Search Results for heat treating operation

This article provides an overview of the effects of various material- and process-related parameters on residual stress, distortion control, cracking, and microstructure/property relationships as they relate to various types of failure. It discusses phase transformations that occur during heat treating and describes the metallurgical sources of stress and distortion during heating and cooling. The article summarizes the effect of materials and the quench-process design on distortion and cracking and details the effect of cooling characteristics on residual stress and distortion. It also provides information on the methods of minimizing distortion and tempering. The article concludes with a discussion on the effect of heat treatment processes on microstructure/property-related failures.

This article focuses on induction hardening process for heat treating operations specifically designed to result in proper microstructure/property combinations in either localized or in the final parts. It briefly reviews the heat treating basics for conventional heat treating operations of steels with iron-carbon phase and transformation diagrams. The article provides a summary of the important temperatures, definitions, and microstructural constituents associated with heat-treated steels. Basic transformation characteristics of heat-treated steels are reviewed. The article also discusses the various aspects of steel heat treatment by induction processing, and concludes with a description of steel alloys for induction processing.

Heat treating furnaces require different control systems and integration for achieving optimum technical results and enabling safe operation. This article focuses on atmosphere furnaces, with some coverage on controls for vacuum furnaces. Heat treating operations require reliable monitoring and control of motion and position of various mechanical components with the help of mechanical limit switches, proximity sensors, and distance- and position-measuring devices. Using inputs from both flow meters and sensors, such as thermocouples and oxygen sensors, flow measurement control systems must be able to adjust the flow of gases for process optimization. The operator interface of a furnace-control system displays critical information such as the furnace temperature, atmosphere status, alarms, electronic chart recorders, recipe, and maintenance. A supervisory control and data-acquisition (SCADA) system is used to monitor, collect, and store data from multiple pieces of equipment.

This article describes the methods for removing metallic contaminants, tarnish, and scale resulting from hot-working or heat-treating operations on nickel-, cobalt-, and iron-base heat-resistant alloys. It provides a brief description of applicable finishing and coating processes, including polishing, electroplating, ceramic coatings, diffusion coatings, and shot-peening. The article presents numerous examples that identify cleaning and finishing problems and the procedures used to solve them.

Mathematical models have been used for over five decades in industrial heat-treating operations. Most of these modeling efforts have emanated from academia or research institutes, with the primary approach of mathematically capturing heat-treating processes and validating quality predictions. In this article, a contrarian but more realistic scenario is considered, where two industrial problem descriptions become the starting point. The technical complexity of the industry problem has been elaborated for a deeper understanding of the issue along with elaboration of the approach and potential methods for determining a solution. Then, quantitative analyses of practical industrial problems are demonstrated. Finally, the potential shift in these approaches with the advent of Industry 4.0 is outlined.

This article presents a simple cost/pricing system that is reasonably accurate and could easily be recalculated if the yearly cost of any of the basic cost components change. Using the example of a commercial heat treating facility, the operational details are categorized as atmosphere processes, induction processes, aluminum processes, high-heat processes, and secondary processes. For the purpose of calculating the heat treatment processing cost per hour and the selling price for a piece of equipment, the costs are separated into direct costs, allocated costs, capitalized cost, and general and administrative costs. The article discusses the techniques involved in allocating costs to the group of equipment, and presents a description on the cost analysis of endothermic gas.

Electromagnetic induction is a way to heat electrically conductive materials such as metals. This article provides a brief history of electromagnetic induction and the development of induction heating technology. It explores various applications such as heating prior to metalworking, heat treating, melting, joining (welding, brazing/soldering, and shrink fitting), coating, paint curing, adhesive bonding, and zone refining of semiconductors. The article also discusses the advantages of induction heating.

Batch furnaces and continuous furnaces are commonly used in heat treating. This article provides a detailed account of various heat treating equipment and its furnace types, including salt bath equipment (externally heated, immersed-electrode and submerged-electrode furnaces), and fluidized-bed equipment (external-resistance-heated fluidized beds). It describes various auxiliary equipment used in cold-wall furnaces, namely, heating elements and pumping systems. Five types of heat-resistant alloys are used for furnace parts, trays, and fixtures: Fe-Cr alloys, Fe-Cr-Ni alloys, Fe-Ni-Cr alloys, nickel-base alloys and cobalt-base alloys. The article lists the recommended applications for alloys for parts and fixtures for various types of heat treating furnaces.

Control of temperature and furnace atmospheres has become increasingly critical to successful heat treating. Temperature instrumentation and control systems used in heat treating include temperature sensors, controllers, final control elements, measurement instruments, and set-point programmers. This article describes these items and discusses the classifications and control of furnace atmospheres. The article also describes the surface carbon control devices available for the wide variety of furnace atmospheres and evaluation of carbon control. Finally, the article provides a set of guidelines for safety procedures that are common to all industrial heat treating furnace installations.

