Working Sheet MetalMohd. Hafizin Jamil Bin Rashidi

Muhammad Irfan Bin Mohd Noor

Topic OutlinesAutomotive Sheet MetalTypes of Body DamageClassifying Body DamageUnderstanding MetalMetal Straightening TechniqueMetal Shrinking, Stress RelievingWorking Aluminum PanelPaintless Dent Removal

AUTOMOTIVE SHEET METALGETTING TO KNOW ABOUT METAL.

What is a sheet metal?Sheet metal is metal formed by an industrial

process into thin, flat pieces.It is one of the fundamental forms used in

metalworking and it can be cut and bent into a variety of shapes.

Extremely thin thicknesses are considered as foil or leaf, and pieces thicker than 6mm(0.25 in) are considered as plates.

The most common sheet metal used in automotive to make bodies is steel. It is reasonably cheap and easy to press into shape to make body parts.

The next best is aluminum. It is lighter but harder to bend into tight shapes without cracking. It is also harder to weld in mass production.

What metals are used in automotive?

There are three types of steel used in the automotive body and only two are commonly used.

The first type which is used by Volvo™ is boron steel which is stronger than the other two types of steel.

The two types commonly used are: Mild and low-carbon steel Higher carbon steel

Steel and it’s types..

Boron steel is developed using boron as an alloying element in developing Ultra High-Strength Steel(UHSS).

Once bent, it can’t be straightened and it requires replacement if damaged.

Boron steel are also sensitive to heat and it weakens when it’s heated rapidly.

Because of its sensitivity to heat, it can’t be galvanized. Therefore, corrosion protection is crucial and essential after welding.

More on Boron Steel…

Also called plain-carbon steel, is the most common form of steel because of its price is low while it provides material properties that are acceptable for many applications, more so than iron.

Contains approximately 0.05-0.3% carbon making it malleable and ductile.

Mild steel has a relatively low tensile strength, but its cheap and malleable; surface hardness can be increased by carburizing.

Note:

Carburizing is a heat treatment process in which iron or steel absorbs carbon liberated when the metal is heated in the presence of carbon bearing material, such as charcoal or carbon monoxide with the intent of making the metal harder.

More on Mild and Low-Carbon Steel…

Carbon steels which can successfully undergo heat treatment have a content in the range of 0.3-1.7% by weight.

Medium carbon steel: approximately 0.3-0.59% carbon content. (Balances ductility and strength and has good wear resistance)

High-carbon steel: 0.6-0.99% carbon content. (Very strong)

Ultra-high-carbon steel: 1.0-2.0% carbon content. (Steels that can be tempered to great hardness)

More on High-Carbon Steel…

6111 aluminum and 2008 aluminum alloy are extensively used for external automotive body panels, with 5083 and 5754 used for inner body panels.

Hoods have been manufactured from 2036, 6016, and 6111 alloys.

Truck and trailer body panels have used 5456 aluminum.

Automobile frames often use 5182 aluminum or 5754 aluminum formed sheets, 6061 or 6063 extrusions.

Aluminum and it’s types…

2000 series(2008,2036) – alloyed with copper, can be precipitation hardened to strengths, comparable to steel. Formerly referred as duralumin, they were once the most common aerospace alloys, but were susceptible to stress corrosion cracking and are increasingly replaced by 7000 series in new designs.

5000 series(5083,5754,5456,5182) – alloyed with magnesium.

6000 series(6111,6016,6061,6063) – alloyed with magnesium and silicon, are easy to machine, and can be precipitation hardened, but not to the high strengths that 2000 and 7000 can reach.

Continued…

TYPES OF BODY DAMAGEKNOWING BODY DAMAGE

Types of body damageWhen determining the kind of repair procedures, we

must determine the construction of the damaged panel; angle of impact; speed of the impact object; and size, rigidity and weight of the impact object.

You must be able to visualize how the metal folded during impact.

Body damage can be separated into five types: Simple bends Displaced areas Rolled buckles Stretches Upsets

Continued…Simple bends are bends in the metal such as minor

dings and bumps, and damage in which high stress is not a factor.

Displaced areas are metal sections that have been moved but not otherwise damaged.

Rolled buckles or S-shaped bends, are pronounced displaced areas with the metal folded or tucked under itself.

Stretches are caused by tension rather than compression.

Upsets happen when opposing forces push against an area, causing it to yield. Caused by compression rather than tension, this is sometimes called accordion pleat.

CLASSIFYING BODY DAMAGEHOW TO CLASSIFY BODY DAMAGE

Classifying body damageThere are three conditions where metal is

damaged by impact: Direct damage – a tear, gouge or scratch Indirect damage – buckle (a fold or hinge in

metal due to damage or tension) or pressures(unwanted force due to impact damage.

