Belt types include woven mesh furnace belts of high-grade alloy construction for lighter loaded product types, cast link furnace belts with alloy link pins for heavier loaded product types, slat conveyors for specific gears or other shapes that lend themselves to large contact area style belts, and carrier belts. “Flat-surface” belt furnaces may have cast alloy links, slats or woven mesh, while “broken-surface” belt furnaces have troughs, flights or channels to support and convey work through the furnace.

Belt furnaces are available in the following size ranges: Cast Belt Hardening with widths 24″-72″ and lengths 10′-60′ with production rates of 500-20,000 lbs/hour; Mesh Belt Hardening with widths 24″-66″ and lengths 8′-45′ with production rates of 250-7,500 lbs/hour; Belt Quenching Systems with widths 36″-84″ and production rates of 250-7,500 lbs/hour; and Mesh Belt Tempering with widths 36″-72″ and lengths 10′-50′ with production rates of 250-7,500 lbs/hour. Custom engineered sizes are available.

Belt furnaces can operate at maximum temperatures up to 2200°F. Higher temperature furnaces typically operate at 1400°F to 1950°F using radiant/conduction style heat transfer. Lower temperature styles for tempering or stress relieving operate from 350°F to 1400°F and typically incorporate convection fans.

Belt furnaces can perform annealing, austempering, brazing, carbon restoration, carbonitriding, carburizing, forging, hardening, neutral hardening, normalizing, reheating for press quench, sintering, spheroidizing, stress relieving, tempering, and through hardening. Traditional and boost diffuse carburizing—where zone separation is necessary for different process step temperatures or carbon potentials—can also be performed.

Process atmosphere choices include nitrogen, endothermic (RX®), exothermic (DX®), air, nitrogen/methanol, products of combustion, nitrogen/hydrogen, or dissociated ammonia. Quenchant options include oil, polymer, caustic, and high temperature salt. For products requiring an internal atmosphere, only indirect gas firing and electric heating may be used.

Loads can be charged and discharged by hand, gravity, robotic or other automatic mechanisms. Continuous belts convey work directly through the furnace at a uniform speed with accurate time-cycle control. Work can be bulk loaded or precisely placed for product that requires oriented loading. Racks or baskets can be used for periodic short runs. Gravity, robotic, or automatic loaders are available with vibration and ram-type designs offering a wide range of customization.

Belt furnaces are available with electric, direct gas-fired (recuperative and regenerative), and indirect gas fired (radiant tube) heating systems. For products requiring an internal atmosphere, only indirect gas firing and electric heating may be used.

Cascade quenching is used where small quantities of parts are dropped into the quench at one time. Separation of the oil from the furnace atmosphere is done via oil cascades which create a wall. Typical agitation in these style quenches are via pumps and nozzles pointed at the surface of the belt which retrieves the free falling parts and brings them up to the surface where they may be passed to a washing system prior to tempering. The oil can be heated via electric bayonet style heating elements and is cooled after quenching to return the oil temperature to the setpoint.

Surface’s extensive belt furnace line capabilities include dumpers, washers, tempers, quench tanks, and custom configurations. A typical line can include pre-washers to prepare components for treatment, quench tanks designed to match furnace capacity, draw or tempering furnaces, post-washers to remove residue after quenching, soluble oil systems for rust preventative coating, and loading cars and tables.

Surface offers a full line of process control systems from basic single loop controls to advanced Supervisory Control And Data Acquisition (SCADA) systems. Control systems are fully integrated with equipment safety hardware and PLC systems. Advanced SCADA systems offer recipe database, alarm database, historical trending of all key process parameters, part lot tracking, real-time part tracking through the entire process line, and historical retrieval of part lot processing parameters including temperature, atmosphere, process times, feed rates and any alarm conditions. Controls meeting the requirements of AMS-2750 and CQI-9 can be provided as requested.