51CrV4 Spring Steel Strip
51CrV4 is a hardened and tempered carbon steel strip suitable for a range of applications including spring-type components. Ovako produces this grade in various gauges from 0.5mm to 2.00mm with coil widths up to 2000kg per bundle.
The addition of vanadium refines the steel grain, reducing overheating sensitivity and improving strength and toughness. This makes it ideal for making larger and chopper knife types.
Hardening and Tempering
51CrV4 is a high-alloy steel that exhibits a good combination Stainless Spring SteelStrip of mechanical properties, such as tensile strength, elongation at fracture, and hardness. The excellent ductility of the spring steel is achieved by the addition of elements such as manganese, vanadium, and chromium. However, the mechanical properties of the alloy are highly dependent on heat treatment.
The heat treatment process involves soaking, quenching, and tempering. The soaking and quenching temperatures have a significant effect on the microstructure, namely, the tempered troostite, as well as the mechanical properties. Several studies have studied the effects of the soaking and quenching conditions on the microstructure and mechanical properties of 51CrV4 spring steels. However, few studies have focused on the quenching parameters, especially the oil-bath temperature and the out-of-oil workpiece temperature.
To obtain a good combination of tensile strength and toughness, the EN47 strip is tempered in an oil bath at temperatures of 400-600°C for one hour per 25 mm of strip width. The tempering temperature of the spring steel depends on the desired final hardness and ductility. Higher tempering temperatures produce a harder and more brittle final product, while lower tempering temperatures yield a softer and more ductile material. The elongation at fracture and the area reduction at fracture are also influenced by the tempering temperature. The elongation at fracture and area reduction at fracture of the tempered 51CrV4 steel strip increase with an increasing oil-bath temperature, while the hardness decreases.
Chemical Composition
51CrV4 is a Chromium Vanadium alloy steel supplied in the as-rolled and spheroidize annealed condition. It is a good spring steel for components subject to stress, shock or vibration, such as axles, crankshafts, connecting rods, compression springs and valve springs. The chromium content in this grade makes it a better choice than carbon grades where distortion is a concern.
When cold-rolled, it has a low yield strength of 550MPa and tensile strength of 720 MPa. It is also easy to machine and can be cold-formed with good ease, but the machinability in the direction of the grain is poor.
AISI 6150 alloy is a common choice for larger knives and chopper knives. It is a fine spring steel for these types Tinplate Sheet supplier of applications and works well at the higher loads that they are designed to operate at.
When forming this alloy, the forging temperature should be between 2150 and 1600oF (1070 and 870oC). After forging, it should be spheroidized to improve its machinability. Spheroidizing reduces the oxygen potential, changes the microstructure from coarse lamellar pearlite to coarse spheroidite, and increases its hardness by approximately 10-20 HRC. This change in microstructure also helps to improve the machinability of this alloy in the directions of the grain. After spheroidizing, it can be quenched in oil. It is recommended to temper immediately after quenching and while tools are still warm.
Mechanical Properties
51CrV4 (DIN 1.8159) spring steel, also known as DIN 6150 steel or AISI 6150 steel, is an alloy steel that has great mechanical properties and processing performance. It is often used to make large cross section, high load important springs. It also offers excellent toughness with shock resistance, making it a good alloy spring steel for parts that are exposed to stress, shock and vibration.
The mechanical properties of this steel are closely related to the quenching conditions, especially the soaking temperature and cooling rate. Therefore, the present work studied the effects of different oil-bath temperatures and out-of-oil temperatures on the microstructure and mechanical properties of this material. The morphological examination focused on both the as-quenched martensite and the tempered troostite, and tensile and hardness tests were performed to evaluate the mechanical properties.
The results indicated that a high oil-bath temperature increased the chance of auto-tempering, which shortened the length of martensite laths and enhanced the width of the carbide particles in the final tempered microstructure. In addition, a high out-of-oil temperature resulted in a larger distribution of bainite islands and enhanced the intercarbide spacings in the tempered microstructure. The ductility of the experimental steel was greatly enhanced, which was in agreement with the improved fracture toughness calculated from the FE analysis.
Applications
51CrV4 steel strip is a spring-type material, and can be used for torsion and bending stress resistant applications such as brake pads, clutch plate segments, shears and wire-cutting scissors. This grade is also suitable for general engineering and motor vehicle components such as crankshafts, steering knuckles, gears and spindles.
It is a chromium vanadium alloyed heat treatable steel. The addition of vanadium to this grade makes the crystalloid particles smaller, decreases the overheating sensitivity and raises the strength and toughness of the steel. This makes it very hard and abrasion resistant, and is therefore an excellent choice for tool steel.
The steel can be cold rolled, hot rolled or formed to different shapes and sizes. It can be welded, but special precautions should be taken due to its high chromium content. Preheating and post-weld heat treatment is recommended to avoid cracking.
Forging is possible, but should be performed between 1050°C and 840°C to avoid cracks. It should then be normalized between 850°C and 870°C before cooling in air.
