420B STAINLESS STEEL
There are many types of stainless steel available. Stainless steel is identified in accordance with microstructure. Different chemical composition relates to mechanical properties and other distinction.
Different steel grade exhibits distinct mechanical properties. It is important to understand the small unique dissimilarity between the uncountable stainless steel grades. Choosing the best grade will conduct the right application in the engineering sector.
Stainless steel has one significant application in biomedical applications. It is known as surgical steel. Strength and corrosion resistance ability is designated characteristic for surgical steels. Surgical steel is commonly used in orthopedic and dental implants. It is also used in surgical instruments like forceps, retractors, etc
Martensitic stainless steel shows strength, durability, and moderate corrosion resistance. It shows considerable ductility and machinability.
420B is a martensitic grade and is used in surgical steels.
Grade 420B
Grade 420B is a high carbon version of grade 420 stainless steel. It is high carbon content which optimizes hardness. Like grade 420, grade 420B stainless steel can be hardened by heat-treatment. Grade 420B is martensitic stainless steel for instruments. It offers optimal hardness and good resistance.
Weldability is poor for AISI 420B . Fabrications of martensitic stainless steel required hardening and tempering operations. Grade 420B is not used for high temperatures, as it attains softness and loss of corrosion resistance.
Good corrosion resistance and hardness are the attributes that make it ideal for its application. AISI 420B is widely used in surgical and dental instruments, scissors, pump and valve parts, etc.
COMPOSITION
Grade 420B is high carbon with low chromium stainless steel. It contains 0.26 -0.35 % carbon and 12-14% chromium with traces of silicon, manganese, sulfur, and phosphorous.
PHYSICAL PROPERTIES
Grade 420B attains a metric density of 7.73 g/cm3.
The modulus of elasticity is 195Gpa.
Electrical resistivity is 68 Microhm-cm.
THERMAL PROPERTIES
Thermal expansion coefficient is 10.2 µm/m° at 1-100°C
Thermal conductivity is 27.4 W/mK at room temperature.
MECHANICAL PROPERTIES
In annealed conditions, Grade 420B attains a tensile strength of 800 Mpa and yield strength of 650 Mpa.
Hardness is 245 HB.
Elongation is 10%.
MAGNETIC PROPERTIES
Grade 420B shows magnetic permeability in annealed and heat-treated conditions.
HEAT TREATMENT
Annealing
Grade 420 can be annealed by heating its temperature from 840-900 °C. Then slow furnace cooling takes plate till 600°C, followed by air cool.
Hardening
Material is heated in a temperature range of 980-1035 °C, followed by oil quenching.
Oil quenching is suggested for heavy segments.
Tempering
Tempering is done in the temperature range of 150-370°C. Tempering at this temperature enables high hardness and improved mechanical properties.
PROPERTIES
CORROSION RESISTANCE
Grade 420B attains maximum corrosion resistance under hardened conditions. It offers good corrosion resistance in mild environments. Grade 420B offers corrosion resistance to fresh water, alkalis, air, food, and mild acid. It provides corrosion resistance ammonia, blood, sterilizing solutions, carbonic acids, crude oil, detergents, dilutes nitric acids, steam, and vinegar.
A polished and smooth surface finish tends to give excellent results. The corrosion resistance property of grade 420 falls under annealed conditions. It is not suggested to be used in the annealed condition.
Austenitic grades offer more corrosion resistance than grade 420.
WELDING
Grade 420B emits limited weldability, as it has a hardened structure
APPLICATIONS
Good corrosion resistance and hardness are the characteristics that make it ultimate for its application. Grade 420B is commonly used in dental and surgical instruments. Other common applications for grade 420 are as follows:
- Surgical equipment
- Needle valves
- Knife blades
- Hand tools
- Fasteners
Ambica steels offer superior fine quality grades 420B bars. A grade 420B is a special grade produced by Ambica steels. Bars are available in round, square, flat, hexagonal, and customized shapes. Inquiry and orders are welcome.
