HTS Honors Prime Contributors
April 5, 2018 Source: ASM International
In 2017, ASM’s Heat Treating Society R&D Committee established a new recognition for the best papers in the heat treat industry each year. To be considered for the ASM Heat Treating Society Prime Contributor recognition, papers must appear in either the HTPro quarterly newsletter or be published in ASM’s Heat Treat conference proceedings.
Continue readingHigh-impact research to be revealed at Heat Treat 2017
October 4, 2017 Source:
More than 125 presentations of original, unpublished work will be delivered when the ASM Heat Treating Society convenes for its 29th conference and exhibition in Columbus, Ohio, October 24-26. The information exchanged in these sessions – as researchers and practitioners share their latest discoveries, theories, and advancements – will have a significant impact on design and manufacturing innovation as well as the fortunes of industry.
One example of the cutting-edge work that will be unveiled is an investigation on the effect of heat treating on additively manufactured medical implants. Additive techniques offer unprecedented design flexibility for dental and orthopedic implants, but the intense heating and cooling spikes associated with direct metal laser sintering can leave the microstructure of titanium – a good bio-material but a poor thermal conductor – in a less than optimum state. To quantify the potential for improvement, researchers evaluated several heat treat processes and measured changes in hardness, residual stress, and corrosion. The promising findings will be shared in a Thursday morning session.
Another significant accomplishment that will be reported is a new method to predict the quenched and tempered hardness of complex steels based on chemistry data. Two researchers, building on prior attempts to calculate hardness as a function of chemistry, have developed a hybrid model that works for mixed microstructure alloys containing less than 0.5wt%Cr. As Cr levels increase, however, other alloying elements such as Mo and V become more influential, compounding the complexity of the problem. The researchers will describe the new method and its limitations on Tuesday morning.
The results of several cross-sector efforts will also be presented, including a paper submitted by a group examining the role of vanadium in induction hardened shafts. Vanadium microalloying is common in carbon steel shafts because it increases load capacity. Induction hardening offers additional benefits, but the presence of vanadium adds uncertainty to the process. Seeking clarity, researchers have obtained evidence that, under certain conditions, vanadium carbonitride precipitates formed during induction reduce austenite in the case/core region but not the case. Retained austenite, characterized by compositional gradients and undissolved carbides, is believed to limit case depth and hardenability.
More than 125 presentations of original, unpublished work will be delivered when the ASM Heat Treating Society convenes for its 29th conference and exhibition in Columbus, Ohio, October 24-26. The information exchanged in these sessions – as researchers and practitioners share their latest discoveries, theories, and advancements – will have a significant impact on design and manufacturing innovation as well as the fortunes of industry.
Continue readingOne Minute Mentor: Tempering Martensitic Stainless Steels
October 17, 2016 Source:
This graph shows AISI Type 410: Effect of tempering temperature on tensile properties. Heated to and held at 1800°F for 30 minutes; oil quenched; tempered 1 to 4 hours. Impact energy test used Izod specimens. Elongation was measured in 2 in.; yield at 0.2% offset.
The nickel-bearing alloys have a restricted upper tempering temperature because of the danger of re-forming austenite, which would then transform to untempered martensite during cooling, requiring a second tempering operation. Intermediate temperatures can lead to temper embrittlement, which is caused by the precipitation of phosphorus and other species, including but not limited to carbides, at prior austenitic grain boundaries. Temper embrittlement is distinct from the precipitation of α', which causes the well-known 890°F embrittlement, which occurs more severely in alloys with higher chromium levels.
Volume 4D, Heat Treating of Irons and Steels ⇒ Heat Treated High-Alloy Steels ⇒ Heat Treating of Martensitic Stainless Steels ⇒ Tempering
This graph shows AISI Type 410: Effect of tempering temperature on tensile properties. Heated to and held at 1800°F for 30 minutes; oil quenched; tempered 1 to 4 hours. Impact energy test used Izod specimens. Elongation was measured in 2 in.; yield at 0.2% offset.
