Michael A. Aronov

Intensive quenching theory and application for imparting high residual surface compressive stresses in pressure vessel components

An alternative method for the hardening of steel parts has been developed as a means of providing steel products with superior mechanical properties through development of high residual compressive stresses on the part surface, and involves the application of intensive quenching during heat treatment. This processing method, termed Intensive Quenching, imparts high residual compressive stresses on the steel surface, thus allowing for the use of lower alloy steels, reduction or elimination of the need for carburization and shot peening, and providing for more cost-effective heat treating. Intensive quenching also provides additional environmental benefits, as the process uses plain water as the quenching media in contrast to traditional heat treatment practices which typically employ hazardous and environmentally unfriendly quenching oil. This paper presents an overview of the theory and application of intensive quenching, as well as provides experimental and computational data obtained for a variety of steel products. Also presented will be results of computer simulations of temperature; structural and stress/strain conditions for a typical pressure vessel during intensive quenching.

One More Discussion “What is Intensive Quenching Process?”

Three intensive quenching processes known as IQ-1, IQ-2, and IQ-3 are considered. In contrast to IQ-2 and IQ-3, processes that use water as a quenchant, the two-step IQ-1 technique is actually a combination of a conventional quench (in oil or polymer/water solution) as the first step, followed by intensive quenching in water (the second step). Similar to the IQ-2 and IQ-3 methods, the IQ-1 process provides residual surface compressive stresses, optimum hardened depth, and additional strengthening (superstrengthening) of the material. A database and a method of calculating the IQ-1 process parameters are considered. The authors underlined that IQ processes are green environmentally friendly methods that significantly reduce CO2 emissions and energy consumption. Also examples of the use of IQ-2 and IQ-3 methods for quenching different kinds of steel parts (such as shafts, pinions, crosses, etc.) are provided. It is shown that the IQ technology’s rapid and uniform cooling rates increase service life of steel parts due to the creation of high residual compressive stresses at the surface of steel parts and due to additional strengthening (superstrengthening) of the material.

Local Film Boiling and Its Impact on Distortion of Spur Gears During Batch Quenching

The paper discusses results of computer simulation connected with the double distortion during batch quenching of spur gears caused by a local film boiling between teeth. A carburized gear, outside diameter 2.5 in., was intensively quenched in conditions that provided heat transfer coefficient (HTC) equal to 25 000 Wm−2K−1. In some places between teeth local film boiling took place where HTC was 800 Wm−2K−1. Computer simulation showed that maximum displacement is observed between teeth where local film boiling took place. The authors came to the conclusion that increasing critical heat flux densities and elimination of local film boiling can result in decreasing distortion of spur gear. That is true for different sizes of gear during their quenching when using the second type of intensive quenching process (IQ-2) technique (a two or three-step quenching process). It is underlined that critical heat flux densities have a great effect on distortion during batch quenching. The authors also came to the conclusion that a small amount of special additives can decrease significantly distortion during quenching of gears. That is why a global database on cooling capacity of quenchants should be available which must contain critical heat flux densities of different kinds of quenchants.

Overview on Super Strengthening Phenomenon Taking Place During Intensive Quenching of Steels

This paper presents an overview on the super strengthening phenomenon that takes place during intensive quenching (IQ) of steels. It is shown that for obtaining an additional strengthening of material, one should pay special attention to whether the part cooling rate within the martensite range is high enough and whether compressive stresses are formed at the surface of steel parts. For hardening high carbon alloy steels with a low martensite start temperature, a two-step quenching procedure is recommended. At the first step of quenching, the martensite transformation is delayed, and, at the second step of quenching, the part cooling rate is accelerated within the martensite range. For hardening low and medium carbon steels, an IQ-3 quench method is recommended when a so-called direct convection cooling is applied for providing a maximal cooling rate within the martensite range and maximal compressive stresses at the surface of steel parts. To calculate a part cooling rate within the martensite range, a generalized equation is provided. Data on mechanical properties for different steels proving a presence of the super strengthening effect are provided also. A practical use of the super strengthening phenomenon is discussed in the paper.

Batch Intensive Quenching Processes for Minimizing Steel Part Distortion and Improving Part Performance Characteristics

This paper discusses an intensive quenching method known as the IQ-2 process. The IQ-2 method is a two- or three-step quenching process for steel parts conducted in highly agitated water. The method is based on the use of a self-regulated thermal process that takes place during the quenching of steel parts in cold liquids such as water or water–salt solution. This quenching method eliminates the film boiling process and provides better control of the martensitic transformation during quenching, resulting in a significant reduction of part distortion after quenching. It also improves material mechanical properties and the performance characteristics of steel parts. It is underlined that proper software and equipment should be used when applying the IQ-2 quenching method for steel parts. Several practical examples of the application of the IQ-2 process are provided.

Intensive Quenching Theory and Application for Imparting High Residual Surface Compressive Stresses in Pressure Vessel Components

An alternative method for the hardening of steel parts has been developed as a means of providing steel products with superior mechanical properties through development of high residual compressive stresses on the part surface, and involves the application of intensive quenching during heat treatment. This processing method, commercially patented under the name IntensiQuench SM , imparts high residual compressive stresses on the steel surface, thus allowing for the use of lower alloy steels, reduction or elimination of the need for carburization and shot peening, and providing for more cost-effective heat treating. Intensive quenching also provides additional environmental benefits, as the process uses plain water as the quenching media in contrast to traditional heat treatment practices which typically employ hazardous and environmentally unfriendly quenching oil. This paper presents an overview of the theory and application of intensive quenching, as well as provides experimental and computational data obtained for a variety of steel products. Also presented will be results of computer simulations of temperature, structural and stress/strain conditions for a typical pressure vessel during intensive quenching.Copyright