Electro-Magnetic and High Velocity Forming

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Questions and Answers

What is the primary purpose of adding lubricants to powders during the compaction process?

To decrease the porosity of the compact

To enhance the bonding of the compact

To reduce the production rate

To reduce die wall friction and increase flowability (correct)

Which of the following statements correctly describes the difference between mixing and blending?

Mixing is only done dry; blending is always done wet.

Mixing involves thorough intermixing of powders; blending focuses on grain size differences. (correct)

Mixing is for powders of the same composition; blending is for different compositions.

Mixing leads to lower density; blending leads to higher density.

What is the range of compacting pressure typically used for metal powders?

320 to 800 MPa for all powders

80 to 1600 MPa (correct)

40 to 160 MPa

200 to 400 MPa

What primarily contributes to the green strength of the compact during the compacting process?

Sliding combined with pressure and mechanical interlocking Signup and view all the answers

For which type of metal powders is the highest compacting pressure of 400 to 700 MPa typically required?

Iron, steel, and Ni alloys Signup and view all the answers

What is the primary use of the melt atomization method?

Making pre-alloyed powders Signup and view all the answers

Which process employs an electric arc between electrodes in an inert gas environment?

Melt atomization Signup and view all the answers

What is the result of the reduction process described?

Production of pure metals from their oxides Signup and view all the answers

What shape do the particles produced by the reduction method typically have?

Irregular and porous Signup and view all the answers

Which method is primarily used for producing coarse powder particles?

Machining Signup and view all the answers

What equipment is commonly used in the crushing process for brittle metals?

Rotary mills Signup and view all the answers

In the soluble gas process, how is molten metal transformed into small particles?

By pressure flow into a vacuum Signup and view all the answers

What materials can be produced using the melt atomization method?

Stainless steel and cobalt-base alloys Signup and view all the answers

Which reduction reaction involves iron (Fe) and carbon monoxide (CO)?

Fe3O4 + 4CO → 3Fe + 4CO2 Signup and view all the answers

What term describes the amount of powder needed to completely fill the die or container cavity before compacting?

Fill or Powder fill Signup and view all the answers

How is the fill calculated?

Median height of compact desired multiplied by Compression Ratio Signup and view all the answers

What does flow rate measure in the context of powder processing?

The time for a measured quantity of powder to flow through an orifice Signup and view all the answers

Which particle shape is noted for its excellent sintering properties?

Spheroidal particles Signup and view all the answers

Why is it important for particle size to be controlled in powder processing?

To avoid large surface area-to-volume ratios Signup and view all the answers

What effect does the addition of stearate have on powder flowability?

Increases flowability Signup and view all the answers

Which type of particle shape is superior for achieving good green strength in parts?

Irregularly shaped Signup and view all the answers

What happens if particles are too large in powder metallurgy applications?

They may not produce the required structure for the process Signup and view all the answers

What defines the flowability of a powder?

The shape and size distribution of the powder particles Signup and view all the answers

Which of the following contributes to the agglomeration of fine particles in powder processing?

Large surface area-to-volume ratio Signup and view all the answers

Which metal powders are noted for presenting explosion and fire hazards in a finely divided state?

Aluminum, Magnesium, Zicronium, Titanium Signup and view all the answers

What is the typical size of a compact on a 900 kN capacity press?

100 mm diameter and 150 mm long Signup and view all the answers

What problem is associated with the residual porosity of sintered compacts?

It makes them rougher than the compacting die Signup and view all the answers

What is a major thermal difficulty experienced during the sintering operation of low melting point metals?

Oxide formation during the process Signup and view all the answers

What is necessary for the atmosphere in the furnace during the sintering process?

Reducing Signup and view all the answers

What method is described as breaking molten metal into droplets using a stream?

Atomization Signup and view all the answers

Which of the following metals cannot have its oxides reduced at temperatures below the metal's melting point?

Tin Signup and view all the answers

What effect does heating to about 350°C have on the metal powder that restores ductility?

It dissociates the powder into pure metal and hydrogen. Signup and view all the answers

Which process is used to obtain pure metals like Iron and Nickel from carbonyls?

Thermal decomposition Signup and view all the answers

What characteristic of metal powders indicates the area available for bonding?

Surface area Signup and view all the answers

Which of the following defines theoretical density in powder metallurgy?

