Objectives of Heat Treatments
Haba Stress Engineering

Heat Treatment is the controlled heating and cooling of metals to alter their physical and mechanical properties without changing the product shape. Heat treatment is sometimes done inadvertently due to manufacturing processes that either heat or cool the metal such as welding or forming.

Heat Treatment is often associated with increasing the strength of material, but it can also be used to alter certain manufacturability objectives such as improve machining, improve formability, restore ductility after a cold working operation. Thus it is a very enabling manufacturing process that can not only help other manufacturing process, but can also improve product performance by increasing strength or other desirable characteristics.

Steels are particularly suitable for heat treatment, since they respond well to heat treatment and the commercial use of steels exceeds that of any other material. Steels are heat treated for one of the following reasons:
1. Softening
2. Hardening
3. Material Modification

Common Heat Treatments

4. Softening: Softening is done to reduce strength or hardness, remove residual stresses, improve toughnesss, restore ductility, refine grain size or change the electromagnetic properties of the steel.

5. Restoring ductility or removing residual stresses is a necessary operation when a large amount of cold working is to be performed, such as in a cold-rolling operation or wiredrawing. Annealing full Process, spheroidizing, normalizing and tempering— austempering, martempering are the principal ways by which steel is softened.

6. Hardening: Hardening of steels is done to increase the strength and wear properties. One of the pre-requisites for hardening is sufficient carbon and alloy content. If there is sufficient Carbon content then the steel can be directly hardened. Otherwise the surface of the part has to be Carbon enriched using some diffusion treatment hardening techniques.

7. Material Modification: Heat treatment is used to modify properties of materials in addition to hardening and softening. These processes modify the behavior of the steels in a beneficial manner to maximize service life, e.g., stress relieving, or strength properties, e.g., cryogenic treatment, or some other desirable properties, e.g., spring aging.Parts which have been heavily formed, machined, cut or are fabricated by welding, have high internal stresses. The part or assembly can be made stress free by heating to a certain temperature, where the stresses will be removed by thermal relaxation, without affecting the mechanical properties of the part. The resultant part will be far less prone to warp change dimensions, during further processing or use.

Thermal stress relieving can be performed on various materials, including plastics, aluminiums, steels andalloys.

Maximum load size is 12ft x 6ft x 4ft - 8” high

WHY USE A CONTROLLED PREHEAT?
 Preheating During Welding provides the following benefits:
 Reduces the levels of thermal stress.
 Provides compensation for high heat losses.
 Minimizes the rate of weld hardening.
 Reduced porosity in the weld.
 Reduced hydrogen cracking.
 Improved microstructure of heat affected zone.

THE BENEFITS OF WELD PREHEATING AND REDUCING THERMAL STRESS

PROBLEM:
 Thermal Stresses Occur asMolten Weld Pools Cool
 Cracking Can Occur Both During and After Welding
 Colder ParentMetal Resists the Inevitable Contraction of theWeldMetal

SOLUTION:
 Preheating reduces the temperature difference between the Weld Metal and the Parent Metal andMinimizes Potential Cracking

PRE WELDHEAT TREATING AND HIGH HEAT LOSS

PROBLEM:
 Heavy Wall Materials and Aluminum Alloys with higher thermal conductivity can act as a heat sink, drawing heat away from a weld and cooling at an accelerated rate.
SOLUTION:
 Preheat Heat treatment will reduce the cooling rate of the deposited weld material and allow a proper fusion with the parent metal

PRE WELDHEAT TREATMENT WILL REDUCE WELD PEROCITY
PROBLEM:
 If moisture is present at a welded joint, the high heat of the welding arc will break the water down into its elements, hydrogen and oxygen. The hydrogen by-product easily dissolves into the weld metal and causes weld porosity during weld solidification.
SOLUTION:
 Performing a pre weld heat treat drives away moisture fromthe welded joint.

PRE WELDING HEAT TREATMENTWILL REDUCEWELD HARDENING

PROBLEM:
 During and after completing of the welding process, both the weld pool and the Heat Affected Zone (HAZ) can harden and crack when cooling at a rapid pace
SOLUTION:
 By preheating the weld and the Heat Affected Zone (HAZ) the rate of cooling can be controlled and reduced thereby eliminating problems associated with weld hardening

PRE WELDHEAT TREATING PREVENTHYDROGEN CRACKING

PROBLEM:
 Electrode Coatings and Fluxes can often introduce moisture directly to the arc and weld pool. The increase in moistures increases the possibility of weld or Heat Affected Zone (HAZ) cracking.
SOLUTION:
 Preheating slows down the weld cooling rate which allows hydrogen to escape

WELD PRE HEATING IMPROVES MATERIAL MICROSTRUCTURE

PROBLEM:
 Low Alloy Steels containing elements such as chromium, nickel, molybdenum, and vanadiumare susceptible to cracking in the Heat Affected Zone (HAZ)

SOLUTION:
 Preheating improves the microstructure inside the HAZ by reducing the post weld cooling rate. The reduced cooling rate produces:
 A more desirable and ductile microstructure to be formed
 Minimizes Under Surface Cracking

Refractory-dry out
Combustion Heat Treatment Services

Haba Stress Engineering is a name you can trust for all of your on-site technical service needs. We own and operate the most advanced and dependable fleet of Heat Treatment Equipment available for use in the field today. Combine our advanced equipment technology, the best trained and most knowledgeable Heat Treatment Technicians, and strategic locations of our field service centers and you have a combination that delivers quality results on time and under budget.

ON-SITE FIELD HEAT TREATMENT TECHNOLOGY

COMBUSTION SERVICES AND REFRACTORY DRY OUTS
Refractory Dry Outs Give Your Linings
 Improved Refractory Strength
 Refractory Separation Eliminated
 Removal of Mechanical Water
 Minimize Explosive Spalling
 Avoid Thermal Stress

IMPROVED REFRACTORY STRENGTH
 Near 1000 Degrees F Ceramic Bonding Takes Place.
 High Velocity Burners Apply High Pressure and Heat
 This Ensures Cross-Sectional Ceramic Bonding.
 Increasing Refractory Strength, Resulting in Increased Service Life

REFRACTORY SEPARATION ELIMINATED

PROPER DRYOUTENSURES THAT DUAL COMPONENT LININGSWILL NOT EXPERIENCE SAGGING OR SEPARATION FROM ANCHORED REFRACTORY BY:
 Utilizing hot, cold, and intermediate thermocouples.
 Ensures proper through wall temperature gradients.
 1000 degrees f, ceramic bonding takes place.

REMOVAL OF MECHANICAL WATER

REFRACTORY HEATED TOO QUICKLYOR UNEVENLYMAY:
 Lock moisture in, causing shortened refractory life.
PROPER DRYOUT
 Removes mechanical water at closely controlled temperatures below 600 degrees F.

MINIMIZE EXPLOSIVE SPALLING

CONTROLLED DRY OUTWILL:
 Slowly & safely, force mechanical and chemical water from the refractory lining.
 Avoiding pressure buildup and explosive spalling.

AVOID THERMAL STRESS

CONTROLLED DRY OUTS PREVENT
 Minute cracking
 Thermally induced stress which weakens the refractory.

INDUSTRIES REQUIRING REFRACTORY DRY OUTS
 SteelMills
 Aluminum
 Foundry
 Glass
 Cement
 Ceramic
 Refineries
 Chemical Plants