New Developments in Heat Treating Equipment for the Fastener Manufacturing Industry

The Heat Treating of high volume, mass produced high integrity threaded fasteners has been an environment where market demands for product quality standards, delivery and costs have grown exponentially over the last decade. Adages or expressions like “Lighter–Stronger-Faster”, “Value Added Services” and “Doing More For Less” are all common within the walls of high-volume Fastener Manufacturing Facilities. These pressures have forced manufactures to seek out new and creative methods for improving their competitive position. One area where there has been significant improvements made and new developments commercialized is with the systems used to heat treat these often “safety critical” threaded fasteners.

Background

The methods for heat treating threaded fasteners have evolved significantly over the years. Ferrous threaded fasteners were once processed in systems that included small capacity shaker hearth and rotary retort systems. As production capacity and size range flexibility became more important, manufacturers gravitated towards high capacity Continuous Belt Style Furnaces. Today these same manufacturers routinely choose Continuous Mesh Belt Heat Treating Systems for the many benefits they offer. In addition to ferrous fasteners we would be remiss if we did not touch on non-ferrous (aluminum) fastener processing, whose volumes have continued to grow as a result of new automotive powertrain and magnesium component developments. Their exacting quality and volume requirements were traditionally well managed using straight forward batch heat treatment systems. However, because of the continued growth in automotive applications these aluminum fasteners are now more commonly processed using higher volume continuous belt heat treatment systems. Given the processes used to heat treat vary widely between ferrous and non-ferrous (aluminum) fasteners this paper will focus on the new heat treatment system developments associated with the processing of ferrous fasteners.

Today’s Environment

Today most high volume manufacturers of fasteners utilize fully integrated continuous heat treatment systems. These systems are highly automated systems requiring minimal operator involvement following the bulk loading of dunnage containers to the entry of the system. CAN-ENG Furnaces International has led in the movement to further improve these heat treating systems in an effort to not only meet the quality standards required by customers but to also improve upon their operating efficiency, which in turn improves their competitive advantage.

Improvements in Manufacturing Processes

Reducing Part Damage during Processing

As part of CAN-ENG’s continuous improvement initiatives, CAN-ENG has focused on integrating mesh belt conveying technology utilizing a wire woven belt for each individual customer’s needs and process requirements. The integration of CAN-ENG’s “SOFT HANDLING” systems and part transition know-how have significantly reduced part nicking that would in most cases require re-threading of fasteners. In addition, fasteners are loaded externally to the austenitizing and tempering furnaces. This reduces the empty gaps deposited on the belt for proper lot separation improving the operating efficiency of the system.

Increasing Heating Efficiency and Reducing NOx Levels

Improvements in natural gas heating systems include the integration of newly developed self-recuperated burners that provide similar heating efficiency to that of the high cost regenerative burners. Environmentally, these new regenerative burners when coupled with a newly designed radiant heating tube can reduce the NOx levels by 50% over that of conventional recuperative burners.

Waste Heat Recovery

Further improvements in protective atmosphere consumption and waste heat recovery has been a focus for CAN-ENG. Much like the natural gas CAN-ENG uses to heat furnaces CAN-ENG also utilizes natural gas to manufacture the endothermic gas to protect the fasteners from decarburization. Recently, CAN-ENG has developed and integrated its Energy Reduction System (ERS) to include an atmosphere reduction system which reduces endothermic gas requirements by 40% and a waste heat recovery system which reduces overall natural gas consumption by 15% compared to conventional systems.

Dephosphating Enhancements

CAN-ENG has improved upon the options available to fastener manufacturers when dephosphating is required. This has been accomplished through the he in-line integration of mesh belt dephosphating equipment with the heat treatment system. This new developed option eliminates the need for off-line rotary systems currently in use by most manufactures today.

Hybrid Quenching System

Today’s fastener manufacturing environment requires operational flexibility to be capable of providing a wide variety of cost effective fastener configurations and grades. In some cases, this flexibility dictates that the manufacturer integrate the use of many material grades or chemistries that require different heat treatment processes to achieve the desired mechanical properties. These properties can be significantly altered through the use of different quenching methods including Hot Oil, Polymer, Water and Molten Salt. Can-Eng has developed a method that allows processors the opportunity to alternate quenching mediums to suit the product being processed. This flexible concept allows users the benefit of reduced equipment requirements while having the flexibility to process a full range of fasteners.

Control System Integration

Developments in area of process controls has been a significant area of improvement for CAN-ENG. The integration of a Level 2 SCADA systems into its manufacturing processes enables manufacturers to monitor, control and update in real time. Functions like basic time temperature data acquisition capabilities, off-site process monitoring and control, system diagnostics, inventory control, preventative maintenance and system efficiency tracking can be included in a SCADA system resulting in significant gains in quality, inputs and outputs.

CAN-ENG’s Continuous Mesh Belt Furnace Systems have earned an international reputation for the following: