The distortion behavior of carburized and fully heat treated Ni-Cr-Mo martensitic steel (S156) has been experimentally evaluated. Dimensional measurements of Navy C-ring distortion coupons during interrupted heat treatment process for parts manufactured from two forming routes, hot forging and machined from as received bar, was performed. Metallurgical analysis was carried out to attempt to relate the observed microstructural characteristics with measured process induced distortion. The carburization process was found to be the most severe in terms of inducing distortion. It was found that additional heat treatments during the process results in a larger final distortion. Machining parts from forgings results in higher distortions than that of those machined directly from as received bar due to the added thermal processing history. A finite element simulation of the carburization process for a C-ring coupon is presented.

Modern technological advancements make it easier to achieve accurate control to meet AMS2750E and CQI9. Today’s Industrial technologies have advanced rapidly alongside electronic innovations that improve accuracy and control. In years past, there was a certain difficulty associated with accuracy from older existing controls to new modern process controls due to the level of complexity and cost involved. Today, equipment manufacturers are integrating a variety of new technology to improve accuracy for more accurate monitoring. This paper looks at some of the old and new technology innovations for input accuracy regarding both analog and digital signals.

In the design of a downhole isolation tool for multi-stage fracturing in the oil and gas industry, a setting component, called slip, was used to set the tool in the casing prior to the hydraulic fracturing operation. The material of the slip is made of gray cast iron with surface hardening requirement. This study investigated the performance of slips treated by induction hardening versus flame hardening. The slip treated by induction hardening produced low hardness and insufficient affected layer. On the other hand, flame hardening generated satisfactory results of case hardening layer by 0.762 mm (0.030 in.) thickness with 50 HRC minimum hardness. The Type E graphite in the raw material was transformed to Type A in the flame hardening process, which is favored in the case hardened layer. The effect of different treatment processes on the affected layer and their microstructural response in gray cast iron was discussed in this study. The isolation tool using the slip treated by flame hardening, together with other proven components, showed successful performance of 82.7 MPa (12 ksi) pressure holding at 177 °C (350 °F) for high pressure and high temperature downhole applications.

Achieving appropriate temperature uniformity in a heat treat application with direct fired burners requires paying particular attention to burner type, spacing and arrangement. Selection of the appropriate burner technology is crucial for achieving required uniformity. This paper explains the importance of proper burner placement (spacing and arrangement) and will describe advancements in burner technologies that provide important options to achieve required temperature uniformity. The paper concludes with several short case studies explaining the application of spacing, arrangement and technology to achieve the proper temperature uniformity in the furnace. These case studies are relevant to thermal processing of titanium, steel, and aluminum components.

Quench hardening is a transient thermal stress process with phase transformations. It is inevitable that a component will go through plastic deformation due to phase transformations, which will lead to distortion in the hardened part. Understanding the sources of distortion is necessary in designing the heat treat process and component configuration to obtain a product with greater dimensional accuracy. It is worth mentioning that consistent distortion can be compensated by adjusting the part dimensions prior to hardening. The possible sources of distortion include residual stresses prior to hardening, heating rate, austenitizing temperature, soaking time, quenching rate and uniformity, and possible tooling constraints, etc. The significance of these effects varies according to the part geometry and heat treatment process. Characterization of material properties and the development of computer modeling made it possible to understand the material and component responses during quench hardening, which is the key to process improvement and part configuration optimization. In this paper, the hardening process of a simplified bevel gear with thin-wall feature made of AISI 9310 is analyzed using DANTE, and the effect of tooling used in a press quench on distortion is investigated. The causes of distortion are analyzed through the material response aspect using the modeling results.

Test pieces are often used for hardened depth and microstructure checks on carburize and harden heat treatment processes so that actual parts are not destroyed for the sake of quality assurance. For gear heat treatment, this is especially important because of costly prior processing. This paper reports on a study to determine the proper size and material of a cylindrical test piece that could be used as an appropriate indicator of the hardened depth and microstructure of the actual gear. Heat treat simulation is used to examine cooling rates for various diameters of test pieces to see how they compare to different modules of tooth sizes on gears. The surface cooling rates up to depths of 1.5 mm are examined to size the test piece correctly.

