A.B. Chattopadhyay

Beneficial effects of cryogenic cooling over dry and wet machining on tool wear and surface finish in turning AISI 1060 steel

Abstract High production machining of steel inherently generate high cutting temperature, which not only reduces tool life but also impairs the product quality. Conventional cutting fluids are ineffective in controlling the high cutting temperature and rapid tool wear. Further, they also deteriorate the working environment and lead to general environmental pollution. Attempts have already been initiated to control the pollution problem by cryogenic cooling which helps also in getting rid of recycling and disposal of conventional fluids. The present work deals with experimental investigation in the role of cryogenic cooling by liquid nitrogen jet on tool wear and surface finish in plain turning of AISI 1060 steel at industrial speed-feed combination by two types of carbide inserts of different geometric configurations. The results have been compared with dry machining and machining with soluble oil as coolant. The results of the present work indicate substantial benefit of cryogenic cooling on tool life and surface finish. This may be attributed to mainly reduction in cutting zone temperature and favorable change in the chip–tool interaction. Further, it was evident that machining with soluble oil cooling failed to provide any significant improvement in tool life, rather surface finish deteriorated.

The influence of cryogenic cooling on tool wear, dimensional accuracy and surface finish in turning AISI 1040 and E4340C steels

Abstract In all machining operations, tool wear is a natural phenomenon and it eventually leads to tool failure. The growing demands for high productivity of machining need use of high cutting velocity and feed rate. Such machining inherently produces high cutting temperature, which not only reduces tool life but also impairs the product quality particularly when the work piece is quite strong, hard and heat resistant. Conventional cooling methods are not only ineffective but also deteriorate the working environment by producing harmful gasses and smokes. Attempts have already been initiated to control the pollution problem by cryogenic cooling which also enables get rid of recycling and disposal of conventional fluids and possible damage of the machine parts by corrosion, etc. This paper deals with experimental investigation on the role of cryogenic cooling by liquid nitrogen jet on tool wear and product quality in plain turning of AISI 1040 and E4340C steel at industrial speed–feed combinations by two types of carbide inserts of different geometry. The encouraging results include significant reduction in tool wear rate, dimensional inaccuracy and surface roughness by cryogenic cooling application mainly through reduction in the cutting zone temperature and favourable change in the chip–tool and work–tool interaction.

Effects of cryogenic cooling by liquid nitrogen jet on forces, temperature and surface residual stresses in grinding steels

Grinding is a widely employed finishing process for different materials such as metals, ceramics, glass, carbides, rocks, etc. to achieve good geometrical (form) and dimensional accuracy with acceptable surface finish and surface integrity. However, it is inherently characterized by high specific energy requirements, unlike other conventional machining processes such as turning, milling, etc., which lead to a high grinding zone temperature and poor surface integrity. Many methods have been investigated to control this high grinding zone temperature, but all have their shortfalls, both technological and environmental, in exchange for controlling the grinding zone temperature. This paper briefly discusses the results obtained with regard to grinding forces, specific energy, grinding zone temperature and surface residual stress when using cryogenic cooling and compares them to the results from dry grinding and grinding with soluble oil. Cryogenic cooling seems to have the edge over other coolants in terms of controlling the temperature, residual stresses and grinding forces, and it is also environment friendly.

The effect of cryogenic cooling on grinding forces

Grinding forces are important parameters to judge the performance of any grinding process. Cryogenic cooling in grinding is a new concept to control the high grinding zone temperature without polluting the environment. The paper presents a hypothesis on the mechanics of grinding under cryogenic cooling. Experiments have been carried out to study the effect of cryogenic cooling on grinding forces and to check the validity of the hypothesis. The results indicate substantial reduction in the grinding forces under cryogenic cooling over range of infeed and dressing procedure for different commonly used steels.

Role of Cryogenic Cooling on Cutting Temperature in Turning Steel

Application of conventional cutting fluids do not serve the purposes effectively particularly under high cutting velocity and feed. Besides, such cutting fluids pollute the environment in high production machining and grinding. Cryogenic cooling seemed to be quite effective in reducing the high cutting temperature which impairs product quality and reduces tool life. The present work deals with investigating the role of cryogenic cooling by liquid nitrogen jet on cutting temperature in turning plain carbon steel (C-40) under varying cutting velocity and feed. The experimental and computational results indicate that such cryogenic cooling enables substantial reduction in the cutting temperature depending upon the levels of the cutting velocity and feed and the cutting tool geometry. It was also noted that the chip formation and chip-tool interaction become more favorable and the cutting forces decreased to some extent when liquid nitrogen jet was employed. Therefore, it appears that cryogenic cooling, if properly employed, not only provides environment friendliness but can also improve the machinability characteristics.

