AISI APT TUBE

GENERAL

Gnee APT steel, known as "silver steel", is a high carbon cold steel that works with excellent value for money in the manufacture of simpler tools and components, but require great hardness. It has a simple heat treatment cycle of being hardenable in water or oil. Of the water-hardenable steels is one that has less deformation.

Chemical composition – C (1.20) • Si (0.25) • Mn (0.30) • Cr (0.20) • W (1.00) • V (0.10)
Supply conditions – A condition of grinding in the annealing state with a maximum hardness of 230 HB.

APPLICATIONS

Applied mainly in spearheads (digging), woodworking tools, guide pins, pin extractors, reamers, strokes, guide pins and measuring instruments. In cutting tools, such as saws, drills, faucets, recorders, etc.

HEAT TREATMENT

Stress relief: In tools of complex shapes, with the removal of heterogeneous material in roughing, sudden change of sections, etc., before hardening in tempering the stress relief treatment should be performed to minimize dimensional variations. The treatment should be done at a temperature of 660 ° C for at least 1 hour for every 25 mm and then cooled in the oven to at least 200 ° C and then calm air.

Tempering: When heating during austenization to perform preheating to ensure temperature uniformity and minimize distortion. Preheat to a temperature of 550 ° C Austenize temperature between 780 – 820 ° C. Heat for 1 hour for every 25 mm thickness and add an additional 1 hour for every 25 mm. For larger sections in cold water or cold sections of thinner oil. Maximum hardness can be reached in the HRC tempering of67.

Tempering: It should be done immediately after tempering when the temperature reaches about 70ºC The tempering temperature should be selected according to the specified hardness. As this steel has no secondary hardening, tempering should be around 200 °C, but never below 180 °C for this use as a guide below the tempering curve. Maintain the tempering temperature for at least 1 hour for every 25 mm thickness. The use of a minimum of 2 hours. Double tempering is recommended for greater dimensional stability.

The cooling of 820ºC. double tempering of 2 hours each.

Nitriding: Steel can be nitrided to increase the wear resistance of surface hardening. However, the nitriding process must be controlled so as not to significantly decrease the hardness of the tool body. Nitriding steel this may or may not result in the formation of white coating. The maximum hardness after nitriding is in the range of 900 – 1000HV.

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