Title

IMPROVEMENT OF THE SAE 1080 CARBON STEEL HARDNESS RANGE FOR GRANITE SAW APPLICATION USING THE SIX SIGMA METHODOLOGY

IMPROVEMENT OF THE SAE 1080 CARBON STEEL HARDNESS RANGE FOR GRANITE SAW APPLICATION USING THE SIX SIGMA METHODOLOGY

Authorship

Toledo Jr, Francisco Geraldo

Toledo Jr, Francisco Geraldo

I am this author

DOI

10.5151/2594-5297-40064

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Abstract

THE SAE 1080 STEEL, CONTAINS 0.79% TO 0.82% OF CARBON, HAS GREATER MECHANICAL RESISTANCE AND LOWER DUCTILITY COMPARED TO LOW AND MEDIUM CARBON STEELS. IT IS A FLAT STEEL CLASSIFIED AS HIGH CARBON AND HAS A PREDOMINANTLY PEARLITIC MICROSTRUCTURE. SOME POSSIBLE APPLICATIONS OF THIS STEEL ARE: MARBLE AND GRANITE SAWS, BAND SAWS, CIRCULAR SAWS, HANDSAWS, AMONG OTHERS. THE COST OF CUSTOMER COMPLAINTS FOR THIS TYPE OF PRODUCT TENDS TO BE RELEVANT. IN DECEMBER 2017, SAE 1080 STEEL PRODUCTION BEGAN, INTENDED FOR APPLICATION IN GRANITE SAWS. THE SAWS USED IN THE LOOMS ARE TAKEN DIRECTLY FROM THE SHEETS OF HOT-ROLLED COILS WITHOUT THE USE OF ANY SUBSEQUENT HEAT TREATMENT, BEING MOUNTED ON LOOMS THAT VARY BETWEEN 80 AND 140 BLADES. THE VARIATION IN THE MICROSTRUCTURE IS A CRITICAL ISSUE THAT ALTERS THE HARDNESS OF THE BLADES, WHICH CAN CAUSE BREAKAGE (IN CASE OF HIGH HARDNESS) OR SEVERE WEAR (IN CASE OF LOW HARDNESS). USING THE SIX-SIGMA METHODOLOGY, VARIABLES THAT CAN INFLUENCE THE VARIATION OF THE MICROSTRUCTURE AND, AS A CONSEQUENCE, THE VARIATION OF HARDNESS OF HOT-ROLLED SAE 1080 STEEL WERE ANALYZED. AFTER THE ANALYSIS AND IMPLEMENTATION OF ACTIONS, IT OPTIMIZED THE LENGTH OF THE SLABS IN THE MELT SHOP AND THE COILING TEMPERATURE IN THE HOT ROLLING MILL TO OPTIMAL RANGES, MEETING THE CUSTOMER'S SAE 1080 HARDNESS REQUIREMENTS IN THIS APPLICATION

The SAE 1080 steel, contains 0.79% to 0.82% of carbon, has greater mechanical resistance and lower ductility compared to low and medium carbon steels. It is a flat steel classified as high carbon and has a predominantly pearlitic microstructure. Some possible applications of this steel are: marble and granite saws, band saws, circular saws, handsaws, among others. The cost of customer complaints for this type of product tends to be relevant. In December 2017, SAE 1080 steel production began, intended for application in granite saws. The saws used in the looms are taken directly from the sheets of hot-rolled coils without the use of any subsequent heat treatment, being mounted on looms that vary between 80 and 140 blades. The variation in the microstructure is a critical issue that alters the hardness of the blades, which can cause breakage (in case of high hardness) or severe wear (in case of low hardness). Using the six-sigma methodology, variables that can influence the variation of the microstructure and, as a consequence, the variation of hardness of hot-rolled SAE 1080 steel were analyzed. After the analysis and implementation of actions, it optimized the length of the slabs in the melt shop and the coiling temperature in the hot rolling mill to optimal ranges, meeting the customer's SAE 1080 hardness requirements in this application

Keywords

Granite saws; Hardness; Microstructure

Granite saws; Hardness; Microstructure