Carbon Steels

In accordance with the definition of the American Iron and Steel Institute (AISI) the term carbon steel (aka plain carbon steel) is applicable to material:

- when no minimum content is specified or required for chromium, cobalt, columbium [niobium], molybdenum, nickel, titanium, tungsten, vanadium or zirconium, or any other element to be added to obtain a desired alloying effect, or

- when the specified minimum for copper does not exceed 0.40 percent, or

- when the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65, silicon 0.60, copper 0.60.

The Carbon Steel grades are derived by difference in the content in the material composition. These differences influence the Carbon Steel density. The density involves the weight, tensile strength and some other mechanical properties of the material. The addition of the elements in the right quantities to the carbon steel composition enhance strength, reduce brittleness  and makes carbon steel grades suitable for different applications such as ship building, wire construction, vehicle bodies, fencing, gates and railings. 

As a group, carbon steels are by far the most frequently used steels. Their producers offer different grades of Carbon Steel materials with variations in prices.

There are four major types of carbon steel: Low Carbon Steel (aka mild steel), Medium Carbon Steel, High Carbon Steel and Very High or Ultra Carbon Steel. Their characteristics and uses are briefly discussed in the Category presentation.

AISI 1020 Carbon Steel 

SAE AISI(*) 1018 (G10180**) & 1020 (G10200**) mild/low carbon steel grades are very similar. Both SAE AISI 1018 steel (see separate product presentation) and SAE AISI 1020 carbon steels are iron alloys with their alloy composition being basically identical. Please refer to the supplied documentation for the comparison of SAE AISI 1018/1020 steel properties. An overview of AISI 1020 Carbon Steel properties and fabrication processes is provided at the Product Description section. Technical data of supplied materials should be used ONLY FOR REFERENCE, NOT FOR DESIGN, and any decisions on their use remain entirely at the buyer discretion.

SAE AISI 1020 steel, aka C1020 steel in cold worked condition, is one of the most commonly used plain carbon steels. It is a low hardness and tensile strength carbon steel alloy with Brinell hardness ranging between  119 - 235 and tensile strength between 410 - 790 MPa. It features high machinability, high strength, high ductility and good weldability by most welding processes supporting its use in all industrial sectors. Due to its low carbon content, it is resistant to induction hardening or flame hardening but carburization or carbon nitriding can be applied to achieve a hardness value of more than  Rc65.  Normally used in turned and polished or cold drawn conditions.

This alloy is used for many semi-finished products, such as square steel bars, flat steel bars, round steel bars, steel plates.

Applications: Truck, automotive and agricultural equipment parts such as axles, mechanical parts, cold head bolts, motor shafts, pump shafts, ratchet, light gear, gear drives, worm gear, spindle, seat bracket, crane-cable drum, motor-brake wheel, etc. Also commonly used in the manufacturing of race cars and motorcycle frames. 

AISI 1020 carbon steel is equivalent material to those produced under European EN (Germany DIN EN, British BSI, French NF…), Japanese JIS and Chinese GB standards.

Hardening

AISI 1020 carbon steel can be hardened by cold working and by heat treatment, quenching and tempering.

Heat Treatment

AISI 1020 carbon steel can be hardened by heating between 815- 871°C (1500 - 1600°F), which should be followed by water quenching. Then it should be tempered.

Heat Treatment includes normalizing, annealing, austenitizing, etc. 

Hot Working

AISI 1020 carbon steel can be hot worked in the range of 482 to 649°C (900 to 1200°F).

Cold Working

Cold working AISI 1020 carbon steel is possible using all the conventional methods. In case of prolonged cold working, it is recommended that stress relief annealing be carried out.

Normalizing

AISI 1020 steel is heated at 890°C - 940°C followed by a period of holding until the temperature remains constant throughout the section. It is soaked for 10 - 15 minutes and then cooled in still air. The typical normalizing temperature is 915 °C (1675 °F). 

