Low pressure carburizing (LPC) is a proven, robust case hardening process whose potential is only limited by the style and size of vacuum furnace. Today, LPC is typically used in horizontal vacuum furnaces where the opportunity to carburize large parts is limited. In this paper we present a new adaptation of the technology in large pit type vacuum furnaces, capable of opening to air at elevated temperature. This underscores the potential of LPC to carburize larger, more massive parts in a clean, effective and efficient process. The result is quality casehardened parts without the undesirable side effects of atmosphere gas carburizing such as the use of a flammable atmosphere, reduced CO and NOx emissions, no intergranular oxidation, and limited retort life. Another significant advantage is decreased process time. The case study presented here shows that eliminating furnace conditioning and increasing process temperature can significantly reduce cycle durations by nearly three times and cut utility costs in half. Under these conditions, a return on investment (ROI) is in the neighborhood of 1 – 2 years is possible, making LPC in a pit style furnace a cost-effective solution than traditional atmosphere gas carburizing technologies.

This paper compares and contrasts heat treat processes and equipment typically used to harden gears. It discusses the basic design and operation of vacuum, controlled atmosphere, and hybrid furnaces and process techniques such as carburizing, carbonitriding, nitriding, nitrocarburizing, and neutral hardening. It also includes information on operating and maintenance costs, using batch integral quench furnaces as the base case for comparison. A discussion on when to consider continuous furnace types is included as well.

This paper examines the latest developments in energy management in heat treatment with a specific focus on electrical heating and tighter integration between the power supply and furnace control to maximize energy efficiency. It also discusses the use of IGBT (insulated-gate bipolar transistor) and SCR (silicon-controlled rectifier) based power supplies as energy-efficient alternatives to variable reactance transformers (VRTs) for powering electric vacuum furnaces.

This paper presents four case studies documenting the time and money that heat treaters have saved with the help of predictive maintenance tools. In one case, a heat treater avoided potential catastrophic melting of a heating element and several hangers when predictive maintenance software guided the operator to a broken ceramic in a specific heating zone. In another case, a commercial heat treater was alerted to a low kW reading, indicating a heater failure on a diffusion pump, which would have led to the contamination of a vacuum furnace if not addressed in a timely manner. Situations involving a failing motor on a quench tank and the degradation of furnace insulation are also discussed. Cost comparisons, with and without predictive maintenance, are included in three of the four studies.

This paper discusses the growing use of automation in heat treating and some of the benefits that have been realized in early applications. It provides examples showing how articulated robots are used to load and unload parts on fixtures, how inline 3D cameras facilitate dimensional and distortion control, and how test coupons placed by robots at strategic locations throughout a load are weighed before and after heat treatment to determine if parts in different areas of the load are likely to be carburized to the same degree. It also includes an example of an automatically generated report and explains how binary codes on base trays can be used to automatically upload recipes for specific heat treatments.

This paper presents the results of a study examining the cooling rates of two vacuum high-pressure gas quenching furnaces: a large 10-bar furnace equipped with a 600-hp blower motor and a smaller 10-bar furnace with a 300-hp motor. In comparing critical cooling temperatures for H13 in the 1850°F to 1300°F range, the furnace that is almost three times larger in volume (110 vs. 40 ft 3 of hot zone) cooled the same workload almost identically to smaller unit. The test results clearly show that gas flow, or velocity, is more meaningful than pressure when it comes to cooling rate.

This paper reviews several recent advancements in high pressure gas quenching technology along with the impact of new higher hardenability steels. With design upgrades and improved gas flow and heat removal, a wider variety of materials, part geometries, and load sizes can now be gas quenched.