This article provides an overview of steel gear heat treating processes and brings out the nuances of the various important heat treating considerations for steel gear applications. The heat treatment processes covered are annealing, carburizing, hardening, low-pressure carburizing, induction hardening, through hardening, and nitriding. In view of the emerging use of mathematical modeling and optimization, a brief overview of its application for process and design optimization is also provided.

The design of a tool-steel part directly affects the susceptibility to shape distortion on heating and cooling. This article provides information on the selection of chemical composition and the effect of composition on size distortion. It explains the various factors considered to control distortion in tools steels, namely, design, initial condition, machining procedure, and heat treatment. Distortion can occur both during and after heat treatment. The article discusses the chief ways to precisely control the extent of distortion by heat treating and auxiliary mechanical methods. Stabilizing treatments, namely, stabilizing by tempering and stabilizing by cold treatment are used to minimize dimensional changes that occur following heat treatment.

The heat treatment of steel involves a number of processes (such as stress relieving, normalizing, annealing etc) to condition the microstructure and obtain desired properties. This article discusses typical heat treating process control procedures for carbon and low-alloy steels, as well as the importance of time, and temperature control in heat treatment. Temperature Uniformity Survey, a testing procedure intended to map variations in temperature throughout the furnace work zone, helps in precise control of temperature. The article focuses on the measuring instruments used to determine gas pressure, vacuum level, gas flow, and gas composition. It focuses on their measuring quenchant characteristics, including bulk temperature, viscosity, composition, and cooling efficiency. The article describes the procedures for detecting variability in the incoming product. It presents, through an example, the general application of design of experiments techniques to locate and tune vital process parameters. The devices used in the control process of mechanical components are also reviewed.

This article provides a detailed discussion on the types of furnace atmospheres required for heat treating. These include generated exothermic-based atmospheres, generated endothermic-based atmospheres, generated exothermic-endothermic-based atmospheres, generated dissociated-ammonia-based atmospheres, industrial gas nitrogen-base atmospheres, argon atmospheres, and hydrogen atmospheres. Atmospheres for backfilling, partial pressure operation, and quenching in vacuum are also discussed. Furnace atmospheres constitute four major groups of safety hazards in heat treating: fire, explosion, toxicity, and asphyxiation. The article reviews the fundamentals of principal gases and vapors. It describes how the evaluation of the atmospheric requirements of heat treating furnaces is influenced by factors such as cost of operation and capital investment.

Annealing is an essential treatment in the fabrication of metal parts and semiproducts. This article discusses the processes involved in annealing, namely, recovery, recrystallization, and grain coarsening. It lists the heat treatment conditions of processed aluminum alloys. It provides information on the types of heat treatment, which include preheating, full anneal, stabilization, and stoving. The article describes the steps involved for achieving the age-hardening effect and the strongest hardening effect in aluminum. The steps to increase the strength of aluminum alloys by extremely fine, dispersed second-phase particles are: solution heat treatment, quenching, and age hardening. Finally, the article also discusses the process parameters of annealing, including the effect of strain, effect of temperature, effect of heating rate, and the effect of alloy elements, and the effect of annealing on anisotropy.

This article provides a brief description of load conditions for single-shot heat treating, vertical scanning, and brazing and soldering. It discusses the various power components used in power supplies. These include capacitors, integrated power module, transformers, and various switching devices, namely, silicon-controlled rectifiers, insulated-gate bipolar transistors, and metal-oxide semiconductor field-effect transistors. The article also provides information on frequency-multiplication harmonic-induction power supplies, namely, push-pull and half-bridge inverters and full-bridge inverters. Series resonant and parallel resonant circuits and their tuning calculations associated with output networks are also discussed. The article describes the frequency range of simultaneous dual-frequency induction heating power supply, and discusses the advantages, applications, and technical background of independently controlled frequency and power (IFP) induction heating power supply. It concludes with a description of the developments in control systems for modern induction power supplies.

This article provides information on the salt baths used for a variety of heat treatments, including heating, quenching, interrupted quenching (austempering and martempering), case hardening, and tempering. It describes two general types of salt bath systems for steel hardening: the first type uses atmosphere austenitizing followed by salt quench and the second type employs austenitizing salt baths with rapid transfer to the quench salt. The article provides a detailed account on the construction, advantages and disadvantages, and limitations of isothermal quenching furnaces, submerged-electrode furnaces, immersed-electrode furnaces, and externally heated furnaces. It discusses the important applications of various furnace designs, including the austempering of ductile iron, the hardening of tool steels, and the isothermal annealing of high-alloy steels.