Advanced Metal Forming

8/8/2019 Advanced Metal Forming

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Suranaree University of Technology Jan-Mar 2007

Advanced metal formingAdvanced metal formingprocessesprocesses

Introduction/Objectives

Superplastic forming

Pressing and sintering

Isostatic pressing

Subjects of interest

Chapter 8

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This chapter aims to provide additional information on

several techniques of metal forming processes other than

those conventional process already mentioned in previous

chapters.

The requirements for the process selection will be added,

which are based on advantages and disadvantages of each

type of non-conventional metal forming processes.

ObjectivesObjectives

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Advanced techniques for metal forming are listed below;

IntroductionIntroduction

1) Superplastic forming

2) Pressing and sintering

3) Isostatic pressing (hot and cold)

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SuperplasticSuperplastic formingforming The term superplasticityis used to

describe materials that can be formed to

high strains without the formation ofunstable tensile necks.

Require controlled conditions of

appropriate temperature and strain

rate, by using low force. Produce complex shapes (3D) with

essentially constant section thickness.

Good surface finishes.

Poor creep due to small grain size.

Machines and dies are costly.Superplastic forming

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Female forming Female drape forming

Graphite coated blankput

into heated hydraulic press.

Air pressure forces sheet

into close contact with mould.


Graphite-coated blank clampedovertraycontaining heated

male mould.

Air pressure forces metal into

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Plug-assisted snap back male forming

Graphite-coated blankputinto heated press.

Blank formed into a bubble.

Male mould pressed into

bubble.

Air pressure forces metal

into close contact with mould.

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Pressing and sinteringPressing and sintering Powderis pressed in closed dies to form a green compact

which is then sintered at elevated temperature.

Produce 3D solid shapes for mainly metals and ceramics.

Near net shape process 100% material utilization. Automated machinery and dies are relatively costly.

Sintering Operation

Sequence of operations for production of cylindrical bearing

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Sintering of a powder compact

Sinteringis the "welding" together of separatepowder particles into a single solid material,

Takes place below the melting point of the

material, but at a temperature sufficiently high to

allow an acceptable rate of diffusion to occur.

Sintered products

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IsostaticIsostatic

pressingpressing

Powder is placed within a deformable container

and subjected to hydrostatic pressure.

Produce 3D bulk solid shapes for metals and

ceramics.

Allows simultaneous densification of metal

powder products have relatively low porosity.

Distortion is possible in high aspect ratiocomponents

Near net shape process100% material

utilization.

High operating cost.

Hot isostatic pressing (HIP).

process

HIP products

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Hot Isostatic Pressing (HIP)

Components are loaded

into furnace, which is placedinto pressure vessel.

Temperature and pressure

are raise simultaneously and

held. Coolingis carried out as

the gas is released (clean

and recycled) and the furnace

is removed from the pressurevessel.

Components are removed

from the furnace.

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Cold Isostatic Pressing (CIP)

Powderis sealed in a flexible

mould (or bag), of for example

polyurethane and then subjected to

a uniform hydrostatic pressure.

CIP graphite blocks

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Edwards, L. and Endean, M., Manufacturing with materials,

1990, Butterworth Heinemann, ISBN 0-7506-2754-9.

www.designinsite.dk/ htmsider/pb0278.htm

www.twi.co.uk/j32k/ getFile/ceramics_hip.html

http://www.sintec-keramik.com/sintec-en/hip-products.html www.thrive-metal.com/ product2.html

www.sv.vt.edu/.../ diffusion/apps/sinter.html

www.sti-us.net/ newdesign.htm

ReferencesReferences

Tapany Udomphol

Documents

Advanced Metal Forming