Daniel H. Herring, “The Heat Treat Doctor”® is an active member of the engineering, materials and metallurgical community. His undergraduate work was done at the University of Illinois (1971) and graduate work at the Illinois Institute of Technology (1974). Credentials include a Research Associate Professorship at the Illinois Institute of Technology/Thermal Processing Technology Center and…

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Howard Tring is the owner of Vacuum and Low Pressure Consulting, a company that supplies vacuum pump accessories such as reconditioned inlet traps and exhaust filters and new replacement elements for exhaust filters. Vacuum and Low Pressure Consulting also offers on-site vacuum technology and oil sealed vacuum pump repair training and consulting services, customized to…

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Since oil sealed mechanical vacuum pumps started to be commercially available in the 1920s there have been many companies making this type of pump. The oil flooded rotary piston vacuum pump runs at a slow rotational speed and is a heavy duty design. It has been manufactured for about 85 years.

In the early 1900s these pumps were relatively small at up to 40 cfm capacity. By the late 20s and early 30s the industrial revolution was gaining steam and the manufacturers designed larger capacity pumps to suit new applications. By the 1940s rotary piston vacuum pumps were offered in capacities up to 700 cfm. They are known for the ability to keep on running despite ingesting all sorts of contaminants. Kinney claims to have introduced the world’s first rotary pump in 1904, two years after the company was founded. The Kinney document I have just says rotary pump but I presume it was a rotary vane design as other documents say the rotary piston pump design was introduced in about 1909. In 1926 their popular model was the VSD-8811, later to be the KS-47. Current large models are called the ”KT” series. By Howard Tring

When ASTM standard E 2 was published in 1917, ASTM Committee E-4 on Metallography’s first standard, it described the planimetric method for measuring grain size based upon publications by Zay Jeffries, a founding member of E4; but, E 2 only briefly mentioned the intercept method developed in Germany in an appendix at the end of the standard.

The intercept method suggested by Heyn in 1903 [1] is considerably faster to perform manually which has made it popular, despite the fact that there is no direct mathematical connection between the mean lineal intercept length and G. Both straight lines and circles have been used as templates, plus other shapes. By George Vander Voort

We continue our discussion of ways to improve vacuum performance by understanding how to maximize the operation of our vacuum systems.

Tip #7: Materials Selection for Grids, Baskets & Fixtures. General Design Considerations. To obtain the most cost effective design requires a thorough understanding of the service conditions under which the material will be exposed. Important considerations include: Normal operating (exposure) temperature as well as the maximum (and minimum) usage temperatures; Metallurgical stability over the expected duty/thermal cycle (period, frequency, and rate of heating/cooling); Thermal expansion characteristics; Fabrication (or casting) methods (with respect to development of thermal or chemical gradients in the material). By Dan Herring

Burlington, Ontario (December 7, 2012) – Thanks to continued growth in global business, effective December 7, 2012, the Oakville Furnace Manufacturing Division has moved to a new 14,000 sq. ft. facility in neighboring Burlington, Ontario. The new building will help us to optimize productivity and efficiency as we continue to serve the growing needs of…

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For a number of years I have been encouraging people to re-think the ramp-rates they use for their vacuum brazing cycles.  Many brazing shops using rather high ramp-rates during heating claim that “this is the way we’ve always done it”.  Perhaps it’s time to re-think this. From a metallurgical point of view, too-rapid a heating rate can lead to stresses and strains in the metal assemblies being heated, which can often lead to distortion of parts during their heat-up, and can even lead to parts-failure (I’ve seen this too many times).

I have recommended to a number of brazing shops that they slow down their heating ramp rates (and I’ve seen excellent results), using the following guideline: Heat the parts at the fastest rate that will allow you to bring all the parts (assemblies) up to brazing temperature without the need for any holds (for temperature-equalization) on the way up. by Dan kay

When ASTM standard E 2 was published in 1917, ASTM Committee E-4 on Metallography’s first standard, it described the planimetric method for measuring grain size based upon publications by Zay Jeffries, a founding member of E-4.

Jeffries was a graduate student under the famous Harvard professor, Albert Sauveur. Sauveur published a paper in 1894 where he defined grain structures in terms of the number of grains per square mm at 1X. But, he did not develop details on his method. This method is more tedious to use than the Heyn intercept method because a count of the grains must be made by physically marking the grains as they are counted, when done manually. Experiments were conducted to determine the influence of the number of grains counted per grid application using the Jeffries planimetric procedure of ASTM E 112 with a single test circle of varying size. Results show that this is a viable test method and produced good data down to relatively low count numbers per grid application. Bias was not observed at low counts, only data scatter. By George Vander Voort

The word “eutectic” is one that I use in each of my brazing seminars during our discussions about brazing filler metals (BFMs) as well as metallurgical phase-diagrams, but it is also a word used in describing some of the features of metallurgical-structures within a solidified brazed joint.

The word “eutectic” comes from the Greek word “eutektos” which means “easily melted”. Simply put, a eutectic-composition is an alloy of two or more metals, which, when heated to its melting point (solidus temp.), will completely change from solid to liquid at the same temperature (i.e., isothermally). Technically, theoreticians prefer to define a eutectic-reaction in reverse, proceeding from the molten state to the solid. However, I believe my description will help personnel in the brazing world grasp the general concept more easily. by Dan kay

We continue our discussion of ways to improve vacuum performance by understanding how to maximize the operation of our vacuum systems. Tip #6: Controlling Partial Pressure Additions.

Introducing a partial pressure gas into a vacuum furnace at a pressure in excess of the materials vapor pressure will help avoid significant evaporation or “boiling away” of elemental constituents in the materials being processed. Without this control, surface integrity and in some cases the chemical composition of metal (or filler metal) can be affected. By Dan Herring