S 94 with a working temperature of ca. 760°C can be used.

Assoc Prof Zainal Abidin Ahmad

Page 40

20

3. Soldering

Assoc Prof Zainal Abidin Ahmad

Page 41

3. Soldering ƒ

ƒ ƒ ƒ ƒ

Joining process in which a filler metal with Tm less than or equal q to 450C ((840F)) is melted and distributed by capillary action between faying surfaces of metal parts being joined No melting of base metals, but filler metal wets and combines with base metal to form metallurgical bond Soldering similar to brazing, and many of the same heating methods are used Filler metal called solder Most closely associated with electrical and electronics assembly (wire soldering)

Assoc Prof Zainal Abidin Ahmad

Page 42

21

3. Soldering Advantages / Disadvantages Advantages: ƒ Lower energy gy than brazing g or fusion welding g ƒ Variety of heating methods available ƒ Good electrical and thermal conductivity in joint ƒ Easy repair and rework Disadvantages: ƒ Low joint strength unless reinforced by mechanically means ƒ Possible weakening or melting of joint in elevated temperature service Assoc Prof Zainal Abidin Ahmad

Page 43

3. Solders ƒ ƒ ƒ

ƒ ƒ

Usually alloys of tin (Sn) and lead (Pb). Both metals have low Tm Lead is poisonous and its percentage is minimized in most solders Tin is chemically active at soldering temperatures and promotes wetting action for successful joining I soldering In ld i copper, copper andd tin i form f intermetallic compounds that strengthen bond Silver and antimony also used in soldering alloys

Assoc Prof Zainal Abidin Ahmad

Page 44

22

3. Mechanical Means to Secure Joint

Techniques for securing the joint by mechanical means prior to soldering in electrical connections: (a) crimped lead wire on PC board; (b) plated through-hole on PC board to maximize solder contact surface; (c) hooked wire on flat terminal; and (d) twisted wires. Assoc Prof Zainal Abidin Ahmad

Page 45

3. Functions of Soldering Fluxes ƒ ƒ ƒ ƒ ƒ ƒ

Be molten at soldering temperatures Remove oxide films and tarnish from base part p surfaces Prevent oxidation during heating Promote wetting of faying surfaces Be readily displaced by molten solder during process Lea e residue Leave resid e that is non-corrosive non corrosi e and nonconductive noncond cti e

Assoc Prof Zainal Abidin Ahmad

Page 46

23

3. Soldering Methods ƒ ƒ

Many soldering methods same as for brazing, except less heat and lower temperatures are required Additional methods: • Hand soldering – manually operated soldering gun • Wave soldering – soldering of multiple lead wires in printed circuit cards • Reflow soldering –used for surface mount components on printed circuit cards

Assoc Prof Zainal Abidin Ahmad

Page 47

3. Soldering Methods ƒ

Soldering with a soldering iron.

Assoc Prof Zainal Abidin Ahmad

Page 48

24

3 Joint 3. Designs Used in Soldering

Joint designs commonly used for soldering. Note that examples (e), (g), (i), and (j) are mechanically joined prior to being soldered, for improved strength. Source: American Welding Society. Assoc Prof Zainal Abidin Ahmad

Page 49

3. Soldering Methods

Wave soldering, in which molten solder is delivered up through a narrow slot onto the underside of a printed circuit board to connect the component lead wires. Assoc Prof Zainal Abidin Ahmad

Page 50

25

3. Soldering Methods ƒ

Convection reflow soldering. This method consists in soldering the component by heating air or N2 gas with a heater and spraying compressed gas from a nozzle onto the joint. The temperature is adjusted by adjusting the heat source or the flow of gas

Assoc Prof Zainal Abidin Ahmad

Page 51

3. Soldering Methods ƒ

Convection reflow soldering

Assoc Prof Zainal Abidin Ahmad

Page 52

26

3. Soldering Methods ƒ

Convection infra-red reflow soldering. This method solves the problem of the comparatively longer soldering time of the C Convection ti reflow fl method th d by b combining bi i it with ith infrared i f d reflow fl

Assoc Prof Zainal Abidin Ahmad

Page 53

3. Soldering IC interconnects :

Assoc Prof Zainal Abidin Ahmad

Page 54

27