How can we prevent distortion during heat treatment?

Press quenching is a specialized quenching technique that can be used to minimize the distortion of complex geometrical components during heat treatment.

What causes distortion during heat treatment?

Causes of on-heating distortion

Ultimately, on-heating distortion is the result of phase transformation gradients within the component. Stresses induced during phase transformations can result in the local yield strength of the material to be exceeded and therefore an appreciable change in shape.

What is distortion in heat treatment?

Shape Distortion (warpage) as a result of heat treatment is a result of processing or design issues rather than the expected phase changes of the material. Rapid heating can cause stresses to develop in parts because of excessive temperature gradients.

How do you prevent heat treatment scaling?

To prevent scaling and decarburization, care is taken to apply a uniform coating layer on the component. The coating also reduces decarburization on billets and ingots during hot-forging and hot-rolling operations. Heat transfer from the heating medium to the metal is unaffected by the coating.

Which heat treatment process is most susceptible to creating distortion problems?

Quenching is perhaps the area in a heat-treat operation where the problem of distortion will occur.

Heat Treating With The Heat Treat Doctor, Dan Herring: Managing Distortion

How can you prevent the distortion during quenching in thin parts?

The amount of distortion encountered depends strongly on the nature of the heat treating process that is used. In order to minimize distortion related issues during quenching, heat should be extracted from the component in as uniform a manner as possible.

What can go wrong during heat treatment?

MOST OF THE PROBLEMS in heat- treated parts are attributed to faulty heat- treatment practices (such as overheating and burning, and nonuniform heating and quench- ing), deficiency in the grade of steels used, part defect, improper grinding, and/or poor part design.

What is scaling during heat treatment?

Scale —the dark brown- or black-colored flaky material often observed on the surface of a part when exposed to high heat— is more than just unsightly. Often, parts require additional machining after they're heat treated, and if heat treat scale isn't removed, it can flake off during machining.

What causes scaling on steel?

Unlike rust, which forms over a long period of exposure to oxygen and moisture, scale forms on all steel and iron products that are hot rolled. The only way to prevent its appearance would be to manufacture them in an inert atmosphere. Mill scale is not in itself harmful to the workpiece.

What is heat treat scale?

Heat treating steel parts is often specified to change the physical properties of the metal. The extreme heating and subsequent cooling creates a thin layer of scale/discoloration (see part on left of picture) on the surface that needs to be removed.

In which quenching medium the chances of distortion is minimum?

Gas or air quenching will provide the least distortion and may be used if the steel has sufficient hardenability to provide the desired properties.

What should be added in alloy steel to remove distortion in quenching?

Slow (15-20 second) oils are used where hardenability of steel is high enough to compensate for the slow cooling aspects of this medium. All of these oils are used when quenching carburized and carbonitrided parts.

During which of the following heat treatments are the components likely to have distortion warping quench cracks and thermal stresses?

Quenching Media

This severe cooling rate causes excessive internal stresses within the material which results in distortion or quench cracks within the steel.

What is thermal distortion?

Thermal distortion is the deflection/flex, or compressibility of a material under temperature and pressure. Both brake discs and calipers can flex and change shape when subject to excessive temperatures and pressures (load).

How will a metal distort when heated?

When a weld is laid it is molten metal and therefore hot, as it cools it shrinks, this shrinkage imposes stress on the weld and the parent material near the weld. Distortion is also created by localised heating of the base metals which causes local expansion and contractions during the welding operation.

What is 9 point study in heat treatment?

A 9 points study conducted on the charge to measure and find out the amount of distortion occurred after the quenching process.

How do you prevent steel Decarburization?

Decarburisation can be prevented by heat treatment in an intert atmosphere, by wrapping the component in stainless steel foil, or by painting with an isolating paint.

How do you remove scale from steel?

What method can be used to control scale and corrosion?

The tendency to corrode can be eliminated by increasing pH, temperature, hardness, and/or alkalinity. The tendency to scale can be eliminated by decreasing pH, temperature, hardness, and/or alkalinity.

What temperature does scale form on steel?

During hot strip processing, tertiary scale forms on the steel sur- face after descaling or between each mill stand, at temperatures below 1000 °C.

What is scale on heated steel?

Mill scale is a type of iron oxide that is formed on the surface of the steel during the hot-rolling process. The very high surface temperature combined with high roller pressures result in a smooth, bluish grey surface.

Does vinegar remove forge scale?

Vinegar Method

A vinegar soak will remove scale and speed up the finishing process. Soak the knife overnight in household vinegar -- the entire workpiece needs to be immersed or it will etch where air meets vinegar. Use a baking soda bath to neutralize, then dry. The surface should now be ready for sanding.

Why do we do annealing solutions?

Solution Annealing is a heat treatment process which alters the metallurgical structure of a material to change its mechanical or electrical properties. Typically, this process is used to decrease metal crack sensitivity of aged material that needs to be returned to a weldable state.

What are the major factors considered during heat treatment of steel?

These factors are (i) heat conductivity of the steel, (ii) the condition of the steel, and (iii) the size and the cross-section of the steel. The heat conductivity of the steel is an important factor. The steel with high-heat conductivity is heated up at a faster rate than one with a low conductivity.

What are the five basic heat treatment process?

Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering, carburizing, normalizing and quenching.