One 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.
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One Minute Mentor: Relation Between Tempering Temperature and Hardness
January 8, 2016
Source:
The graphs show the relation between tempering temperature and hardness for D2 and D3 tool steels. Steels were austenitized in an air furnace; a recirculating pit-type furnace was used for tempering. The curves represent steel from three suppliers. An average of five hardness measurements were made on each specimen from each supplier. Specimens were 25 mm (1 in.) in diameter and 38 mm (1.5 in.) long.
It can be seen that certain steels exhibit higher hardness after being tempered at about 540°C (1000 °F) than after being tempered at temperatures 55 to 110°C (100 to 200°F) lower. This reversal in the usual relationship is known as secondary hardening and is caused by transformation of retained austenite and the precipitation of fine alloying carbides during tempering at the higher temperatures, near 540 °C (1000 °F).
Volume 4D, Heat Treating of Irons and Steels -> Tool Steels -> Heat Treating of Cold-Work Tool Steels -> Medium-Alloy Air-Hardening, High-Carbon High-Chromium and High-Vanadium-Powder Metallurgy Steels -> Recommended Heat Treating Practices
The graphs show the relation between tempering temperature and hardness for D2 and D3 tool steels.
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One Minute Mentor: Austenitizing Powder Metallurgy Steels
December 17, 2015
Source:
Steels of groups A and D as well as 8%Cr or High-V-PM steels are usually austenitized in vacuum furnaces or in various types of furnaces using gaseous atmospheres.
Whereas for conventionally produced cold-work tool steels the adjustment of the working hardness is usually done by a combination of different austenitizing and tempering temperatures, PM steels are typically tempered in a small tempering range, from about 550 to 560°C (1020 to 1040°F) with a variation in austenitizing temperature to adjust the hardness level , as shown in the graph.
This different procedure is explained by the toughness results, which increase when austenizing temperature is reduced. Furthermore, because of high content of fine dispersed stable carbides, grain growth at high temperatures does not take place in these steels. Typical austenitizing temperatures therefore range from 1000 to 1180°C (1830 to 2160°F).
Volume 4D, Heat Treating of Irons and Steels -> Tool Steels -> Heat Treating of Cold-Work Tool Steels—Medium-Alloy Air-Hardening, High-Carbon High-Chromium and High-Vanadium-Powder Metallurgy Steels -> Recommended Heat Treating Practices
Steels of groups A and D as well as 8%Cr or High-V-PM steels are usually austenitized in vacuum furnaces or in various types of furnaces using gaseous atmospheres.
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One 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.
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Expo sells out for Heat Treat
September 17, 2015
Source: ASM International
The ASM Heat Treating Society announced that the exposition for Heat Treat 2015 has sold out for the second time in a row. Hundreds of heat treating companies and gear manufacturers will be displaying their latest and greatest products and services next month at the 28th annual ASM Heat Treating Society Conference and Exposition in Detroit, Michigan.
With over 290 booths on the sold out floor – an increase of over 20 booths from 2013 – attendees will have plenty of opportunities to see the latest technology in action. A new addition this year are scheduled live demonstrations on the expo floor, which will educate attendees about new equipment in a hands-on way. Other exciting events happening on the show floor are plenary talk from Dr. Alan Taub of the LIFT consortium on Tuesday afternoon, and the exhibitor reception on Tuesday evening. Exhibitors are encouraged to invite their clients and prospects to attend, particularly if they are local.
Heat Treat 2015 is a biannual conference recognized by industry, academia and government professionals as the premier heat treating gathering in North America. This year it is taking placing in Detroit Michigan, a place with deep roots in heat treating and the birthplace of the ASM Heat Treat Society.
To see a list of the exhibitors, visit this page.
To register for Heat Treat 2015, visit here on the Heat Treat event website.