Mass per unit volume of a non-porous metal. Signup and view all the answers

How is density measured in relation to powder metallurgy components?

It is determined indirectly through calculations. Signup and view all the answers

At what temperature does the decomposition of carbonyls to obtain pure metals occur?

High temperatures above 600°C Signup and view all the answers

What happens to the metal powder particles obtained through thermal decomposition?

They are almost spherical in shape. Signup and view all the answers

Which metal is not commonly produced using thermal decomposition of carbonyls?

Copper Signup and view all the answers

What is the significance of theoretical density in powder metallurgy?

It is the highest possible density for comparative purposes. Signup and view all the answers

Which carbonyl reaction is correctly paired with the metal it produces?

Ni + 4CO → Ni(CO)4 Signup and view all the answers

What is a characteristic of electro-magnetic forming?

It has low operating costs and is suitable for automation. Signup and view all the answers

Which of the following statements accurately differentiates between conventional and high-speed billet forming machines?

High-speed machines produce energy solely from shock waves, while conventional machines do not. Signup and view all the answers

Which factor is not a limitation of the electro-magnetic forming process?

High operational complexity. Signup and view all the answers

In the context of conventional machines, which speed range reflects hydraulic presses?

Up to 1.5 m/s Signup and view all the answers

What defines the primary energy source for deformation in high-speed sheet metal forming machines?

Shock waves from an external source Signup and view all the answers

Which of the following best describes the force and kinetic energy relationship in a drop hammer?

Zero force, large kinetic energy Signup and view all the answers

How does the impact speed of high-speed billet forming machines compare to traditional forming methods?

It is much higher than most conventional machines. Signup and view all the answers

What is the primary consequence when the induced stress in the work material exceeds its ultimate shear stress?

Rupture of the material occurs. Signup and view all the answers

What role does the accumulator play in the water jet machining process?

It eliminates pulsation and acts as an energy reservoir. Signup and view all the answers

Which materials are typically used for the nozzle in water jet machining?

Sintered diamond, sapphire, or Tungsten Carbide Signup and view all the answers

What is a noted advantage of using water as the energy transfer medium in water jet machining?

Water is cheap, non-toxic, and easy to dispose of. Signup and view all the answers

What is the typical exit diameter range for the nozzle used in water jet machining?

0.05 to 0.35 mm Signup and view all the answers

Which of the following is NOT an advantage of water jet machining?

High operating and maintenance costs. Signup and view all the answers

In the context of water jet machining, what is the primary purpose of the nozzle?

To concentrate and direct high-pressure water for cutting. Signup and view all the answers

What range of water pressures are typically used in water jet machining systems?

1500 to 4000 N/mm2 Signup and view all the answers

How does the high velocity jet of water primarily affect the workpiece during machining?

It converts kinetic energy into pressure energy, inducing high stresses. Signup and view all the answers

What is the primary mechanism by which finer particles are obtained in impact milling?

Particles are hurled against a stationary surface. Signup and view all the answers

Which method uses hydrogen gas for the production of powder from titanium alloys?

Condensation Signup and view all the answers

In the electrolytic deposition process for producing iron, what serves as the cathode?

Sheets of stainless steel Signup and view all the answers

Which milling technique involves particles being entrained in two opposing fluid streams?

Fluid energy milling Signup and view all the answers

What structure is typically formed during the electrolytic deposition of iron?

Soft spongy dendritic structure Signup and view all the answers

What is a notable advantage of using Abrasive Jet Machining (AJM)?

Low capital cost Signup and view all the answers

What is a common disadvantage of Abrasive Jet Machining (AJM)?

Risk of stray cutting Signup and view all the answers

In which application is Abrasive Jet Machining (AJM) NOT commonly used?

Electroplating Signup and view all the answers

Which of the following materials is NOT typically machined using Water Jet Machining (WJM)?

Metals Signup and view all the answers

What kind of dimensional tolerance can be achieved using Abrasive Jet Machining (AJM)?

± 0.05 mm Signup and view all the answers

What is the function of the pressure regulator in the AJM system?

To regulate gas flow and pressure Signup and view all the answers

Which mechanism is used to control the movement of the nozzle in AJM?

Cam or pantograph mechanism Signup and view all the answers

What is the typical power input for Abrasive Jet Machining (AJM)?

