Heat Treating of Tool Steels – Annealing
ANNEALING
ANNEALING IS AN ASPECT OF HEAT TREATMENT USED TO SOFTEN STEELS AND TO IMPROVE MACHINABILITY, MATERIAL STABILITY & MECHANICAL OR ELECTRICAL PROPERTIES. THIS IS ACCOMPLISHED BY BRINGING THE STEEL TO A SPECIFIED TEMPERATURE ABOVE THE UPPER CRITICAL TEMPERATURE AND HOLDING AT THAT TEMPERATURE FOR A SPECIFIC AMOUNT OF TIME ACCORDING TO THE INSTRUCTIONS FOR THAT GRADE.
ALL TOOL STEELS ARE SPHEROIDIZED ANNEALED (SPHEROIDAL OR GLOBULAR MICROSTRUCTURE) WHICH PRODUCES A FINE GRAIN STRUCTURE. THE FINE GRAIN STRUCTURE ACHIEVED THROUGH THIS ANNEALING PROCESS ALLOWS TOOL STEELS TO EXPERIENCE FORECASTED GROWTH DURING HEAT TREAT. THIS EXPECTED GROWTH IS CRITICAL TO TOOL MAKERS PRODUCING TOOLS AND PARTS OUT OF TOOL STEEL.
TOOL STEELS ARE ANNEALED AT THE MILL DURING INITIAL PRODUCTION TO DIFFERENT BRINELL HARDNESS RANGES (BHN) DEPENDING ON THE SPECIFIC GRADE OF TOOL STEEL; FOR INSTANCE, AN O1 TOOL STEEL WILL BE NEAR 201 BHN IN THE AS-SHIPPED CONDITION, A SUPER HIGH SPEED GRADE SUCH AS PM T15 WILL SHIP NEARER 277 BHN.
TOOL STEELS CAN BE RE-ANNEALED FOLLOWING HARDENING IF THE TOOL MAKER IS NOT PLEASED WITH THE HARDNESS ACHIEVED DURING HEAT TREAT. RE-ANNEALING IS TYPICALLY A 24-HOUR PROCESS.
NOTE: ANNEALING IS SOMETIMES CONFUSED WITH STRESS RELIEVING. STRESS RELIEVING IS A PROCESS ACHIEVED BY HEATING THE MATERIAL TO A TEMPERATURE LESS THAN THE CRITICAL TEMPERATURE AND DOES NOT CHANGE THE HARDNESS LEVEL, ANNEALING IS DONE ABOVE THE CRITICAL TEMPERATURE.
ANNEALING IS AN ASPECT OF HEAT TREATMENT USED TO SOFTEN STEELS AND TO IMPROVE MACHINABILITY, MATERIAL STABILITY & MECHANICAL OR ELECTRICAL PROPERTIES. THIS IS ACCOMPLISHED BY BRINGING THE STEEL TO A SPECIFIED TEMPERATURE ABOVE THE UPPER CRITICAL TEMPERATURE AND HOLDING AT THAT TEMPERATURE FOR A SPECIFIC AMOUNT OF TIME ACCORDING TO THE INSTRUCTIONS FOR THAT GRADE.
ALL TOOL STEELS ARE SPHEROIDIZED ANNEALED (SPHEROIDAL OR GLOBULAR MICROSTRUCTURE) WHICH PRODUCES A FINE GRAIN STRUCTURE. THE FINE GRAIN STRUCTURE ACHIEVED THROUGH THIS ANNEALING PROCESS ALLOWS TOOL STEELS TO EXPERIENCE FORECASTED GROWTH DURING HEAT TREAT. THIS EXPECTED GROWTH IS CRITICAL TO TOOL MAKERS PRODUCING TOOLS AND PARTS OUT OF TOOL STEEL.
TOOL STEELS ARE ANNEALED AT THE MILL DURING INITIAL PRODUCTION TO DIFFERENT BRINELL HARDNESS RANGES (BHN) DEPENDING ON THE SPECIFIC GRADE OF TOOL STEEL; FOR INSTANCE, AN O1 TOOL STEEL WILL BE NEAR 201 BHN IN THE AS-SHIPPED CONDITION, A SUPER HIGH SPEED GRADE SUCH AS PM T15 WILL SHIP NEARER 277 BHN.
TOOL STEELS CAN BE RE-ANNEALED FOLLOWING HARDENING IF THE TOOL MAKER IS NOT PLEASED WITH THE HARDNESS ACHIEVED DURING HEAT TREAT. RE-ANNEALING IS TYPICALLY A 24-HOUR PROCESS.
NOTE: ANNEALING IS SOMETIMES CONFUSED WITH STRESS RELIEVING. STRESS RELIEVING IS A PROCESS ACHIEVED BY HEATING THE MATERIAL TO A TEMPERATURE LESS THAN THE CRITICAL TEMPERATURE AND DOES NOT CHANGE THE HARDNESS LEVEL, ANNEALING IS DONE ABOVE THE CRITICAL TEMPERATURE.
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