Losing Our Tempers

Manufacturers may be missing out on Austempering and Martempering

Commonly defined as the controlled heating and cooling of metals to change their microstructure and mechanical characteristics, such as hardness, ductility, tensile strength and impact resistance, heat treatment is a core phase in many manufacturing processes. It enables engineers to vary the properties of a given material to optimise its design performance and ensure consistent, reliable results. In this country, the top heat treatment technologies tend to be standard hardening, tempering, carburising, induction hardening and annealing processes, whereas in the States, where the industry is valued in excess of $20 billion, isothermal treatments like Austempering and, to a lesser extent, Martempering are much higher on the agenda. So are British design engineers and manufacturers losing out by not embracing these technologies?
 
Heat treatment and metallurgy experts Keighley Laboratories of West Yorkshire offer Austempering of steel and ductile iron, as well as case and through hardening of steel components using Martempering, which is typically followed by a separate, conventional tempering operation. Both are fully predictable, interrupted quenching processes and the company suggests they offer manufacturers cost-saving opportunities for varying the alloy content of metals; in the case of austempered ductile iron (ADI), it enables replacing raw materials like aluminium, reducing the section size of castings, even radically revising component design.
 
Underlining that these are long-established, well-proven techniques, Keighley Labs has offered both specialised processes since the late 70's, early 80's, and helped pioneer the application of ADI in this country, for such components as excavator backhoe attachments and jackhammer mouldings. Particularly in the US, Scandinavia and Germany, ADI has become an accepted alternative for steel or aluminium forgings and castings for heavy truck components, construction and mining parts, railroad track plates, agricultural plough points and lifting arms, rifle parts and automotive gears, crankshafts and piston rings. Meantime, Martempering is used for hardening steel gears and gear trains, lawnmower blades, chainsaw guide bars, high alloy valve plates, hand tools, drive shafts and bearing assemblies.
 
Both Martempering and Austempering are designed to overcome the technical limitations of conventional quenching and tempering, particularly with regard to the development of micro cracks, distortion and dimensional changes.  In conventional processes, the metal is heated to an austenitic state, then quenched in oil or water to produce a crystalline structure called martensite; however, the steep cooling gradient can mean that the surface of the component reaches martensite transformation before the core.

 By controlling cooling severity using interrupted quenching in a bath of molten salt, both Austempering and Martempering allow sufficient time for the surface and core to cool at the same rate, resulting in more uniform transformation and a stronger microstructure.
 
Typically performed on carbon and alloy steel stampings, small steel springs and pressings, powdered metal parts and ductile iron castings, Austempering produces bainite in steel and ausferrite in iron, which usually do not require final tempering. It improves the material's ductility and toughness, produces higher impact and fatigue strength, and increases wear resistance, as well as reducing cracking and minimising distortion, lessening the need for subsequent machining.

 In ADI specifically, it utilises a material that is 10% lighter than steel and produces mechanical properties superior to cast and forged aluminium, higher noise-damping qualities than steel and unique work-hardening properties. This provides opportunities for cutting component costs by using less raw material and for casting components near to finished shape, with a surface highly receptive to painting and plating.

A treatment for through and case hardening of alloy-containing steel and certain carbon steels, Martempering is similar to Austempering except that the parts are slowly cooled through the martensite transformation, without developing the associated high residual stresses. Martempered components are usually then tempered to convert them into a more ductile material, which is why the less misleading name 'marquenching' is often used. Whatever the term, this process prevents cracking and substantially reduces component distortion, which also makes it ideal for treating thin or complex parts that are not suitable for press quenching.

Keighley Laboratories carries out Austempering and Martempering in a computer-controlled salt bath furnace, containing liquid nitrate salt, with quick ramp-up and heating uniformity to ±3˚C ensuring optimum processing results and consistent metallurgical properties. It can quench single or multiple components up to ½ tonne at a time, with Martempering typically carried out at temperatures up to 260˚C and Austempering up to 400˚C. Martempering soaking times tend to be shorter, usually between 20 and 30 minutes, whereas Austempered parts can be soaked for 1, 2, 3 even 4 hours or more, to achieve the required bainitic or ausferritic structure. The company also offers a Carbo-Austempering process for developing a tough, high-carbon bainite case on steel components, demanding exceptional tensile strength and toughness.

 Keighley Labs' technicians can design processing routes for specific components and materials, assist with the chemical analysis of components and, where necessary, help revise material specifications and select appropriate heat treatments to achieve the desired properties. They also have an in-depth understanding of TTT (time, temperature, transformation) diagrams, to determine when transformations begin and end for an individual isothermal heat treatment. The company operates a certificated Quality Management System that complies with BS EN 9100, ISO 9001 and EN 9104 for the heat treating of metals, including Austempering and Martempering, for a wide range of industries that takes in the aerospace sector.

For further information, e-mail: memmott@keighleylabs.co.uk  Refer to page 310

Infoserve365 boosts Camvac's productivity

Increasing profit margins through improved productivity and reduced overheads is imperative for companies operating in any manufacturing sector - especially in today's uncertain economic climate -- but identifying where processes can be honed to meet these objectives requires accurate business intelligence, which can be expensive.

However, there are affordable, flexible data capture systems that interface with existing resource planning systems to provide business managers with key performance indicators and, at the touch of a button, give engineers the detailed reports they need to help drive up Operational Equipment Efficiency (OEE).

One leading engineering company providing cost effective manufacturing intelligence and data analysis is Blackburn-based InfoServe365 Ltd, who installed a bespoke system at one of the world's largest single-site metallisation, in-vacuum coating and lamination companies.

Camvac Limited, a leading UK supplier of liquid packaging, metalised films and laminates for the food, beverage, industrial and conversion markets, needed to improve the OEE of its operation for barrier laminates and single web structures at its plant in Thetford, Norfolk.

Infoserve365 designed and installed a bespoke system for Camvac's laminating machine that interfaces with the machine's original control system PLCs and various ancillary control instruments using standard communications protocols. System operation is straightforward and intuitive and provides automated production analysis records for process improvement and quality control activities.

But the real power of the InfoServe365 system is that the manufacturer can take advantage of real time production analysis reports, journals and trending modules on a range of specific processes and derived from relevant data parameters.

Camvac's management team can now easily access a variety of critical business information such as daily, monthly or weekly downtime events and production analysis, both by day and by shift, from anywhere in the world.

As a result, Camvac has seen significant process improvements and clearer quality control. Manufacturing Director Simon Smith said: "In order for Camvac to maintain it's competitive advantage as a manufacturing 'Best in Class' company, our plant's operational efficiency is crucial to us.

"InfoServe365 provides us with powerful business information from our production plant as soon as it happens. By installing InfoServe365, we have reinforced our commitment to continually improve OEE, ensuring that we always meet our stringent high quality standards and maintain an operational advantage over our competitors."

Infoserve365 joint managing director Michael Hill added: "The advantage of Infoserve365 is that users only need web access to operate the system, there is no need for dedicated server space. With only a few mouse clicks, board members, production managers, process engineers and maintenance engineers all have access to empirical machine data, from wherever they are in the world."

Blackburn-based InfoServe365 is a UK leader in managed data collection and analysis and is the sister company of Optima Control Solutions Ltd (OCS), which has developed an unrivalled reputation for designing, building and commissioning high-quality drive control systems.

Established in 1995, Infoserve365 was the brainchild of Mr. Hill and fellow managing director Dr Adrian West and has grown steadily since then to provide a blue chip service to an impressive client base both here in the UK and overseas, including customers in Europe, China and South Africa.

Optima Control Solutions Ltd is an independent company and industry leading specialist in variable speed drive, PLC and SCADA applications, serving multi-sector manufacturing industries since 1995. For further information, e-mail: Michael.hill@infoserve365.com or view  website: www.infoserve365.com

4-Axis CNC sharpener restores drill bits inexpensively

The US manufacturer, Darex, has introduced a new, 4-axis CNC drill sharpener, designated XPS-16, capable of restoring high-performance drills in a simple, one-touch operation. Distributed in the UK by 1st MTA, Salisbury, the heavy duty unit costs the equivalent of 100 radial split point carbide drills, yet even unskilled operators can sharpen more than 400 of them in a day. Return on investment is typically under eight months.

A wide variety of conical, four facet, split point and radius split point twist drills with angles from 90 to 150 degrees can be processed, including high speed steel, cobalt, solid carbide and coated tools from 51 to 254 mm (2 to 10 inches) long and 3 to 16 mm (1/8 to 5/8 inch) diameter.

In operation, a blunt drill is inserted into the mains-powered sharpener's chuck and the required standard or custom type of drill point is selected using a simple LCD touch screen panel. On initiation of the sharpening cycle, three independent electronic sensors automatically detect the drill's length and diameter, precisely locate the cutting edge and calculate the web thickness.

The unit then sharpens the drill and applies the required split point form in one seamless operation, without operator involvement. It will also hone carbide drill edges as part of the automatic process, extending tool life and maximising drill bit machining accuracy.

The XPS-16 allows user-specific drill sharpening programs to be created easily and stored along with the pre-installed standard programs. It also incorporates Darex's latest 'grind motion control' system, which detects excess material on a blunt drill bit.  This enables the grinding feed rate to be adjusted automatically, both to prevent burning and to provide optimum sharpening performance.

The bench-top sharpener incorporates a vacuum filtration system to eliminate grit and airborne contaminants such as carbide dust.  Its computer control includes advanced diagnostic software that alerts operators to potential problems during the sharpening cycle.

Long-lasting superabrasive plated grinding wheels, 180 grit cubic boron nitride for HSS drills and 220 grit diamond for carbide tools, together with lifetime-lubricated seals, ensure low maintenance and long operational life. Components are modular for easy in-house calibration and service. For further information, view website: www.1mta.com