Forming

Forming Processes

General Manufacturing Processes Engr.-20.2710 Instructor - Sam Chiappone

Deformation Process ●

●

Permanent (plastic) deformation of a material under tension, compression, shear or a combination of loads. Types of Deformation – – – –

Bulk flow in (3) dimensions Simple shearing of material Compound to simple bending Combination of above

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Deformation Process ●

Stresses used to produce change – – – –

●

Tension Compression Shear Combination in multiple axis

(2) Classifications – Bulk = Significant change in surface area, thickness and cross section reduced, and overall geometry changed. – Sheet = Some deforming of material, but initial material thickness remains the same Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Deformation Process

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Deformation Process

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Deformation Process

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Deformation Process

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Process Variables ●

(3) Classification – Independent » Controlled by the engineer

Figure 15-1 Schematic representation of a metalforming system showing independent variables, dependent variables, and the various means of linking the two.

– Dependent » Process determines outcome

– Independent / Dependent

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Work Ranges

●

(2) Types of mechanical work where material undergoes plastic deformation ● ●

Hot Working (HW) Cold Working (CW)

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Definition of HW vs. CW ● ●

HW is performed above the recrystallization temp of the material and CW is done below the recryllization temp of the material. Recystallization Temp- “The approximate minimum temp at which complete recyrallization of a cold worked metal occurs within a specified time.” -Heat Treaters’s Guide, American Society for Metals »

Approximate temperature ranges – HW- .6 melt temp. – WW - .3-.6 melt temp. – CW - less than .3 melt temp. –

Example - CRS 950-1300F –

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Definition of HW vs. CW ●

Approximate temperature ranges – HW - .6 melt temp. of the material – WW - .3 to .6 melt temp of the material – CW - less than .3 of the material » Example - 1020 CRS 950 - 1300F

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Hot Working ●

●

When HW a metal is in a plastic state and is easily formed. The forces required to deform the metal are less than CW. Some mechanical properties of the metal are improved due to process characteristics. At elevated temperatures, metal microstructures are rebuilding continually through the recrystallization process which allows for much higher deformation.

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Advantages to HW ● ●

● ●

Porosity in metal is largely eliminated Impurities (inclusions) are broken up and distributed through the metal Course grains are refined Due to grain refinement, the physical properties are generally improved » Ductility and resistance to impact are improved » Strength is increased Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Advantages to HW

Figure 15-3 Cross section of a 4-in.diameter case copper bar polished and etched to show the as-cast grain structure.

Rensselaer Polytechnic Institute

Figure 15-4 Flow structure of a hot-forged gear blank. Note how flow is parallel to all critical surfaces. (Courtesy of Bethlehem Steel Corporation, Bethlehem, PA.)

GMP-20.271 Chiappone

Advantages to HW ●

●

Amount of energy necessary to change the shape of the raw material in a plastic state is far less than if the material was “cold.” Economical compared to CW

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Disadvantages to HW ●

● ●

High working temp. can result in rapid oxidation/scaling of surface = poor surface finish Generally, close tolerances are hard to control Equipment and tool maintenance costs are high

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Primary HW Processes ● ● ● ● ●

Rolling Forging Extrusion Pipe & tube manufacturing Drawing

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Rolling ●

Heated metal is passed between rotating rolls to reduce the cross-section.

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Rolling ●

●

One of the primary first process to convert raw material into finished product. Starting material (Ingots) are rolled into blooms, billets, or slabs by feeding material through successive pairs of rolls. » Bloom - square or rectangular cross section with a thickness greater than 6” and a width no greater than 2x’s the thickness » Billets - square or circular cross section - - smaller than a bloom » Slabs - rectangular in shape(width is greater than 2x’s the thickness), slabs are rolled into plate, sheet, and strips.

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Forging ●

The plastic deformation of metals, typically at elevated temperatures, using compressive forces exerted through a die to conform the metal to a desired shape.

●

Process advantages: – Closing of voids in the metal – Reduced machining time – Improve the physical properties of the starting metal Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Forging ●

Process disadvantages: – Possible scale inclusions in forging – Tooling cost can be high – Usually not used for short production runs

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Forging Methods ●

Open-Die Drop Hammer - heated metal is placed between dies—a force is delivered with a steam hammer. – Accuracy is not good – Complicated shapes are difficult to produce

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Forging Methods

Open-Die Drop Hammer - Steam Hammer Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Forging Methods

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Forging Methods ●

Upset forging – Grip a bar—heat the end—forge into desired shape » Product examples ● Bolts ● Engine valves

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Forging Methods ●

Impression Die Drop Hammer Forging - Hot pliable metal is forces into the shape of closed impression dies. This process is typically performed in a progressive method through a series of dies to control the flow. – 2 Types of drop forge hammers » Steam » Gravity

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Forging Methods

Impression Die Drop Hammer Forging Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Forging Methods Figure 16-12 Impression dropforging dies and the product resulting from each impression. The flash is trimmed from the finished connecting rod in a separate trimming die. The sectional view shows the grain flow resulting from the forging process. (Courtesy of Forging Industry Association, Cleveland, OH.)

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Forging Methods ●

Press Forging – Large….thick work – Slow Squeezing action penetrates entire work piece producing uniform deformation – Dies are typically heated to: » Assist surface flow » Reduce surface heat loss » Assist in obtaining close tolerances and surface finish

– Two types of presses -- mechanical and hydraulic » Hydraulic - up to 50,000 tons

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Forging Methods ●

Press Forging

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Hot Extrusion ●

●

A plastic deformation process in which metal is forces under pressure to flow through a single, or series of dies until the desired shape is produced. Advantages – – – – – –

Wide variety of shapes High production rates Improved microstructure and physical properties Close tolerances are possible Economical Design flexibility

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Hot Extrusion

Figure 16-25 Direct extrusion schematic showing the various equipment components. (Courtesy of Danieli Wean United, Cranberry Township, PA.)

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Typical Extruded Products

Figure 16-26 Typical shapes produced by extrusion. (Left) Aluminum products. (Courtesy of Aluminum Company of America, Pittsburgh, PA.) (Right) Steel products. (Courtesy of Allegheny Ludlum Steel Corporation, Pittsburgh, PA.)

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Pipe, Tube, and Wire Manufacturing •Tube - Butt or electric welding and Piercing

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Pipe, Tube, and Wire Manufacturing •Wire Drawing

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Drawing ●

Flat sheet or a plate of metal is forced into a recess with a depth more than several times the starting materials thickness.

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Cold Working ●

●

●

CW is done below the recrystallization point of the material. In CW, greater forces are required to transform the raw metal into the desired shape. One major advantage…..as the grain deformation proceeds greater resistance to the action is building resulting in improved strength and hardness (strain hardness). CW is a high volume production process.

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Cold Working ●

Similar processes as HW—major differences include – Forces required – Temperature range – Equipment specifications

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Advantages & Disadvantages ●

Advantages – No heat required – Better surface finish – Superior dimensional control---little or no secondary operations – Strength, fatigue, and wear properties are improved – Improved machinability

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone

Advantages & Disadvantages ●

Disadvantages – – – –

Increased stress in material—strain hardening Greater force required to work raw material Heavier and more powerful equipment is required Undesirable stresses may be produced in final product

Rensselaer Polytechnic Institute

GMP-20.271 Chiappone