heat-treat

More about Heat Treatments: Purpose Precautions Preparation Aftercare Risks Resources

Definition

Heat treatments are applications of therapeutic thermal agents to specific body areas experiencing injury or dysfunction.

Description

There are four different ways to convey heat:

• Conduction is the transfer of heat between two objects in direct contact with each other.
• Conversion is the transition of one form of energy to heat.
• Radiation involves the transmission and absorption of electromagnetic waves to produce a heating effect.
• Convection occurs when a liquid or gas moves past a body part creating heat.

Hot packs, water bottles, and heating pads

Hot packs are a very common form of heat treatment utilizing conduction as a form of heat transfer. Moist heat packs are readily available in most hospitals, physical therapy centers, and athletic training rooms. Treatment temperature should not exceed 131°F (55°C). The pack is used over multiple layers of toweling to achieve a comfortable warming effect for approximately 30 minutes. More recently, several manufacturers have developed packs that may be warmed in a microwave over a specified amount of time prior to use.

Hot-water bottles are another form of superficial heat treatment. The bottles are filled half way with hot water between 115–125°F (46.1–52°C). Covered by a protective toweling, the hot-water bottle is placed on the treatment area and left until the water has cooled off.

Electrical heating pads continue to be used, however because of the need for an electrical outlet, safety and convenience become an issue.

Paraffin

Paraffin, a conductive form of superficial heat, is often used for heating uneven surfaces of the body such as the hands. It consists of melted paraffin wax and mineral oil. Paraffin placed in a small bath unit becomes solid at room temperature and is used as a liquid heat treatment when heated at 126–127.4°F (52–53°C). The most common form of paraffin application is called the dip and wax method. In this technique, the patient will dip eight to 12 times and then the extremity will be covered with a plastic bag and a towel for insulation. Most treatment sessions are about 20 minutes.

Hydrotherapy

Hydrotherapy is used in a form of heat treatment for many musculoskeletal disorders. The hydrotherapy tanks and pools are all generally set at warm temperatures, never exceeding 150°F (65.6°C). Because the patient often performs resistance exercises while in the water, higher water temperatures become a concern as the treatment becomes more physically draining. Because of this, many hydrotherapy baths are now being set at 95–110°F (35–43.3°C). There are also units available with moveable turbine jets, which provide a light massage effect. Hydrotherapy is helpful as a warm-up prior to exercise.

Fluidotherapy

Fluidotherapy is a form of heat treatment developed in the 1970s. It is a dry heat modality consisting of cellulose particles suspended in air. Units come in different sizes and some are restricted to only treating a hand or foot. The turbulence of the gas-solid mixture provides thermal contact with objects that are immersed in the medium. Temperatures of this treatment range from 110–123°F (43.3–50.5°C). Fluidotherapy allows the patient to exercise the limb during the treatment, and also massages the limb, increasing blood flow.

Ultrasound

Ultrasound heat treatments penetrate the body to provide relief to inner tissue. Ultrasound energy comes from the acoustic or sound spectrum and is undetectable to the human ear. By using conducting agents such as gel or mineral oil, the ultrasound transducer warms areas of the musculoskeletal system Some areas of the musculoskeletal system absorb ultrasound better that others. Muscle tissue and other connective tissue such as ligaments and tendons absorb this form of energy very well, however fat absorbs to a much lesser degree. Ultrasound has a relatively longlasting effect, continuing up to one hour.

Diathermy

Diathermy is another deep heat treatment. An electrode drum is used to apply heat to an affected area. It consists of a wire coil surrounded by dead space and other insulators such as a plastic housing. Plenty of toweling must be layered between the unit and the patient. This device is unique in that it utilizes the basis of a magnetic field on connective tissues. One advantage of diathermy over various other heat treatments is that fat does resist an electrical field, which is not the case with a magnetic field. It is found to be helpful with those experiencing chronic low back pain and muscle spasms. Prior to ultrasound technology, diathermy was a popular heat therapy of the 1940s–1960s.

