AISI 4340 Heat Treatment Furnace

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AISI 4140 belongs to ultra-high-strength steel, the implementation standard: ASTM_A29/A29M (forged and cold-worked carbon steel and alloy steel bars).

1. Features and Applications

AISI 4140 has high strength and toughness, good hardenability, no obvious temper brittleness, high alloy steel strength, cutting performance, good resistance, small deformation during heat treatment, and high stress relaxation strength and long-term strength at high temperatures. This steel has excellent process performance, small deformation in production and processing, very good fatigue relief, and good low-temperature impact toughness. Among these steels with cutting performance, the 4140 heat treatment process has good strength and excellent combing structure mechanics, good process performance, and high success rate. The application temperature is 427℃. 4140 has high strength, cutting performance, good resistance, small deformation during heat treatment, high stress relaxation strength and long-term strength at high temperature. The steel is suitable for manufacturing large and medium-sized plastic molds that require certain strength and toughness.

2. AISI4140 Alloy Steel Plate Chemical Composition

Element	C	Si	Mn	P	S	Cr	Mo
Minimum	0.38	0.15	0.75	–	–	0.8	0.15
Max	0.43	0.35	1	0.035	0.04	1.1	0.25

3. Mechanical Properties of AISI4140 Alloy Steel Plate

Grade	Physical Properties
	Compressive Strength(MPa)	Strength of compromise(MPa)	Elongation after breaking(%)	Cross-sectional shrinkage rate (%)	Impulsive digestion and absorption kinetic energy (J)
AISI 4140	≥1080	930	≥12	≥45	≥63

4.Vacuum Annealing

The normalizing temperature of AISI 4140 steel should be between 870℃-900℃. Maintain the proper time to heat the steel thoroughly to complete the transformation from ferrite to austenite. After normalizing, AISI 4140 steel can be vacuum annealed. The annealing temperature should be between 800°C and 850°C, and keep the steel for a proper time to fully heat the steel. Cool slowly in the furnace. This treatment will form a structure suitable for machining. The maximum hardness is 241 HB.

5. Vacuum Quenching

The martensite structure obtained after this kind of heat treatment quenching should be carried out between 840°C and 875°C, and the steel should be fully heated for a proper time. The heat preservation time is 10-15 minutes for every 25mm section, and it should be tempered immediately after oil quenching.

6. Vacuum Temper

Tempering is usually to reduce the stress in the hardening process, but mainly to obtain the required hardness and mechanical properties. The actual tempering temperature will be selected according to the required performance. Carefully heat AISI 4140 to a suitable temperature, usually between 550°C and 700°C, and keep it at this temperature for 2 hours every 25mm scribe, and then cool in air. Tempering between 250°C and 375°C cannot be avoided, because tempering within this range will seriously reduce the impact value, resulting in temper brittleness.

Shanghai Geheng Vacuum Technology Co., Ltd. is a vacuum heat treatment furnace manufacturer with many years of experience in design, manufacturing and production. Mainly produce vacuum heat treatment furnace, vacuum sintering furnace, vacuum brazing furnace, New Energy And Environmental Protection Equipment and other vacuum equipments.Provide customized services, equipment work area can be based on customer output.