SKD61 Tool Steel

SKD61 Tool Steel Heat treatment process

1.Annealing

Purpose: to eliminate internal stresses generated during forging or rolling, reduce hardness, improve cutting performance, and prepare for subsequent processing and heat treatment.
Process parameters:
Heating temperature: 800-850 ℃, holding time 2-4 hours, with the furnace cooling to below 500 ℃, and then air-cooled.
Hardness after annealing: ≤ 235HBS.

2.Quenching

Purpose: to make the steel to obtain martensitic organization, improve hardness and wear resistance.
Process parameters:
Heating temperature: 1000-1050 ℃ (commonly used 1020-1040 ℃), holding time according to the size of the workpiece to determine, generally 30-60 minutes.
Cooling: oil cooling or air cooling (for small size or simple shape of the workpiece), large workpieces can be graded quenching (in the 260-300 ℃ salt bath cooling for a period of time and then air-cooled), in order to reduce the quenching stress, to prevent deformation and cracking.

3.Tempering

purpose: to eliminate quenching stress, adjust the hardness and toughness, stable organization and size.
Process parameters:
low-temperature tempering: 150-250 ℃, insulation 2-3 hours, air-cooled, tempered hardness of 58-62HRC, for molds requiring high hardness and wear resistance.
Medium temperature tempering: 300-500 ℃, insulation 2-3 hours, air-cooled, tempered hardness of 50-58HRC, can improve the toughness, suitable for molds subject to impact load.
High-temperature tempering: 500 ℃ or more, insulation 2-3 hours, air-cooled, tempered hardness 45-50HRC, mainly for the need for higher toughness of the occasion.

4. Precautions

heating process should control the rate of heating to avoid too rapid a rise in temperature leading to workpiece surface oxidation and decarburization. Protective atmosphere heating can be used or placed in the furnace charcoal and other anti-decarburization agent.
When quenching and cooling, choose the appropriate cooling medium and cooling method according to the shape and size of the workpiece to ensure the quenching effect while reducing the risk of deformation and cracking.
Tempering must be sufficient to ensure the elimination of internal stresses to avoid mold failure due to stress release during use. For large molds or workpieces with complex shapes, multiple tempering can be used.

SKD61 Steel Quality Inspection

1. Surface condition inspection

FCS factory has a very strict quality inspection team, we will carefully check the surface condition of each SKD61 STEEL round steel and plate, to ensure that the surface of the steel is free from defects such as cracks, folding, scars, oxidized skin, pitting, scratches and so on.

2. Chemical Composition Testing

To verify that the content of alloying elements meets the standard requirements and to safeguard the basis of the mechanical properties of the material. We will let the staff use full-spectrum direct reading spectrometer to analyze multiple elements at the same time. Sampling needs to remove the surface oxidation layer, using a block specimen to stimulate the test.

3.Dimension and Tolerance Inspection

FCS factory will use professional measuring tools to inspect the dimensions and tolerances of the steel to ensure compliance with the customer's contract requirements. Corresponding gauges will be selected according to the dimensional accuracy requirements, including tape measure, high-precision vernier calipers (0.02mm), micrometers (0.001mm), and special inspection gauges. Inspection items cover: diameter, thickness, width, length, hole diameter, chamfering dimensions, etc., to ensure that the tolerances and dimensions meet the contract requirements.

4.Hardness test

Our FCS factory will use a professional hardness tester to test the hardness of steel to ensure that it meets the customer's contract requirements.

5.Ultrasonic Testing

Ultrasonic Testing Standard (UT Test Standard) is: Sep 1921-84 Class3 D/d,E/e.
FCS factory uses ultrasonic testing equipment to detect macro defects inside the material (such as cracks, shrinkage holes, inclusions, white spots, etc.), and every piece of round steel and plate will be examined by a second flaw detection test before shipment to ensure that the quality is qualified before shipment.

6.Microstructure Inspection

(1) Metallographic Analysis

FCS factory will use metallographic analysis instrument to inspect the microstructure state after heat treatment, including carbide distribution, martensite morphology, residual austenite content, etc.

(2)Grain size rating

FCS factory will use the comparative method to determine the austenite grain size by comparing the microstructure of the specimen with the standard rating chart, to ensure that it meets the customer's requirements.