Search Results for blanket cylinders

The thermal spray community serves the printing industry with a variety of protective coatings applied on behalf of original equipment makers and end users. This article describes the applications of thermal spray coating for printing equipment such as engraver rolls, plate and blanket cylinders, corona rolls, and draw rolls.

Spray quenching refers to a wide variety of quenching processes that involve heat removal facilitated by the impingement of a quenchant medium on a hot metal surface. This article provides information on the basic concepts of spray quenching, and discusses the most commonly used techniques in quench tank agitation to establish uniformity of the quenched part. Common techniques include quenchant stirring, quenchant circulation, and submerged jet/spray mixing. The article also describes the effect of quenching agitation and reviews heat-transfer characteristics of immersion quenching and spray quenching with water.

This article details investigations on the characterization of various nanofluids as quenchants for industrial heat treatment. It provides a discussion on the preparation, stability, thermophysical properties, and wetting characteristics of nanofluids. The article explains the mechanism of heat transfer in nanofluids and discusses the effect of the deposition of nanoparticles on the probe surface. The article also presents the microstructure and mechanical properties of steel quenched in nanofluids.

Spray quenching (or jet impingement) is the most common technique employed to improve the uniformity of heat removal and break the vapor layer, allowing for a high cooling rate to be achieved. This article presents the heat transfer characteristics of quenching a hot surface, which can be expressed by the boiling and quench curve. It discusses three major spray parameters that have a substantial role in the quantification of spray cooling performance: droplet size, droplet velocity, and volumetric flux. The article also presents the available models and correlations to predict the cooling rate in spray quenching of hot surfaces during different boiling phases. It then discusses the effect of surface roughness on spray cooling performance.

This article presents the modes of heat transfer and the stages of cooling during quenching. It provides an overview on the wetting process and then focuses on the evaluation of heat transfer during quenching. It also presents the challenges of thermal process evaluation based on an inverse heat conduction analysis. The article contains a compilation of best practice examples on heat transfer evaluation, which are intended to represent the practical aspects and applicability of the methods aiming the prediction of heat-transfer coefficients.

Inverse hardening a steel of adequate hardenability requires a workpiece of sufficiently large cross section, an appropriate cooling medium, and the right quenching conditions. This article explains the Temperature Gradient Quenching Analysis System (TGQAS), which can measure, record, and evaluate all quenching processes in common use, describing their heat extraction dynamics by corresponding thermodynamic functions. It discusses the metallurgical aspects of steels with an emphasis on two different processes, namely, heat extraction (a thermodynamic process) and microstructural transformation (a metallurgical process) that are initiated at the moment when the austenitized workpiece is immersed in the quenchant. The article describes the uses of polyalkylene glycol copolymer and the effect of hardness and fatigue resistance on AISI 4140 type steel.

This article presents the fundamentals of induction hardening (IH). It focuses on liquid quenching technology, but some specifics and brief comments are provided regarding alternative quenching media as well. The article provides a discussion on the following quench modes that can be applied in IH using liquid media: conventional immersion quenching, open spray quenching, flood quenching, and submerged quench or submerged spray quench. It also focuses on four primary methods of IH: scan hardening, progressive hardening, single-shot hardening, and static hardening.

This article provides information on the various stages of quenching, sources of distortion, and factors that affect the creation of thermal gradients. It reviews the various determinations of heat-transfer coefficients by the thermal conductivity and diffusivity method, analytical and empirical methods, application of cooling curves, computational fluid dynamics, and the inverse conduction calculation and measurement of parts. Suitable examples are also provided.

Intensive quenching (IQ) is an alternative method of hardening steel parts, providing extremely high cooling rates within the martensite-phase formation temperature range. This article begins with the description on the general correlation between steel mechanical properties and cooling rate during IQ. It presents a review of batch intensive quenching (IQ-2) methods and single-part intensive quenching (IQ-3) methods as well as practical applications of these methods. The article provides useful information on the effect of heat flow on cooling in these methods, and discusses the improvements achieved in part microstructure, mechanical properties, and stress conditions of steel, after intensive quenching. It also describes the reasons for part distortion in IQ, and reviews the types of quench systems used in IQ-2 and IQ-3 processes.

In this article, a metallurgical overview of the hardening process is provided. This overview is followed by the methodology involved in obtaining cooling curves, the currently accepted standardized methods of testing, and the use of newer methods of cooling curve data interpretation that describe the quenching process.

