The Timken Company recently invested $35 million in a new in-line forging press to improve its products. The press was installed so that the company could use its forged-rolled process, which increases product soundness and results in increased center consolidation in larger cross-sectional sizes than the use of just rolling alone. The challenge of installing this press without disrupting production was also successfully met.
Implement a $35 million project and don’t disrupt production.
That was the challenge The Timken Company confronted when it chose to expand its steelmaking capabilities with the installation of a new in-line forge press. Timken, a manufacturer of high-performance steel and mechanical components, has a good track record of successful implementations, and this project quickly shaped up to become another process innovation for the company.
At Timken’s Faircrest Steel Plant in Canton, Ohio, company engineers designed the bulk of the forge-press equipment to reside in a new building adjacent to the existing rolling mill (Figure 1). However, some of the new equipment – ingot table, cradle and roller table, and portions of the aerial transfer – required installation in the rolling-mill building. In the case of the aerial transfer, Timken designed that equipment to move product back and forth in the two areas.
Employees at the Faircrest facility set about the difficult task of safely installing and commissioning this equipment even as ingots traveled overhead on cranes and across the rolling-mill line. This entailed detailed daily work planning, safety spotters to advise installation teams of approaching hot ingots, and an extensive communication system to inform and direct the work teams when it was necessary to evacuate a specific area.
The team completed the installation and commissioned the equipment on plan and without incident, with careful planning and analysis receiving the most credit for driving success.
Evaluating Industry and Customer Needs
Before implementation could even become a challenge, Timken first needed to carefully evaluate and justify the $35 million forge-press investment. The company learned from customers that they wanted high-quality melt in larger rolled sizes with guaranteed-sound centers. Timken directed that need into its new business development (NBD) process. NBD is a decade-old method used internally to integrate market-needs identification, case development, technical solution development and project implementation.
It didn’t take long to make the decision and add sound-center large bar to its product portfolio. From there, the new-product idea advanced with cross-functional teams reviewing market, customer and technical needs. A technical team then increased efforts to design a machine specification that would consistently meet those needs.
The technical team developed a detailed vendor selection tool to evaluate the entire equipment purchase independently, from technical capability to vendor characteristics. This tool allowed the technical team to remove bias from the vendor selection process and purchase the appropriate forge press.
Undergoing a Thorough Technical Preparation Process
Before the forge-press acquisition, technical expectations from the business case went through a proof-of-concept phase to confirm the anticipated technical capabilities and benefits of the proposed acquisition. This part of the NBD process included targeted finite-element modeling (FEM), physical trials and product evaluation for validation.
Rigorous technical evaluation ensued, engaging a fully cross-functional group of engineers and manufacturing, application development, sales and marketing personnel. Their goal was to transform the observed technical trends from the proof-of-concept phase into predictive relationships and guidelines that then drove the manufacturing of high-quality, large-diameter, forged-rolled bar.
Through a combination of FEM, trials with global suppliers and ultrasonic testing (UT) validation, Timken knew exactly what to expect when processing the first sound-center product off this new 3,000-metric-ton open-die forge press.
Utilizing Advanced Computer Modeling and Simulation
All forging and rolling FEM simulations used the commercial software program DEFORM-3Dto define and control the entire forged-rolled process path. Encompassing the process path and all trial locations required modeling four forge-press designs and two rolling mills.
Simulations generally fell into two categories: targeted design of experiments (DOE) or manufacturing recipe development. The targeted DOE work systematically assessed the impact of key process parameters and identified critical deformation conditions needed to create sound centers. Simultaneously, recipe-development simulations applied those conditions to design and specify forging sequences for real-world trials. Figure 2 shows the favorable dimensional correlation between simulated and actual forged-ingot shape for the first real-world trial, building confidence in model accuracy. The key to the modeling process was to understand the fundamental differences between forging and rolling deformation patterns to help produce a superior product.
Forging and Rolling for Sound Centers, Shape Control
Forging during the forged-rolled process increases soundness due to centerline deformation. Open-die forging deformation occurs with the workpiece stationary between top and bottom forging dies. Deformation penetrates throughout the whole ingot (or bloom) cross section during a forging stroke. This creates increased center consolidation (healing of microporosity) in larger cross-sectional sizes than rolling alone. (See Figure 3 for an example of the cross-section deformation pattern created in an open-die forging process.)
Rolling facilitates final shape control with localized surface deformation. This occurs at a localized region of the bloom/billet/bar where the rolls contact the workpiece. The workpiece moves during the deformation process, limiting the amount of reduction taken per rolling pass while still maintaining workpiece velocity and staying under the rolling-mill load limit. Because of the surface-localized nature of the rolling deformation (Figure 3), Timken optimized the roll-pass sequences to advance dimensional capabilities to more stringent tolerances.
Learning from Global Forging Trials and Validation
Modeling used to develop trial-forging sequences ensured that every trial advanced the company’s knowledge and capabilities and that forged-rolled trial product passed strict UT validation standards. Ultrasonic inspection was the key tool used to calibrate and validate the soundness quality that the advanced modeling tools predicted.
Figure 4 shows an actual UT scan (blue lines) of forged-rolled product successfully adhering to a strict ultrasonic specification (no indications above the red and green line limits). Figure 5 shows a summary of UT results measured for forged-rolled and rolled-only process paths at various bar sizes. The results indicate that conformance to a UT standard significantly improves with the introduction of the forged-rolled process.
The combination of empirical trials with UT results provided the data required to transform the simulation models into predictive optimization tools. Timken utilized the recipes developed through modeling and trial evaluations as seeds for press start-up. Manufacturing operators took those recipes and further optimized them for efficiency in the Faircrest Steel Plant work stream, applying the key guidelines from the modeling and trial efforts to achieve center soundness and final shape requirements.
Improving Dependability and Performance
The new forged-rolled process gives Timken an expanded product range, enhances productivity and quality and increases capacity. For customers, the proven cleanliness and enhanced sound centers in larger bar sizes translate into improved dependability and performance of their critical components in applications worldwide.
As the world continues to push the limits, industries continue to explore ways to get more out of their product performance and optimize operations. Enter Timken steel. Timken has supplied large forged-rolled products to its industry-leading customers, offering them the opportunity to create better and larger products to improve productivity and performance.
The forged-rolled process delivers product with the best of both worlds. With targeted deformation at the forge press and precision sizing from the rolling mill, the forged-rolled process creates larger bar sizes capable of meeting stringent soundness requirements and allows Timken large bar sizes to lead the industry in soundness and size control.