NX344 is a special grade which is developed by our Ningshing Special-Steel. It is high quality level of 1.2344 ESR, a kind of hot work tool steel. At the beginning, we develop this grade for making plastic mold for high-grade of snack box because of its better performance on thermal resistance and good toughness that could improve to get a longer lifetime of the mould.
Chemical Composition (%)
Delivery Condition EAF+LF+VD+(ESR), Forged, Spheroidizing Annealed, EFS, Hardness≤230HB, Machined surface, UT 100% SEP1921 Class 3 E/e,
Spheroidized Microstructure as per standard NADCA207-2003 AS1-AS9
Impact test: Transverse impact test as per ASTM A370, V notch impact test (5 samples, size of 10 x 10 mm), average value >=11 J (delete max. and min.), single value >=8 J
Start Forging Temperature
Finish Forging Temperature
Pit or Sand Cooling
Annealing 750 to 800°C (1382 to 1472°F) Slow controlled cooling in furnace at a rate of 10 to 20°C/hr (50 to 68°F/hr) down to approx. 600°C (1112°F), further cooling in air. Hardness after annealing: max. 235 HB.
Stress relieving 600 to 650°C (1112 to 1202°F) Slow cooling in furnace; intended to relieve stresses set up by extensive machining, or in complex shapes. After through heating, hold in neutral atmosphere for 1 - 2 hours.
Hardening 1000 to 1040°C (1832 to 1904°F) Oil, salt bath (500 - 550°C / 932-1022°F), air Holding time after temperature equalization: 15 to 30 minutes. Obtainable hardness: 52 - 56 HRC in oil or salt bath, 50 - 54 HRC in air.
Tempering Slow heating to tempering temperature immediately after hardening / time in furnace 1 hour for each 20 mm of work piece thickness, but at least 2 hours / cooling in air. It is recommended to temper at least twice. A third tempering cycle for the purpose of stress relieving may be advantageous. 1st tempering approx. 30°C (86°F) above maximum secondary hardness. 2nd tempering to desired working hardness. The tempering chart shows average tempered hardness values. 3rd for stress relieving at a temperature 30 - 50°C (86 to 122°F) be low highest tempering temperature.