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Topic: Heat affected zone


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In the News (Sat 25 Oct 14)

  
  Drive shaft assembly and method - Patent 4087593
The welded assembly is then heat treated by bringing the assembly to the austenite phase, uniform throughout the assembly, quenching the assembly in a vertical position, and thereafter tempering the assembly at a temperature uniform throughout to the desired hardness.
In this manner, the non-uniform structures in the heat affected weld zone are made homogeneous, thereby producing favorable distribution of strength characteristics and residual stresses throughout the entire assembly.
Heating of the assembly is preferably done in a neutral atmosphere, such as a nitrogen or exothermic atmosphere, to minimize oxidation.
www.freepatentsonline.com /4087593.html   (2737 words)

  
 [No title]   (Site not responding. Last check: 2007-08-09)
One disadvantage of the laser ablation process is that a heat affected zone is left behind where molten material re-solidified in situ or where material was sufficiently heated and cooled rapidly enough to result in embrittlement.
The size of the heat affected zone is a function of the laser pulse duration and the material parameters such as thermal conductivity and specific heat.
The heat affected zone will depend on the distance the heat is conducted within the material and varies with material and laser wavelength.
www.me.mtu.edu /~microweb/chap4/ch4-3.htm   (445 words)

  
 Mechanical stress improvement process - Patent 4612071
By "heat-affected zone" we mean that portion of the piping immediately adjacent to the weld metal wherein the temperature rise during welding affects the grain structure of the metal of said piping.
The "adjacent base metal" is that portion of the piping immediately adjacent to the heat-affected zone extending axially away from the heat-affected zone a distance not exceeding 2.0.sqroot.Dt, where t is the wall thickness of the piping, and D is the piping diameter.
The plastic deformation induced in the metal by welding heat is the principal cause of residual stresses in weldments.
www.freepatentsonline.com /4612071.html   (1310 words)

  
 Heat-affected zone - Wikipedia, the free encyclopedia
The cross-section of a welded butt joint, with the darkest gray representing the weld or fusion zone, the medium gray the heat affected zone, and the lightest gray the base material.
The heat-affected zone (HAZ) is the area of base material, either a metal or a thermoplastic, which has had its microstructure and properties altered by welding or heat intensive cutting operations.
The efficiency is dependent on the welding process used, with shielded metal arc welding having a value of 0.75, gas metal arc welding and submerged arc welding, 0.9, and gas tungsten arc welding, 0.8.
en.wikipedia.org /wiki/Heat-affected_zone   (330 words)

  
 Fracture Toughness Behavior of Weldments with Mis-Matched Properties at Elevated Temperature
The width of the heat affected zone, the distance from the fusion line to the end of the recrystallized grains, was approximately 1.85 mm (0.073 in) for all weldments.
The coarse grain region of the heat affected zone was either non-existent or negligible in all specimens and a structure consisting of martensite and bainite was observed in its place.
The heat affected zone consists of a region with considerable variability in the microstructure and mechanical properties of welds.
www.tms.org /Students/Winners/Cretegny/Cretegny.html   (3863 words)

  
 THE EFFECT OF A LONG POST WELD HEAT TREATMENT ON THE INTEGRITY OF A WELDED JOINT IN A PRESSURE VESSEL STEEL
For the HAZ, thin foils for the transmission electron microscope (TEM) were prepared from specimens of the five simulated HAZ microstructures in the as-simulated condition and after 40 h of PWHT.
Therefore, the integrity of a joint produced by high heat input welding seems to be dependent on the toughness of the HAZ and not on the weld metal.
The width of the HAZ increased with increase in the heat input.
www.pkn.co.za /pap-QTWSD.html   (2677 words)

  
 Starter Topic - Welding of Stainless Steels - Corrosionsource.com Discussion Boards
The austenitic stainless steels are susceptible to chromium carbide precipitation in the heat affected zone which occurs between 420 degrees and 870 degrees Celsius.
These steels can be welded in any heat treated condition, (annealed(a), hardened(b), stress relieved(c), or tempered) because the heat treated condition has little affect on the behaviour of the heat affected zone hardening and thus the weldability.
Heat input must be carefully controlled to minimize dilution to obtain the desired level of austenite in the deposit.
www.corrosionsource.com /discuss2/ubb/Forum34/HTML/000001.html   (1887 words)

  
 Application Experiences with Laser Beam Welding
In low-carbon steel the welding zone is martensitic and exhibits increased hardness, the level of which depends upon carbon and alloying elements contents.
Specific laser beam welding features, such as high welding speed, small heat-affected zone, and low material exposure at elevated temperatures are beneficial for welding this type of steel, because prolonged periods at high temperatures may lead to chromium precipitation on grain boundaries and reduction of corrosion resistance.
The function of trailing and back-up shield coverage is to shroud the weld and adjacent hot material with inert gas until the surface temperature cools to 300°-400°C. Dendrite structure of the weld zone in a cross section is a good indication of improper shielding.
www.alspi.com /lsrweld.htm   (1489 words)