Continue readingOne Minute Mentor: Heat Treating of Martensitic Stainless Steels
October 10, 2016 Source:
The effect of tempering temperature on hardness and tensile properties of high-alloy steels appears to have the same general form as those of low-alloy steel. A serious decrease in notch toughness occurs when tempering between about 750 and 950°F, as illustrated in the graph for Type 410.
The graph shows the effect of tempering temperature on impact properties of AISI Type 410. Impact energy tests used Izod, Charpy V-notch, or Charpy keyhole as indicated. Heat treatment of test specimens: heated to and held at 1750°C for one hour; oil quenched, temperad for four hours at temperature given; air cooled.
Volume 4D, Heat Treating of Irons and Steels ⇒ Heat Treated High-Alloy Steels ⇒ Heat Treating of Martensitic Stainless Steels ⇒ Tempering
The effect of tempering temperature on hardness and tensile properties of high-alloy steels appears to have the same general form as those of low-alloy steel.
Continue readingOne Minute Mentor: Annealing of Austenitic Stainless Steels
June 29, 2016 Source:
The graph shows isothermal precipitation kinetics for detrimental σ/χ phases for the 254 SMO (S31254), 904L, and 317LMN alloys. For comparison, the stability curve for the formation of chromium carbide in type 316 stainless steel is presented.
As the alloying content increases, the time to precipitate these undesirable phases decreases, and the more highly alloyed superaustenitic grades have very limited time (less than a minute) before the onset of precipitation at temperatures in the 1470 to 1700°F range.
Because of this, cooling from the anneal temperature must be controlled to maximize the quench rate and minimize the time in the 1020 to 1920°F temperature range. This is particularly a problem with thick sections, for which rapid cooling rates are difficult to achieve in the center section.
Annealing temperatures for these more highly alloyed austenitic grades tend to be higher than those of the conventional austenitic grades. These high annealing temperatures ensure dissolution of undesirable secondary phases and promote homogenization of as-solidified structures.
Volume 4D, Heat Treating of Irons and Steels ⇒ Heat Treated High-Alloy Steels ⇒ Heat Treating of Austenitic and Duplex Stainless Steels ⇒ Annealing
The graph shows isothermal precipitation kinetics for detrimental ?/? phases for the 254 SMO (S31254), 904L, and 317LMN alloys.
Continue readingOne Minute Mentor: Carburizing Tool Steels
April 22, 2016 Source:
P20 mold steel is seldom carburized for molds used in compression molding, particularly for molding the more abrasive plastics. Carburizing temperatures no higher than 1650°F are recommended for this steel because higher temperatures may impair polishability; otherwise, conventional carburizing practice is used, and molds may be quenched in oil directly from the carburizing temperature. A common working range is 54 to 58 HRC.
The graph shows tempering characteristics of carburized mold steels.
(a) Upper curve represents steel carburized in hardwood charcoal 1675 to 1700°F for 8 hours, air cooled in pack, reheated at 1725 to 1750°F, cooled in air, and tempered. Middle curve represents steel carburized in cast iron chips at 1725 to 1750°F, removed from pack, cooled in air, and tempered.
(b) Surface hardness after heating at temperature for 2 hours in carburizing compound, followed by oil quenching and tempering.
Volume 4D, Heat Treating of Irons and Steels ⇒ Tool Steels ⇒ Heat Treating of Mold Steels and Corrosion-Resistant Tool Steels ⇒ Recommended Heat Treating Practices
P20 mold steel is seldom carburized for molds used in compression molding, particularly for molding the more abrasive plastics.
Continue readingOne Minute Mentor: Quenching of Hot-Work Tool Steels
January 28, 2016 Source:
Hot-work steels range from high to extremely high in hardenability, so it is possible for them to achieve full hardness by cooling in still air. However, this is not recommended, because intense embrittlement occurs after slow cooling from hardening temperature.
Even with those types having the highest hardenability, sections of die blocks may be so large that insufficient hardening results. In such instances, pressurized nitrogen gas (in vacuum furnaces) or an oil quench is required to achieve full hardness. Hot-work steels are never water-quenched. The figure shows the Continuous Cooling Transformation (CCT) diagram for AISI 6F3.
