China is already the largest manufacturing country in the world, boasting the highest production and sales of steel, main nonferrous metals and engineering machines. By 2045 the world’s most populous country aims to not only be the largest, but also the undisputed leader of all the strong manufacturing countries, part of the recently conceived ‘Made in China 2025’ plan. For the manufacturing industry, this means a drive towards advanced, innovative, intelligent, energy saving and sustainable industry.
Professor Zhang Chenhui, speaking at F+L Week 2018 in Macao, says the rapid development of industries related to metalworking is having considerable influence on the policy and consumption of metalworking lubricants in the region. While this offers the opportunity to grow metalworking fluid (MWF) demand, there is also a higher requirement for efficiency, accuracy and improved surface quality, plus more environmentally friendly.
Zhang received a PhD from Tsinghua University, in Beijing, in 2004, and has considerable experience in water-based lubrication, super lubricity and surface coating technology. He is a previous winner of the National Science Foundation for Outstanding Young Scholars (2013) and has published 60 Science Citation Index (SCI) papers in Langmuir, Soft Matter and Applied Surface Sciences.
The global consumption of MWF in 2017 is expected to touch 2.5 million tonnes. China is already the preeminent consumer of metal processing lubricants and is enjoying astonishing annual growth rates of 7% to 20%. However, Zhang caveats that in China, and many parts of Asia, consumers continue to adopt mineral-based lubricants due to price sensitivity. He predicts synthetic-based fluids will witness significant growth in the region on account of their superior capabilities, such as increasing tool life and excellent surface finish.
The machining (35%) and automotive (35%) industries are the major users of MWF in China — with metalware a distant third (12%). Within individual metal machining processes, cutting and forming are the leading patrons with a combined share of 74% of all MWFs, followed by protection (13%) and treatment processes (8%).
Growth in industries that rely on metalworking fluids in China is propelling demand for lubricants. “With higher demand, comes a greater performance requirement,” says Zhang. The Tsinghua University professor outlined several performance trends during his presentation, which include the requirement for MWFs to become more multi- functional; increasingly customizeable; more environmentally friendly; new lubrication methods; and individual lubricant requirements for different metals.
Zhang emphasized that the development of metalworking processes is placing a higher requirement on base oils, additives and water-based lubricants — forcing MWFs to be more multi-purpose to meet the diverse needs of customers. Consumer expectations include cooling, lubrication, cleaning, anti-rust, stability, antibacterial and green properties.
Despite a trend to multifunctional MWFs, or a “one-size-fits-all” approach, a movement towards individually customized MWFs according to the process requirements of the customer is also prevalent, he confirms.
The strengthening of environmental laws and regulations, and enhanced consumer awareness of environ- mental protection — is gaining traction. Zhang suggests that more and more chemical substances are being banned, generating a greater need for safer, healthier, more environmentally friendly and biostable technology. Common ecological problems in MWFs include red tides, water biohazards, water pollution, and safety and health problems such as skin irritation, respiratory irritations and explosion.
Zhang highlighted a range of individual lubricant technology requirements for the different types of metalworking processes.
While he concedes there are a lot of types of forming, generally the focus should be on removability, lubricity and viscosity in what is typically a high pressure, high-temperature environment. The friction in metal forming processing is in a mixed state of dry friction, liquid friction and boundary friction. Insufficient lubrication can cause plate type and surface defects.
In rolling applications, there is a trend to high speed, better surface quality, wide width, smaller thickness, large reduction and surface tension control after rolling. Zhang stresses that these requirements necessitate a high-quality rolling fluid. For the base oil, low viscosity is necessary to minimize film thickness; it must have low sulphur and low aromatics content, a high flash point and narrow boiling range. Additive requirements include high lubricating property, economical efficiency and stable performance. In cases where water-based lubricants are acceptable — they should be eco-friendly, with sufficient lubricating property, and corrosion issues need to be alleviated, outlines Zhang.
The relative movement between workpiece and tool during cutting removes excess metal and achieves the desired shape and accuracy. For cutting, appropriate lubrication is vital to reduce cutting temperature, improve surface quality, jettison cutting chips, enhance tool service life and improve machining precision. Zhang says the base oil must possess enough viscosity to form EHL (elasto hydrodynamic lubrication) film and dissolve the additives. Additives should easily be able to penetrate the cutting area and provide lubricating properties and anti-wear protection.
Aluminium and magnesium alloys are increasingly popular due to their light weight and ability to save energy. Machining fluids for these types of non-ferrous alloys need to solve key problems such as hard water stability and corrosion of non-ferrous metals, confirms Zhang. Difficult to manufacture metals such as titanium alloys, cobalt-based alloys and nickel-base alloys are often used in aerospace, shipbuilding and medical applications. In this instance cutting fluids must provide improved surface quality and superior lubrication, to minimize the ‘serious’ wear of tooling. Appropriate fluids also promote higher machining speeds and improve efficiency.
The light weight and high strength properties of composite materials are also gaining in prevalence. The most widely adopted engineering structural materials are fiber-reinforced composite materials such as glass fiber reinforced composite (GFRP), car- bon fiber reinforced composite (CFRP), aramid fiber reinforced composite (KFRP) and boron fiber reinforced composites, says Zhang. Composites are used widely in rail transportation, ships and energy applications. Compound material’s technical requirements include tool wear resistance and thermal conductivity, improved surface quality and dust pollution reduction.
Finally, Zhang described a shift to micro-lubrication technology, also known as minimum quantity lubrication (MQL) in China. This approach has many advantages
— including a smaller volume of lubricant, reduced maintenance of cutting fluids, lower cost, environmental benefits and energy savings, and it can be more conducive to chip evacuation. Consequently, the process is becoming increasingly adopted by companies, though Zhang warns that the technical requirements for lubrication are much higher to ensure better lubricity, extreme pressure performance and faster oil film formation rates.