  
 Gear Solutions Online: Features: Laser Heat Treating Advances for the Gear Industry By Joel DeKock, Ph.D., September ...
Laser heat treating is the most common process in the group of surface modification techniques that include alloying, glazing, and cladding.
When heat treated material absorbs the beam, the beam intensity must be powerful enough so that the energy absorbed is greater than the energy conducted away.
Figure 1, material under the beam is affected by the laser energy, resulting in two heat-affected regions: the hardened case, and the heat affected zone.
www.gearsolutionsonline.com /articles/laser0904.html   (1948 words)

  
 What is Preheat?| Lincoln Electric
Although it is important that the work be heated to a minimum temperate, it is acceptable to exceed that temperature by approximately IOOF (40C).
When heating the joint to be welded, the AWS D1.1 code requires that the minimum preheat temperature be established at a distance that is at least equal to the thickness of the thickest member, but not less than 3 in.
To ensure that the full material volume surrounding the joint is heated, it is recommended practice to heat the side opposite of that which is to be welded and to measure the surface temperature adjacent to the joint.
www.lincolnelectric.com /knowledge/articles/content/preheat.asp   (1233 words)

  
 Bioline International Official Site (site up-dated regularly)
In the heat-affected zone, the width of the tempered zone increases with increasing modulation frequency and the microstructure is refined.
Ultrasonic  vibration accelerated heat conduction and changed thermal circle in the weld so that the cooling rate during solidification was increased with ultrasonic treatment, which means that when the metal temperature is above Ac3 the time is shortened, and which reduces the grain size in the partially melted zone.
The temperature gradient between the compressing and expanding areas causes heat transfer in the matrix to flow from the higher temperature area to the lower temperature area, which accelerates heat transfer, changes the temperature distribution, and increases the HAZ.
www.bioline.org.br /request?ts01099   (1659 words)

  
 REPAIR OF ALUMINUM STRUCTURES   (Site not responding. Last check: 2007-08-09)
When we consider the controlled heat treatment that has been conducted on these materials prior to welding, in order to obtain the -T6 condition, we can appreciate their response to the arc welding process, which heats the material to the same temperatures in an uncontrolled manner.
There is a direct association between the total welding heat input and mechanical properties of the base material adjacent to the weld (the heat affected zone) after welding.
A major contributor to the overall heat input of a weld is the travel speed during the welding process.
www.alcotec.com /qanda1.htm   (799 words)

  
 Friction Stir Weld Microstructure
We have seen that there are three zones to consider in the microstructure of a friction stir weld: the heat-affected zone, the thermomechanically affected zone, and the stir zone.
The microstructural variations are due to the heterogeneous nature of the deformation and thermal histories within the stir zone, with dynamic recrystallisation occurring during welding.
(a) Heat affected zone; (b) thermomechanically affected zone showing a deformed microstructure; (c) transition from the thermomechanically affected zone to the stir zone.
www.msm.cam.ac.uk /phase-trans/2003/FSW/bbb.html   (316 words)

  
 CMS—Welding Science   (Site not responding. Last check: 2007-08-09)
Surrounding the fusion zone is a heat-affected zone, where the substrate is heated to temperatures up to the melting point of the metal being joined.
Solidification in the fusion zone and solid-state phase transformations in the heat-affected zone are responsible for dramatic changes in the microstructure and properties of the welded joint.
Solid-state phase transformations that occur in the HAZ create gradients of both microstructure and properties between the liquid metal in the fusion zone and the unaffected base metal farthest from the weld.
www-cms.llnl.gov /s-t/welding.html   (2909 words)

  
 Microstructural change in high-temperature heat-affected zone of low-carbon weldable 13% Cr martensitic stainless steels   (Site not responding. Last check: 2007-08-09)
The microstructures that develop in the high temperature heat-affected zone (HT-HAZ) of single-pass tungsten inert gas welded plates of two different low carbon martensitic stainless steels have been investigated using optical microscopy and energy dispersive X-ray microanalysis.
The region containing delta-ferrite was found to be larger in the HAZ of the highest alloyed steel.
Evidence of former Widmanstatten austenite structure was found in the weld metal and in the grain coarsened heat-affected zone of the highest alloyed steel.
www.msm.cam.ac.uk /phase-trans/2003/dominique.html   (119 words)

  
 Untitled Document   (Site not responding. Last check: 2007-08-09)
5) The depth of the heat-affected zone or recast structure on the surface is approximately proportional to the magnitude of the energy impinging on that surface.
Whenever EDM is used in the manufacture of highly stressed structural parts, the heat affected layer which is produced should be removed or given a remedial post treatment.
For critically loaded surfaces, it is desirable to move the HAZ or to modify preparation or to conduct extensive testing to assess the reliability of the surface generated for particular applications.
www.unl.edu /nmrc/Diesinking/surfaceint/surface.htm   (2074 words)