Estimation of process parameters for selective heating and heat treating of simple- and complex-shaped workpieces in induction hardening can be accurately carried out using numerical simulation techniques such as the finite-element analysis and the finite-different method. Along with the significant benefits of modern numerical simulations, it is important to be able to use rough estimation techniques to develop a general understanding of the critical parameters of a particular induction heating system. This article discusses such numerical techniques for estimating the critical parameters: workpiece power estimation; estimation of electrical and thermal efficiency of the coil; and frequency selection for heating solid cylinders, tubes, pipes, slabs, plates, strips, and rectangular workpieces.

Submerged arc welding (SAW) is suited for applications involving long, continuous welds. This article describes the operating principle, application, advantages, limitations, power source, equipment, and fluxes in SAW. It reviews three different types of electrodes manufactured for SAW: solid, cored, and strip. The article highlights the factors to be considered for controlling the welding process, including fit-up of work, travel speed, and flux depth. It also evaluates the defects that occur in SAW: lack of fusion, slag entrapment, solidification cracking, and hydrogen cracking. Finally, the article provides information on the safety measures to be followed in this process.

This article describes the mechanisms and characteristics of heat transfer in the quenching of steel. This article describes the characterization of boiling heat transfer, including pool boiling, forced convective boiling, and rewetting, which plays a key role in defining the heat-extraction characteristics of a liquid quenchant. It provides information on heat generated microstructural field evolution and information on the analysis and characterization of heat transfer boundary conditions.

This article provides a discussion on probes for laboratory tests and resultant curves of industrial quenching processes. It describes the scope of the tests, and the calculation of heat-transfer coefficient (HTC) based on the tests. The article highlights the differences between the laboratory tests and characterization of industrial quenching processes. It reviews the importance of initial heat-flux density and first critical heat-flux density. The theoretical principle behind and the purpose of the temperature gradient method are discussed. The article provides information on the design of the probe, heat-extraction dynamics, and influence of wetting kinematics. It also includes discussions on the simplified 1-D temperature-distribution model, calculation of the HTC, and the finite-volume method for the heat-conduction equation.

This article provides an overview of common quenching media, the factors involved in the mechanism of quenching, and process variables, namely, surface condition, mass and section size of the workpiece, and flow rate of the quenching liquid. It describes the methods of quenchant characterization using hardening-power and cooling-power tests. The article discusses the fundamentals involved in heat-transfer coefficient and heat flux of quenching processes. This discussion is followed by various actual examples of applications of these methods using simplified equations. Quenchant evaluation, classification, selection, and maintenance are reviewed in detail. The article addresses the various reasons for quench oil variability and complications due to aging and contamination.

Intensive quenching (IQ) is an alternative method of hardening steel parts. Two types of IQ methods are used in heat treating practice: IQ-2 and IQ-3. IQ-2 is implemented in IQ water tanks, which are usually used for batch quenching of steel parts. IQ-3 is conducted in single-part processing using high-velocity water flow IQ units. This article presents a detailed description of IQ technology, related equipment, and IQ applications. A review of intensive quench system design and processing is provided, including numerical design criteria, steel selection, quenchants, properties (especially optimal residual stress profiles). Several specific applications of intensive quenching are also provided.

High-temperature exposure of materials occurs in many applications such as power plants (coal, oil, natural gas, and nuclear), land-based gas turbine and diesel engines, gas turbine engines for aircraft, marine gas turbine engines for shipboard use, waste incineration, high-temperature fuel cells, and missile components. This article discusses high-temperature corrosion in boilers, diesel engines, gas turbines, and waste incinerators. Boilers are affected by stress rupture failures, waterside corrosion failures, fireside corrosion failures, and environmental cracking failures. Contamination of combustion fuel in diesel engines can cause high-temperature corrosion. Gas turbine engines are affected by hot corrosion. Refractory-lined incinerators and alloy-lined incinerators are discussed. The article provides case studies for each component failure.

Induction heating for hardening of steels has advantages from the standpoint of quenching because parts are individually processed in a controlled manner. This article provides information on the effect of agitation, temperature, hardening, residual stresses, and quenching media, on quenching. It also describes various quenching methods for steel induction heat treating, namely, spray quenching, immersion quenching, self or mass quenching, and forced air quenching. The article also reviews quench system design and quenchants and their maintenance.

The use of gases or molten salts as the quenchant for steel parts is commonly limited to the quenching of high-alloy steel or the carbonizing quenching of low-alloy steel. This article reviews the quenching process of steels with molten metals (quenchant) such as molten lead, molten bismuth, and molten sodium. It also contains tables that list the physical properties of lead, bismuth, sodium, and molten sodium.