Machining of AISI 4140 steel under cryogenic cooling—tool wear, surface roughness and dimensional deviation

Abstract Increase in cutting velocity and feed for machining with high productivity is generally restricted by the elevated cutting temperature which causes rapid tool failure. In precision machining also, the major problem is the high cutting temperature, which impairs the dimensional and form accuracy of the product, its surface integrity by inducing tensile residual stresses and surface and subsurface cracks. Application of conventional cutting fluid often cannot control the high cutting temperature in high production machining. Besides, they are the major source of pollution from machining industries. Cryogenic cooling is an environment friendly clean technology for desirable control of cutting temperature. The present work investigates the role of cryogenic cooling by liquid nitrogen jet on average chip–tool interface temperature, tool wear, dimensional accuracy and surface finish in turning AISI 4140 steel under industrial speed–feed conditions.

A study of effects of cryo-cooling in grinding

Abstract Grinding yields high temperature which not only limits the wheel life but also induces tensile residual stresses, micro-cracks, etc. at the ground surfaces. This problem becomes acute when the components are of hard and strong materials and used in dynamic loading. In such cases intensive cooling is essential. In this work various steel specimens have been surface ground under dry conditions, with soluble oil and by a liquid nitrogen jet. Significant improvements in the chip formation and reduction in specific energy requirement, grinding temperature and residual stress were observed in cryo-grinding when compared with grinding dry and with soluble oil.

Effects of cryo-cooling in grinding steels

Abstract The grinding process is inherently characterised by high specific energy and high temperature, which are responsible for high wheel loading, increased grinding forces, reduced metal-removal rate, rapid wheel wear and deterioration in the quality of the ground surface through oxidation, the induction of tensile residual stress and micro-cracks. These problems become more acute when the product is of HSHR material and subjected to dynamic loading while functioning. Therefore, in industry the user should pay special attention to control and optimise all the significant parameters for minimising the afore-said problems, aiming at higher grindability, productivity and overall economy in grinding. The basic principles of controlling such high temperature are: (i) proper selection and optimisation of wheel and process parameters; (ii) the removal of heat from the grinding zone by the application of proper grinding fluid. Profuse cooling with conventional grinding fluids, even in the form of mist or jet, is virtually unable to solve the problem. However, cryogenic cooling by agents such as liquid nitrogen is expected to meet this challenge. In the present work, specimens of different steels, namely MS, HCS, cold- and hot-die steel and HSS, have been surface ground at different infeeds under dry conditions and with soluble oil and liquid nitrogen. The effects of such cryo-cooling relative to soluble oil and dry grinding have been investigated in respect of chip formation, grinding forces, specific energy, burning and surface characterisation. The experimental results indicate that the grinding temperature and burning decreased remarkably under cryo-cooling. Thermal damage of the ground surface has been reduced substantially by cryo-cooling, but to different degree in different steels. Cryo-cooling also enables retention of the wheel sharpness for a longer period and results in less force and specific energy being required.

Determination and control of grinding zone temperature under cryogenic cooling

Abstract Grinding processes, though employed widely as a finishing process, have their own share of problems, like high grinding zone temperature which may lead to thermal damage to the work surface, like induction of tensile residual stresses, development of microcracks, enhanced risks of wheel loading and excessive wheel wear. Grinding fluids are applied in different forms to control such high temperature, but they are partially effective within a narrow working range; recent studies also indicate their polluting nature. cryogenic cooling, if employed properly, could control the grinding zone temperature more effectively by intensive removal of heat from the grinding zone. The present study deals with the effect of cryogenic cooling on grinding zone temperature for five commonly used steels both experimentally and computationally. Results indicate that the effectiveness of cryogenic cooling is substantial throughout the experimental domain.

Development and performance of zirconia-toughened alumina ceramic tools

Abstract Modern ceramic tools with their remarkable improvements in properties and versatile performance are gradually replacing carbide and coated carbide tools, particularly in the area of machining carbon steel, cast iron and heat-resistant alloy. Ceramic tools will be of more interest to the manufacturers and users of the countries such as India where there is scarcity of tungsten and cobalt. However, the ceramic tools need to be tough and versatile to suit the wide range of power and rigidity of the machine tools. The present authors have tried to develop some tough ceramic inserts mainly based on alumina and zirconia which are readily available in India. Characterization and performance of these tools in machining low and medium carbon steels have been studied. Some of the tools with suitable geometries have been successful in machining at speeds up to 450 m min −1 .