  
 Microstructure Classification of Friction Stir Welds
Heat affected zone (HAZ): In this region, which clearly will lie closer to the weld centre, the material has experienced a thermal cycle which has modified the microstructure and/or the mechanical properties.
The term heat affected zone is now preferred, as this is a direct parallel with the heat affected zone in other thermal processes, and there is little justification for a separate name.
Thermo-mechanically affected zone (TMAZ): In this region, the material has been plastically deformed by the friction stir welding tool, and the heat from the process will also have exerted some influence on the material.
www.twi.co.uk /j32k/unprotected/band_1/fswqual.html   (670 words)

  
 Titanium - Welding of Titanium and Titanium Alloys
In a welding operation involving a titanium based material, the fusion zone and part of the heat affected zone are heated to temperatures above the beta transformation temperature and on completion of the welding cycle these cool through the beta transus to ambient temperature.
On cooling, transformation of the beta phase present in the weld and heat affected zones takes place and it is the form and consequently the properties of the transformation product that dictate whether or not the material can be regarded as fully weldable.
Hardness of the weld zone relative to the parent metal is increased with increasing supersaturation, a change accompanied by a corresponding deterioration in weld ductility, toughness and bend performance.
www.azom.com /details.asp?ArticleID=883   (593 words)

  
 Bi-Metal Unique Saw Technology - The L.S. Starrett Company
The heat-affected zone is a stressed area that can cause teeth to shear from the carrier.
Caron describes solid-state diffusion bonding as a combination of low heat and high pressure that applies HSS wires to both sides of the carrier with pressure rolls in an inert atmosphere.
In diffusion bonding, with HSS wires bonded to the sides of the strip, the contact area is increased by 170 percent, and the fusion zone is parallel to the teeth.
www.starrett.com /pages/1075_bi_metal_unique_saw_technology.cfm   (1301 words)

  
 Grain Size Distribution in a Gold Ball Bond; Heat-Affected or Recrystallization Zone
The increase in grain size diminishes as the distance from the ball bond increases, because of the corresponding decrease in exposure to the high temperature of the melt.
Eventually, a point in the wire will be reached wherein the grain size is no longer affected by the heat, i.e., the grains still have the original or unaffected grain size.
The heat-affected zone is a 'weak' zone of the bondwire.
www.siliconfareast.com /ball-bond-grains.htm   (403 words)

  
 Wire EDM Heat Affected Zone   (Site not responding. Last check: 2007-08-09)
What this means is that wherever the electrical wire passes to make the cut, heat is a generated by-product of the electrical cut.
The area where the cut is made is known as the heat affected zone.
The negative side effect of having larger wire EDM heat affected zones and more recast is that the machined object has the potential for a loss of precision due to the recast created in the heat affected zone.
www.e-wireedm.com /Wire_EDM_Heat_Affected_Zone.html   (337 words)

  
 Laser Processing of Plastic Sheet: Plastic Distributor & Fabricator
The heat generated through this process produces a selective vaporization and decomposition of the plastic to form an accurate cut.
The laser heats, melts and/or vaporizes materials in the defined "spot", applying heat only where it is needed with a minimal heat-affected zone outside of the focused spot of energy.
This factor is a function of the thermal conductivity or the specific heat and/or thickness of a material.
www.plasticsmag.com /ta.asp?aid=3502   (1346 words)

  
 Corrosion of Welded 316L Stainless Steel Tubes
Thus, it is believed that the evaporation and redeposition of iron, not manganese, negatively impacts the corrosion resistance of welded low-manganese and ultralow-manganese stainless steel alloys in chlorine containing, moist, gaseous atmospheres.
In order to extract weld fume deposits from the inner surface of the weld sticks, each was heated in a convection oven set at 120°F (48°C), capped at one end with a PTFE cap, filled with 5% nitric acid, and allowed to soak for 15 minutes.
The emitted metals redeposit on the colder tube surfaces adjacent to the weld zone.
www.future-fab.com /document.asp?d_id=3726   (2662 words)

  
 HAZ hardness in laser beam welds   (Site not responding. Last check: 2007-08-09)
The thermal profiles that result from a numerical model of laser beam welding are used to calculate the hardness in the heat-affected zone of two 10-mm-thick BS4360 50D steel welds.
The influence of convection, the temperature dependence of material properties and any incomplete information concerning material properties, including the coefficient of surface tension of the liquid metal, is taken into account by the numerical model by means of constrained optimization of the system matrix elements.
The laser beam welds were full penetration welds and were made at two different laser powers at the test piece (4.5 and 9 kW) and two different welding speeds (5 and 20 mm/s), respectively.
www.msm.cam.ac.uk /phase-trans/2000/laser.html   (245 words)

  
 LASERAGE: Benefits of Laser Processing
This precise concentration of intense heat results in a very narrow weld bead with weld penetration control as close as plus or minus.001”.
The heat affected zone (HAZ) is again minimized assuring minimal dimensional distortion.
The availability of such a unique, precision heat source opens the door for the design possibilities of selective heat treating of large, or small steel parts from prototype quantities to high volume production.
www.laserage.com /benefits.html   (379 words)

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