1055 is pure carbon steel having an optimum combination of durability and toughness. This type of steel usually has comparable strength and edge retention as other stainless steel knives. 1055 carbon steel is not exactly lie in the range of high carbon steel that’s why it has lower brittleness and useful impact resistance.
Plain carbon steel usually has lower casting temperature and low heat treatment cost which makes them ideal for budget applications.
1055 carbon steel Composition
|C||0.50 - 0.60|
|Mn||0.60 - 0.90|
Composition are taken from Matweb.
1055 carbon steel properties
|Melting Point||1410 C|
For hardness test, you can review;
|Yield Strength||560 Mpa|
|Poisson ratio||0.27 - 0.3|
|Elastic Modulus||195 GPa|
|Machinability (Based on AISI 1212 steel as 100 mahinability)||55|
|Thermal Conductivity (W/m. K)||49.8|
|Thermal Expansion [µm/m.K from 20 C]||11|
|W1 Steel||Electrical resistivity (ohm - cm)|
Plain carbon steel usually has an excellent response to forging, and the same goes for this carbon steel. Steelmakers perform forging on this steel at a temperature in between 925 and 1205o C. The forging process improves mechanical properties and, also, causes the development of lots of stresses within 1055 steel. This is why steel is transferred to annealing furnace after forging before any further treatment.
1055 grade is American grade of plain carbon steel with carbon content in a range of 0.55 – 0.6% C. This grade usually comes in the hypo eutectoid steel region which under equilibrium cooling contains a ferritic matrix with Pearlitic grains.
The microstructure development can be seen in the hypo eutectoid microstructure section of Annealing steel.
As discussed above, steel makers usually use full annealing process after forging to relieve stresses before any post forging heat treatment.
Full annealing is a process that involves heating the steel to the austenite region to achieve a uniform gamma phase. The full annealing process can be studied further on, “Annealing types”.
For this carbon steel, the full annealing cycle consists of heating the steel to a temperature of 790oC – 870oC and soaking it to get a uniform structure. After soaking, it is cooled to a temperature of 650o C slowly i.e. 28oC per hour. At this temperature, steel makers perform soaking to achieve uniform temperature at the center and surface of the steel to avoid distortion of steel due to thermal stresses. The distortion defect due to temperature can be studied at Defect of Heat treatment and their remedies Article. From 650oC, 1055 carbon steel undergoes air cooling till it achieves room temperature.
Normalizing is the heat treatment process usually carried out to refine the microstructure and to relieve the internal stresses. Normally normalizing of carbon steel is carried out before hardening and tempering processes.
Normalizing of carbon steel involves heating to steel at a temperature of 900oC, holding there for homogenization, and then air cooling.
Hardening is a fast cooling process involves the conversion of ferrite and pearlite into martensite and retained austenite.
The hardening process for steel depends upon heating temperature and quenching media. For 1055 hardening treatment, temperature above A3 line and water quenching for smaller castings are preferred. For large castings, oil quenching is preferred to avoid quench cracks which can be found in heat treatment defects.
The development of martensite in structure results in large thermal stresses within material along with retained austenite formation. No quenching process can completely remove retained austenite. The reason can be studied in the TTT diagram in steel.
This retained austenite and martensite is converted to carbides to avoid brittleness and better machinability. Follow the Tempering steel process for stages which causes the conversion of retained austenite and martensite into carbides.
Temperature for tempering is selected in response to the mechanical properties required. For achieving the right mechanical properties, the relation between tempering and hardness should be carefully understood.
Normally temper cracks are developed in 1055 carbon steel if performed tempering in between 260 – 315o C. So, best practice to perform tempering below 300oC.
Disadvantage of 1055 carbon steel
Although this grade steel has excellent toughness properties they have little or no strain resistance.
With optimum properties in terms of machinability, hardness, and edge retention ability, this steel is considered an idea for kitchen knives. With no corrosion-resistant alloying addition, this steel is prone to rust and may turn black with excessive use.
1055 carbon steel Applications
Common Applications of 1055 plain carbon steel are;
- Kitchen Knives
- Folding knives
- Hot upset forging dies
- Hand tools
- Battering tools
1055 steel for decorative swords
1055 steel swords provide excellent durability and suitable for practice and display swords. This grade of steel offers adequate shock resistance and lower resistance. Unlike high carbon steel, this grade does not suffer from brittleness and can be extensively used for Japanese katana swords after deep forging processes.
One more benefit of 1055 swords is the low cost of manufacturing. This grade can be easily melted with a lower rejection rate in forging and heat treatment giving low-cost knives, swords, and axes for day to day use.