1.2714 JIS SKT4 AISI L6 Die Block Steels

1.2714 JIS SKT4 AISI L6 Die Block Steels

1 1.2714 Introduction:

1.2714 L6 Low alloy special purpose steels or group L steels contain small quantities of chromium, nickel, vanadium, and molybdenum. L2 and L6 form the group L steels. The L6 Die Block Steels contain 0.70% carbon with a quenched hardness of about 64 HRC. The alloying elements in these Die Block Steels are chromium and molybdenum, and 1.50% nickel to increase toughness. These Die Block Steel can maintain hardness above 60 HRC for sections of 75 mm (3 in.) thickness.

2 1.2714 Applications:

Typically used in machine tool applications such as bearings, springs, rollers or chuck parts.

3 Quality Standard:

ASTM A681 Standard Specification for Tool Steel

4 All Grades Comparison:

5 1.2714 Chemical Composition(%):

6 HEAT TREATMENT:

FORGING: L6 Die Block Steels are forged at 1079°C (1975°F) down to 871°C (1600°F). These steels should not be forged below 843°C (1550°F).

ANNEALING: Annealing must be performed after hot working and before re-hardening.
Heat at a rate not exceeding 400°F per hour (222°C per hour) to 1400°F (760°C), and hold at temperature for 1 hour per inch (25.4mm) of maximum thickness; 2 hours minimum. Then cool slowly with the furnace at a rate not exceeding 50°F per hour (28°C per hour) to 1000°F (538°C). Continue cooling to ambient temperature in the furnace or in air. The resultant hardness should be a maximum of 235 HBW.
For improved machinability, hold at 1400°F (760°C) for1 hour per inch (25.4mm) of maximum thickness; 2 hours minimum. Then cool slowly with the furnace cool from 1400°F (760°C) to 1250°F (677°C), hold for 8 hours, then air cool to ambient temperature. The resultant hardness should be a maximum of 192 HBW.

HARDENING: L6 Die Block Steels should be preheated at 1200°F, soaked, then raised to a hardening temperature of 1500 to 1550°F and held for one hour per inch of greatest cross section. Quench in oil to a temperature of 1500°F, followed immediately by tempering. Tools made of L6 Die Block Steels in sections less than 1 in. thickness are often air-quenched from 1500°F. Air quenching provides safer hardening of intricate sections. It also results in less distortion than oil quenching.

TEMPERING: L6 Die Block Steels should be tempered at 400°F. However, where increased toughness is desired, at a sacrifice of some hardness, higher tempering temperatures are often used.
L6 Die Block Steels do not become brittle, as many other die steels do, when tempered in the range of 450 to 800°F. A minimum holding time of one hour per inch of thickness should be used when tempering at 400°F.
To minimize the possibility of cracking, the steel should be tempered immediately after hardening and should be heated slowly to the desired tempering temperature.
For the tempering test of this grade, specimens 7/8 in. round by 2-1/2 in. long were hardened from 1500°F in air-blast furnace and from 1525°F in oil. The hardened specimens were tempered at temperatures ranging from 300 to 1000°F at 100-degree intervals.

7 Mechanical Properties:

8 Mill′s test certificate:

EN 10204/3.1 with all relevant data reg. chem. composition, mech. properties and results of testing.