— Jeffrey P. Larson, RPT

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tr.v., -treat·ed, -treat·ing, -treats.
To treat (metal, for example) by alternate heating and cooling in order to produce desired characteristics, such as increased hardness; temper.

heat treater heat treater n.
heat treatment heat treatment n.

For more information on heat-treating, visit Britannica.com.

A procedure of heating and cooling a material without melting. Plastic deformation may be included in the sequence of heating and cooling steps, thus defining a thermomechanical treatment. Typical objectives of heat treatments are hardening, strengthening, softening, improved formability, improved machinability, stress relief, and improved dimensional stability. Heat treatments are often categorized with special names, such as annealing, normalizing, stress relief anneals, process anneals, hardening, tempering, austempering, martempering, intercritical annealing, carburizing, nitriding, solution anneal, aging, precipitation hardening, and thermomechanical treatment.

All metals and alloys in common use are heat-treated at some stage during processing. Iron alloys, however, respond to heat treatments in a unique way because of the multitude of phase changes which can be induced, and it is thus convenient to discuss heat treatments for ferrous and nonferrous metals separately. See also Iron; Steel.

Ferrous metals

Annealing heat treatments are used to soften the steel, to improve the machinability, to relieve internal stresses, to impart dimensional stability, and to refine the grain size.

Hardening treatments are used to harden steels by heating to a temperature at which austenite is formed and then cooling with sufficient rapidity to make the transformation to pearlite or ferrite unfavorable.

Some heat treatments are used to alter the chemistry at the surface of a steel, usually to achieve preferential hardening of a surface layer. Carburizing consists of subjecting the steel to an atmosphere of partially combusted natural gas which has been enriched with respect to carbon. In the nitriding treatment, nitrogen diffusing to the surface of the steel forms nitrides. Chromizing involves the addition of chromium to the surface by diffusion from a chromium-rich material packed around the steel or dissolved in molten lead. See also Surface hardening of steel.

Nonferrous metals

Many nonferrous metals do not exhibit phase transformations, and it is not possible to harden them by means of simple heating and quenching treatments as in steel. Unlike steels, it is impossible to achieve grain refinement by heat treatment alone, but it is possible to reduce the grain size by a combination of cold-working and annealing treatments.

Some nonferrous alloys can be hardened, but the mechanism is one by which a fine precipitate is formed, and the reaction is fundamentally different from the martensitic hardening reaction in steel. There are also certain ferrous alloys that can be precipitation hardened. However this hardening technique is used much more widely in nonferrous than in ferrous alloys. In titanium alloys, the β phase can transform in a martensitic reaction on rapid cooling, and the hardening of these alloys is achieved by methods which are similar to those used for steels.

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The use of heat to treat injuries and accelerate recovery. The heat is usually applied to induce feelings of relaxation and comfort, and to increase blood flow through damaged tissue. It is particularly useful for treating injuries that reduce the range of joint movement (e.g. muscle stiffness), but the heat should not be applied immediately after an acute injury because it may increase internal bleeding. Also, heat treatment should not be used while inflammation persists. In addition to treating injuries, heat, sometimes in the form of hot wax or mud packs, is used to reduce weight by inducing perspiration. However, as the weight loss is mostly in the form of water, it will be regained quickly. See also sauna baths.

n

1. subjecting a metal to a given controlled heat, followed by controlled sudden or gradual cooling to develop the desired qualities of the metal to the maximal degree. 2. a process of giving a metal predetermined physical properties by controlled temperature changes.

Heating and cooling a solid metal or alloy in order to produce changes in its physical and mechanical properties.

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The use of heat to treat injuries and accelerate recovery. The heat may be applied superficially or directed to deep tissues. Superficial heat induces feelings of relaxation and comfort. Other therapeutic properties of heat (deep and superficial) include increasing blood flow through damaged tissue, increasing metabolism, and increasing the threshold of sensory nerve endings (therefore, decreasing pain). Heat treatment should not be used immediately after injury, particularly if there is any bleeding. See also diathermy.

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