The purpose of this presentation is to outline challenges faced by the Heat Treat Industry related to momentary short circuits when electrical furnaces are used in the production process. The common causes of the problem will be outlined along with some examples of the types of equipment and processes that are impacted by these phenomena. The heat control loop, focusing specifically the power control and semiconductor protection will be analyzed and discussed. Newly developed technologies to overcome these issues and the benefits of such technologies will also be discussed. Some common causes of SCR Power control failures and technologies related to integrated thermal protection and diagnostics, and how these technologies are in line with Industry 4.0 will also be presented.

The use of nitriding to improve a component’s resistance to wear, fatigue, and corrosion continues to increase across the industry. However, for nitrided components, no universally accepted definition of “case depth” is available to allow the comparison of different nitriding processes, cycles, and materials. This study documents currently published methods of specifying and determining case depth for nitrided components, and evaluates the reported case depth of multiple materials and cycles in an effort to determine an optimal and robust “universal” method of reporting case depth. After completing this exercise, it appears that the optimal “universal” method of specifying and reporting the case depth for a nitrided component is to report the depth at which a Vickers microhardness traverse crosses a threshold which is 50HV greater than the material hardness below the nitrided case.

This paper describes a study to address sustainability by improving the power density of induction-coupled thermo-magnetic processing treatment of low-cost steel alloys. Application of a 9Tesla magnetic field in heat-treating improved the performance of the low-cost steels to rival that of exotic, costly alloys in properties and performance.

Induction heating is very sensitive to part geometry. How mass is distributed in a part can have a strong influence on how it heats and the case depth that can be achieved. One application where this has been observed is in the internal hardening of connecting rod journals. These parts have an uneven distribution of mass that causes a cold-sink effect due to the position of the rod on one side of the bore. Computer simulations of the heating and cooling processes show how the mass imbalance affects the temperature in different areas of the workpiece, and they yield insights into how the temperature history of the different areas influences the resultant microstructure after hardening. The phenomena observed may be applicable to any part having a feature to be hardened with uneven mass distribution around the feature, and principles discussed herein can aid in design of such parts for induction heat treating.

In the recent years, there has been a remarkable increase in the use of deep cryogenic treatment (DCT) for enhancing performance of tool steels. It is a supplementary treatment where components are treated below subzero temperatures for several cryo-soaking hours. This paper focuses on to study the effect of deep cryogenic treatment and cryo-soaking time on microstructural and mechanical properties of AISI H-13 tool steel. Deep cryogenic treatment at different cryo-soaking time (16-48 hours) were applied and tool steel performance was analyzed by using mechanical, fatigue and wear testings. The microstructural evolutions during DCT were evaluated by using scanning electron microscope (SEM). It was observed that microstructural modifications like increase in carbide density, fine and uniform martensitic structure during DCT had significantly improved properties which were influenced by cryo-soaking time.

The potential for improving mechanical properties of steels via thermal processing (e.g. austenization and rapid quenching) through modified phase equilibria in the presence of a high magnetic field has been the subject of numerous recent works [1,2]. In this study, torsional fatigue performance of case-carburized SAE 8620 re-austenitized and quenched inside of a 9 Tesla, 5” diameter superconducting magnet is reviewed. Conventional atmosphere furnace carburized hardened and tempered, and in-situ magnetic field re-hardened and tempered material (Induction Thermo-Magnetic Processing, or “ITMP”) was subjected to fully-reversed torsional loading. Both Special Bar Quality (SBQ) bar and forged SBQ bar steel in carburized conditions were heat treated and mechanically tested. There was no measurable difference in fatigue behavior for either condition when comparing conventionally heat-treated and ITMP re-hardened populations.

Eddy current is a non-destructive testing technique proven for use in heat treat and material structure verification. Modern multi-frequency eddy current instruments can test for conditions such as misplaced case, shallow case, short heat, short quench, and delayed quench. Eddy current testing offers many benefits over traditional heat treat validation methods. Unlike sample testing processes using cut, polish, etch, and visual inspection techniques, eddy current testing provides a clean, fast, and repeatable process that can perform in-line inspections of all parts produced. Eddy current inspections have traditionally focused on symmetrical parts such as wheel bearings and gears. However, advances in robotics have paved the way for cost-effective inspection of non-symmetrical, complex components that would have previously required multiple test stations. Robotics also provides a low-cost way to retest, null, and periodically proof the testing process using multiple conditions of masters. This has been difficult and expensive with other types of automation and operator involvement.

