|Work Piece Material||Steel|
|Running Duration||8 Hours|
|Post Weld Heat Treatment Equipment||Post Weld Heat Treatment Cooperheat|
|Post Weld Heat Treatment Consumables||Preheater With Magnets|
|Types of Potential Treatment||Post Heating|
|Techniques of Heat Treating||Annealing|
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. A STEEL is usually defined as an alloy of iron and carbon with the carbon content between a few hundreds of a percent up to about 2 wt%. Other alloying elements can amount in total to about 5 wt% in low-alloy steels and higher in more highly alloyed steels such as tool steels and stainless steels.
Steels can exhibit a wide variety of properties depending on composition as well as the phases and microconstituents present, which in turn depend on the heat treatment.STRESS-RELIEF HEAT TREATING
is used to relieve stresses that remain locked in a structure as a consequence of a manufacturing sequence. This definition separates stress-relief heat treating from post weld heat treating in that the goal of post weld heat treating is to provide, in addition to the relief of residual stresses, some preferred metallurgical structure or properties. For example, most ferritic weldments are given post weld heat treatment to improve the
fracture toughness of the heat-affected zones (HAZ). Moreover, austenitic and nonferrous alloys are frequently posting weld heat treated to improve resistance to environmental damage. Stress-relief heat treating is the uniform heating of a structure, or portion thereof, to a suitable temperature below the transformation range, holding at this temperature for a predetermined period of time, followed by uniform cooling. Care must be taken to ensure uniform
cooling, particularly when a component is composed of variable section sizes.
If the rate of cooling is not constant and uniform, new residual stresses can result that is equal to or greater than those that the heat-treating process was intended to relieve. Stress-relief heat treating can reduce distortion and high stresses from welding that can affect server performance. The presence of residual stresses can lead to stress-corrosion cracking (SCC) near welds and in regions of a component that has been cold strained during processing.
Furthermore, cold strain per se can produce a reduction in creep strength at elevated temperatures. Residual stresses in a ferritic steel cause a significant reduction in resistance to brittle fracture. In a material that is not prone to brittle fractures, such as an austenitic stainless steel, residual stresses can be sufficient to provide the stress necessary to promote SCC even in environments that appear to be benign.NORMALIZING OF STEEL
is a heat-treating process that is often considered from both thermal and microstructural standpoints. In the thermal sense, normalizing is an austenitizing heating cycle followed by cooling in still or slightly agitated air. Typically, the work is heated to a temperature of about 55 °C (100 °F) above the upper critical line of the iron-iron carbide phase diagram. To be properly classed as a normalizing treatment, the heating portion of the process must produce a homogeneous austenitic phase (face-centered cubic,
or fcc, crystal structure) prior to cooling.