0.25 kW Signup and view all the answers

What type of materials are primarily cut using high-pressure water jets in Water Jet Machining (WJM)?

Wood and textiles Signup and view all the answers

What is the primary shape of powder particles generated through the atomization process?

Spherical or pear shaped Signup and view all the answers

Which parameter is NOT typically controlled in the atomization process to influence particle shape and size?

Cooling rate of the powder Signup and view all the answers

What type of metals are primarily produced using atomization due to their low melting point?

Low melting point metals like aluminum and zinc Signup and view all the answers

What type of equipment is typically used to collect the powder generated from the atomization process?

Standard dust collector system Signup and view all the answers

How does the pressure of the gas stream affect the atomization process?

It influences the shape and size of the powder particles. Signup and view all the answers

In which scenario is the atomization process particularly problematic?

When corrosion action on the nozzle occurs. Signup and view all the answers

Which method is NOT involved in producing metal powders mentioned in the content?

Centrifugation Signup and view all the answers

What is the outcome of controlling the process parameters during powder production?

Varied particle shapes and sizes. Signup and view all the answers

What happens to the molten metal as it is transformed into powder during the atomization process?

It is broken into droplets. Signup and view all the answers

Which of the following describes an important factor in the selection of metals for the atomization process?

The melting point and resultant corrosion action. Signup and view all the answers

Study Notes

Electro-Magnetic Forming

Only relatively small components can be made via this method
Electro-magnetic forming is based on changing magnetic fields.
When a current flows in a conductor, a magnetic field forms around it
If the current changes, a current is induced in another nearby conductor.
This induced current creates a magnetic field that opposes the original field.
Repelling forces between the two conductors can be high (350 N/mm² for microseconds).
The work-piece is the second conductor and is forced against a die.
Suitable for bulging, shrinking, flaring, and swaging of tubes
The work-piece needs to be a conductor, but not necessarily magnetic
The process is limited to thin sheet metal because high pressures aren't generated.
Die materials should be low electrical conductivity, often steel or epoxy resin.
Air is evacuated from the die to prevent distortion.

High Velocity Forming

Used for sheet metal forming or billet forming
Conventional sheet metal forming machines are primarily crank and hydraulic presses.
High-speed machines have no moving parts.
Energy comes from a shock wave from a source.
Conventional billet forming machines include hydraulic, crank and eccentric presses, screw presses, drop hammers, and power hammers.
High-speed machines operate at higher speeds (6 to 24 m/s or 30 to 300 m/s).
The speed of the ram varies with the type of machine.

Dynapak

The Dynapak machine uses high-pressure gas to drive a piston, ram, and die
It is useful for forging, powder compacting, and sheet metal working.
High pressure gas is released, driving the piston/ram, and high force is generated.
Hydraulic jacks are used to return the piston.

Petro-Forge Forming

The stored chemical energy of hydrocarbon (like petrol or diesel) moves the dies at high velocity.
It works like an internal combustion engine.

Other Unconventional Manufacturing Methods

Abrasive Jet Machining (AJM): Uses high-velocity abrasive particles to erode material.
Water Jet Machining (WJM): Uses high-velocity water jets (without abrasives) for material removal.
Ion Beam Machining (IBM): Uses ion beams for material removal.
Electric Discharge Machining (EDM), Electro-Chemical Machining (ECM), Electrical discharge grinding (EDG), Electrochemical grinding (ECG), Chemical Milling (CHM), Ultrasonic Machining (USM): These methods all use electrical discharges, chemicals or ultrasonic energy to cut/shape materials.

Powder Metallurgy

Powder metallurgy (P/M) is a manufacturing process for making components from metal powders.
It involves several steps: powder preparation, mixing, compacting, and sintering.
P/M has several advantages: cost-effectiveness and tolerance control, manufacturing high-quality, complex, and high-strength components with close tolerance.
P/M has some limitations: expensive dies and equipment are required, and the process is suitable mainly for mass production, some materials can be difficult to store, and complete density is difficult to achieve.

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Description

This quiz covers the principles and applications of electro-magnetic forming and high velocity forming techniques. Understand the mechanics behind how changing magnetic fields influence metal forming processes, as well as the advantages of using high-speed machines in manufacturing. Test your knowledge on these advanced forming methods.