Volume 4D, Heat Treating of Irons and Steels ⇒Tool Steels ⇒ Heat Treating of hot-Work Tool Steels ⇒ Heat Treatment of H Series and Low-Alloy Hot-Work Steels
Hot-work steels range from high to extremely high in hardenability, so it is possible for them to achieve full hardness by cooling in still air. However, this is not recommended, because intense embrittlement occurs after slow cooling from hardening temperature.
Continue readingOne Minute Mentor: Tempering F Tool Steels
December 11, 2015 Source:
Because of their tungsten content, F-steels form hard tungsten carbides. In combination with the usual heat treatment procedures, they exhibit the highest hardness of all low-alloy cold-work tool steels, both in the as-quenched condition and at low tempering temperatures.
Because tools made of the F-steels (cold drawing dies, for example) are used mainly for applications requiring wear resistance, they are usually placed in service at or near their maximum hardness. Therefore, tempering temperatures higher than 400°F are seldom used. The effects of tempering temperature on hardness for the F1, F2, and F3 steels are shown in the graph, which shows tempering characteristics of carbon-tungsten special-purpose tool steels tempered for two hours after being brine quenched.
Volume 4D, Heat Treating of Irons and Steels -> Tool Steels -> Heat Treating of Cold-Work Tool Steels—Low- and Un-Alloyed Water and Oil Hardening Steels -> Carbon-Tungsten Special-Purpose Tool Steel
Because of their tungsten content, F-steels form hard tungsten carbides.
Continue readingOne Minute Mentor: Atmospheres for Water-Hardening Tool Steel
December 3, 2015 Source:
Excellent results are obtained by austenitizing water-hardening tool steels in a slightly oxidizing atmosphere, as indicated by the data in the graph, obtained in tests on type W2. The graph shows the effect of furnace atmosphere on the surface carbon content of W2 tool steel. Specimens were heated at 790°C (1450°F) for 1 hour, quenched in brine, annealed in lead at 705°C (1300°F), and machined in 0.13 mm (0.005 in.) cuts for analysis.
Oxidizing atmospheres are inexpensive, and are usually produced by controlled direct-firing burners. The light scale that is produced is removed by the vigorous water or brine quench. Endothermic atmospheres also are used, but close control is necessary to match the carbon potential of the atmosphere to the carbon content at the surface.
Volume 4D, Heat Treating of Irons and Steels -> Tool Steels -> Heat Treating of Cold-Work Tool Steels—Low- and Un-Alloyed Water and Oil Hardening Steels -> Water-Hardening Tool Steels
Excellent results are obtained by austenitizing water-hardening tool steels in a slightly oxidizing atmosphere, as indicated by the data in the graph, obtained in tests on type W2.
Continue readingOne Minute Mentor: Austenitizing Water-Hardening Tool Steels
November 30, 2015 Source:
Austenitizing temperatures for water-hardening tool steels normally vary from 1400 to 1550°F. Higher temperatures are sometimes used for special purposes. Hardenability increases as austenitizing temperature increases. The optimum time at austenitizing temperature is from 10 to 30 minutes. Preheating is unusual except for very large tools or those with intricate cross sections.
The graph shows the maximum section thicknesses of three classes of water-hardening tool steels that develop minimum hardness of 60 HRC when oil quenched from various austenitizing temperatures.
It is particularly important to protect shallow-hardening steels against scaling and decarburization. Severe scaling can interfere with heat transfer during quenching and slow the required high rate of cooling. Decarburization will produce a soft surface on any tool steel, but in a deep-hardening steel it can be ground off until the underlying hard high-carbon area is reached. Grinding a shallow-hardening steel will frequently expose the soft core.
Volume 4D, Heat Treating of Irons and Steels -> Tool steels -> Introduction to Heat Treating of Tool Steels -> Water Hardening Tool Steels
Austenitizing temperatures for water-hardening tool steels normally vary from 1400 to 1550°F. Higher temperatures are sometimes used for special purposes.
Continue reading