Long Products Rolling Technologies
High-strength rebar allows for a reduction in bar diameters, resulting in less congestion in the rebar/concrete column and lower overall fabrication costs. This work presents a development for high-strength, 20-mm diameter coiled rebar by properly adding microalloying elements, primarily Nb. Adjustments were made to the thermomechanical industrial rolling schedule to optimize the Nb precipitation effect on austenite during rolling and to use any potential remaining solute Nb for further precipitation strengthening during cooling. A combination of laboratory investigation and metallurgical modeling coupled with industry trials resulted in yield strength and elongation in excess of 600 MPa and 15%, respectively.
This paper presents a thorough review of the literature on defects in beam blanks, focusing on formation mechanism and the solutions proposed to decrease their occurrence. The review includes the techniques used to investigate the defects. The measures taken have to do with changes in liquid steel preparation, in the casting system, mold design, secondary cooling modifications and regulation, strand support, machine alignment, and more.
Surface quality is critical in high-end steel products, such as special bar quality (SBQ) rods and bars. With the introduction and the maturing of imaging-based surface inspection technology, the surface quality information of the product being rolled is provided to long product hot rolling mills in real time. Historically, surface inspection of material produced was done visually by those working on the production line once the product has cooled down, or off-line through processing units using non-destructive testing equipment. The instant visual feedback capability offered by the imaging-based surface inspection technology is leading mills to a shift in operation paradigm. This paper focuses on the utilization and application of the in-line inspection data. Mill examples are used to showcase the use of data during the course of quality and efficiency enhancement in resolving those process control variables that contribute to surface quality defects in the rolling train, as well as in mill management and customer relationship.
The forming characteristics of the electric resistance welding (ERW) tube manufacturing processes will be analyzed in detail. Two typical ERW tube forming processes with and without a cage forming section are compared to make high-strength steel tube and pipe for various applications. The technical challenges during tube forming are presented, such as eliminating the strip edge buckles when making thin-walled tube and reducing the flat spot on the tube surface for improving tube quality. The mill setup and optimizing tooling design, as well as key parameters to check at the mill, are proposed. This paper describes the fundamental tube deformation, which is essential to clearly understand the forming process for achieving better performance of ERW tube mills.
United States Steel Corporation (U. S. Steel) decided to upgrade Gary Works’ No. 1 caster to improve reliability and slab quality. Strategically, the revamp also allowed more challenging steel grades to be shifted from other U. S. Steel casters to Gary Works’ No. 1 caster. This casting machine began operations in 1967 and has since cast more than 68 million short tons of steel slabs. Some upgrades have occurred over the years, but this upgrade represents the second time that a significant overhaul of the caster has been undertaken. The current revamp consisted of adding width-dependent air-mist cooling and split rolls to existing equipment in the upper portion of the machine and installing new carrier frames, removal rails, and 3-roll segments in the bender and bow section of the machine. U. S. Steel also realigned the caster, installed a new bearing cooling water system, main hydraulic system, runout equipment, and also upgraded the tundish level control and crane control. Commissioning of the caster by U. S. Steel and SMS group occurred at the end of 2015. Since the end of the commissioning in February 2016, internal and surface quality has been excellent for all existing and new steel grades, per extensive sulfur printing and visual inspection. Details of the new equipment and quality performance will be reviewed in this paper.
This paper is the recipient of the 2018 AIST Charles H. Herty Jr. Award. For more information about AIST awards, visit AIST.org.
Over the last eight years, significant automation enhancements were made at ArcelorMittal’s Burns Harbor Steel Producing shop for the three basic oxygen furnace (BOF) vessels, the secondary processing stations and the two slab casters. These automation improvements have led to increased production by 6% and a shop yield increase from 86% to 91%. Working ratio during this time period increased from 69.3% to 77.9%. Quality improvements from automation include improving plate rejects by 53.1% and reducing plate reprocessing 23.1%. Overall cost per ton has decreased by 27.6%. Most importantly, the automation changes have decreased the U.S. Occupational Safety and Health Administration injury rate from 0.84% to 0.45% and the all-injury rate from 7.22 to 4.57.