Work hardening – normal and impact created.

Direct damage is a simple, visible damage and easy to find; i.e gouge, tear, scratch.

It is the damaged portion of the panel that came in direct contact with the object that caused the impact.

The damage is usually about 20% of the total damage and the repair at the point of impact is limited.

Usually requires some body filler or, on rare occasions, lead, after all indirect damages have been handled.

Direct damages varies from job to job.

Direct damage

Indirect damages are caused by the shock of collision forces travelling through the body and inertial forces acting on the rest of the unibody.

It is hard to completely identify and analyze.It is also can be found anywhere on the

vehicle.Indirect damage represents on the average of

10-20% of the overall damages.

Indirect damages

Work hardening occurs when plastic deformation has caused the metal to become very hard in the bent area.

As the metal is worked to its limit, it becomes harder and harder.

With this increase in hardness, there is an increase in strength and stiffness as a result of work hardening.

Work hardening

UNDERSTANDING METALWHAT YOU SHOULD KNOW ABOUT METAL

Understanding metalThere are three properties of sheet metal that

is needed to be familiarize with to do quality bodywork:PlasticityWork hardeningElasticity

Continued…Plasticity is the property that allows metal to

be reshaped when enough force is applied to it. This is the same property that allowed it to be stamped into a fender, hood or door.

Work hardening or cold working occurs when metal is bent, stretched, shaped or moved. How much a piece of metal can be cold-worked has a limit, after which, it will break.

Elasticity is the property of metal that allows it to regain it’s original shape after being deflected.

METAL STRAIGHTENING TECHNIQUETECHNIQUES TO STRAIGHTEN METAL THAT NEEDS

TO BE MASTERED

What are the techniques available?There are a few techniques that we can learn

theoretically. However, learning by methodically is most preferred since the techniques would be much better off by doing it.

The techniques available to straighten metal are: Using body hammer Hammer-on-dolly Hammer-off-dolly Picking dents Straightening with spoon Using rubber air bladders Straightening with suction cups Straightening with studs

The body hammer is often used to remove small dents in sheet metal parts.

It is designed to strike the sheet metal and rebound of the surface.

Minor low and high spots in sheet metal can often be fixed with a body hammer.

The secret of metal straighteningis to hit the right spot at the right time, with the right amount of force.

Using body hammer

A method to exert a powerful but concentrated smoothing force to a small area on a damaged panel.

The dolly is held against the back of the damage and the hammer hits the metal right over the top of the dolly.

This exerts a pinching force on the metal between the dolly and the hammer head.

Hammer-on-dolly

Is used to raise low spots and lower high spots simultaneously.

The hammer hits the panel slightly to one side of where the dolly is being held.

It is often used to rough out or shape large areas of damage during initial straightening.

Hammer-off-dolly

Often involves final straightening of very small areas of damage with the pointed end of a body hammer or with long rod that has a curved, pointed tip.

A pointed head or pick on a hammer is often used to mower small high spots during final straightening of a panel.

All high spots must be lowered to be even or slightly below the original contour to allow application of body filler.

Picking dents

Spoons can be used in a number of ways to straighten sheet metal.

They can be used to pry out dents and certain kinds can be struck with a hammer to drive out dents.

In hard-to-reach areas, a spoon can be used as a dolly, some are even designed to be used in place of a hammer.

Spoons are handy when a dollycannot be held on the back of apanel.

Straightening with spoon

Are designed to push out larger sized dents from the back of panels.

The air bladder can be installed inside doors, quarter panels, and other unibody areas to push out large dents.

Using rubber air bladder

A suction cup can be used to straighten shallow dents.

Wet the area and install the cup. If handheld, pull straight out on the cup’s handle. If mounted on a slide hammer, use a quick blow to pop the dent out.

A vacuum suction cup uses a remote power source(separate vacuum pump or air compressor air flow) to produce negative pressure(vacuum) in the cup.

This increases the pulling power because the cup will be forced against the panel tightly. Larger, deeper dents can be straightened with a vacuum suction cup.

Straightening with suction cups

A stud spot welder joins “pull rods” on the surface of a panel so that drilling holes are not needed.

It is one way to straighten dents. Straightening with spot-welded studs avoids

drilling or punching through the metal and undercoating, which can lead to corrosion.

Straightening with studs

Don Taylor and Larry Hofer. Paint & Body Handbook. Penguin. 1994. Print.

James E. Duffy and Robert Scharff. Automotive Body Repair Technology. 4th ed. Cengage Learning. 2003. Print.

James E. Duffy. I-Car Professional Automotive Collision Repair. Cengage Learning. 2000. Print.

REFERENCE