Freight truck shipping is a massive industry and an important contributor to the US economy. Truck axle shafts for decades have been made from induction hardened carbon steel with 0.4% to 0.5% carbon. Associated metallurgical engineering of steel procurements, forging, processing, and applied machining, impacts axle shaft production and performance. This paper reviews metallurgical principles and controls currently applied to heavy truck axle shaft use and production in North America. Basic metallurgical engineering principles and controls, as historically and currently applied and specified, plus potential opportunities for increasing engineering value optimization, are reviewed. In particular, case depth, surface hardness, microstructure, grain size, chemical compositional interactions, procurement, processing, metallurgical evaluation, and overall engineering characterization and achievement targets are discussed.

Heat treatment comprises a series of operations involving heating, holding, and cooling of materials in the solid state for the purpose of obtaining certain desirable metallurgical, mechanical, or physical properties. The driving forces behind developing new heat treatment technologies are reducing the overall process time, minimizing its environmental footprint, minimizing distortion, lowering material cost, and lowering the cost of furnace operations. This paper discusses ten global trends that are driving technology development in the heat treating industry.

An attempt was made to characterize microstructure, mechanical properties and cleanliness of continuous cast as rolled billets versus microstructure, mechanical properties and cleanliness of the forging in normalized condition, upset forged from AISI 41B30 modified chemistry billets. Two forgings were compared, one in as forged condition and one in normalized or heat treated condition. Upsets were produced by upsetting only one end of the billet by hydraulic press. Samples from cold portion of the forgings, near the flange location and from flanges were taken and examined. Results of microstructure, mechanical properties and hardness are presented. Normalizing cycle did not improve mechanical and impact properties. Low impact and ductile properties are results of Widmanstätten structure and continue to be present in the final product. Low impact and ductile properties of this structure might not be the best solution for dynamically loaded parts.

Energy Savings through Steady State Control Modern heat treat companies are faced with challenges trying to balance work-flow, processing time, and production/energy costs. Unnecessarily long processing times induce extra costs when an automated process cannot tell the true temperature of a load and the engineer must increase soak times to accommodate. These increased soak times use more energy and increase overall production costs. Typically, control or load thermocouples in an oven or furnace only show the wall temperature, and normally only parts of the load. However, the real interest is in what temperature the load actually has reached inside and when is the temperature uniform throughout the whole work piece. Normally, to accommodate for this lack of knowledge in a ramp/soak program, the dwell-time is extended to ensure that the temperature is uniform without truly knowing. Instead, using a method for predicting load uniformity, or Steady State Control, would save time, energy, and, most importantly, money.

Austempering is an alternative hardening process that has been operating under the radar of manufacturers and designers for decades, primarily because its application is directed to fasteners having a cross-section of 12.7 mm or less. The primary goal of austempering is to create an extremely tough microstructure throughout the part’s mass or cross-section, a typical requirement for fasteners. This paper provides an overview of austempering processes and applications.

A precipitation hardenable semi-austenitic stainless steel AISI 632 grade was austenitized according to industrial specifications and thereafter subjected to isothermal treatment at sub-zero Celsius temperatures. During treatment, austenite transformed to martensite. The isothermal austenite-to-martensite transformation was monitored in situ by magnetometry and data was used to sketch a TTT diagram for transformation. As an alternative treatment, after austenitization the material was immersed in boiling nitrogen and up-quenched to room temperature by immersion in water prior to be subjected to isothermal treatment. Magnetometry showed that the additional thermal step in boiling nitrogen yields a minor increment of the fraction of martensite, but has a noteworthy accelerating effect on the transformation kinetics, which more pronounced when the isothermal holding is performed at a higher temperature. Data is interpreted in terms of instantaneous nucleation of martensite during cooling followed by time dependent growth during isothermal holding.

Industrial processes require significant amounts of energy to transform raw materials into finished products. Understanding industrial processes, equipment, and support systems is key to finding energy-efficient solutions. This paper covers the basics of sustainable energy efficiency for industrial systems and outlines approaches and programs to help heat treaters reduce energy usage.