Annealing

Complete annealing of AISI 1020 can be achieved between 871-982°C (1600 to 1800°F) followed by slow furnace cooling. This will provide the alloy with a tensile strength of about 65 ksi. A stress relief annealing can be performed if required at 538°C (1000°F).

Recommended temperature and cooling cycle for full annealing of small carbon steel forgings (size ≤ 3 in.): Annealing temperature 855-900 °C (1575-1650 °F), cooling cycle is from 855 °C (1575 °F) to 700 °C (1290 °F), furnace cooling speed at 28 °C/h (50 °F/h), Brinell hardness is 111-149 HB.

Reheating (Austenitizing)

Reheating temperatures for hardening of  AISI 1020  steel is 760-790 °C (1400-1450 °F). Carburizing is commonly carried out at 900 to 925 °C (1650 to 1700 °F).

Carburizing

AISI 1020 is heated to between 880°C - 920°C in a suitable carburizing atmosphere followed by holding for a sufficient amount of time to produce the required carbon content and case depth. After this, refining/hardening and tempering processes are carried out to optimize the core and case properties.

Core Refining

AISI 1020 steel is slowly cooled and re-heated at 870°C - 900°C followed by a period of holding until the temperature remains constant all over the section and is quenched in water, oil or brine.

Case Hardening

After performing the core refining process, it is re-heated to 760°C - 780°C followed by a period of holding until the temperature is consistent all over the section. It is then quenched in water.

Case Hardening: The surface hardening carburization temperature of 1020 carbon steel is 970-955 °C, mostly carried out in a mixed gas of methane and carrier gas. Hardening after carburizing is usually achieved by direct quenching from the carburizing temperature into water or brine. Typical heat treatment for AISI 1020 case hardening

Carbon temperature: 900-925 °C (1650-1700 °F), cooling method: water or caustic;

Reheat temperature: 790 °C (1450 °F), cooling method: water or 3% sodium hydroxide;

Carbonitriding temperature: 790-900 °C (1450-1650 °F), cooling method: oil;

Tempering

AISI 1020 steel is re-heated followed by a period of holding for a certain time until the temperature remains constant throughout the section. It is soaked for 1 hour per 25 mm of section, and then cooled under normal atmosphere. By performing the tempering process, the toughness of the case will be improved and grinding cracks will be reduced. Temper temperature: 120-205 °C (250-400 °F), for stress relief and improving resistance to cracking (not mandatory). For stress relieving the AISI 1020 steel is heated to 650°C - 700°C followed by holding until the temperature remains constant all over the section and soaking for 1 hour per 25 mm of section. It is then cooled in still air.

Forging

AISI 1020 carbon steel should be forged at 1260°C (2300°F) down to 982°C (1800°F). Typical forging temperature is 1290 °C (2350 °F).

Welding

AISI 1020 carbon steel can be welded easily using most common welding methods. In the cold drawn or turned and polished condition, it has better weldability. It has been suggested that the welding process should not be performed in heat treated or carburized condition.

The recommended preheat and interpass temperatures for AISI SAE C1020 steel:

For thickness ≤50mm (2 in.), the recommended preheat and interpass temperature is above -12 °C (for low hydrogen); and 38 °C for other than low hydrogen.

For thickness (t) 50< t ≤100, the recommended preheat and interpass temperature is 93 °C (for low hydrogen); and 150 °C (for other than low hydrogen).

Postweld heat treatment is optional, temperature is 590-675 °C (1100-1250 °F).

Machining

Mostly used as-forged condition, since it shows good machinability in this condition (machinability rating is 65% based on 100% rating for 1212 steel). In the cold drawn or turned and polished condition, AISI 1020 steel has high machinability. Following the recommendations of machine manufacturers, AISI 1020 steel can be used for drilling, turning, milling and tapping operations using suitable feeds, tool type and speeds.

Forming

It is easy to form AISI 1020 carbon steel using all the conventional methods as this alloy is highly ductile.

Sourced from quality producers, SAE AISI 1020 steel tubes are offered as part of our own branded (AVIATIONEU NEW ERA) product lines. They can be furnished Normalized, Annealed or in other conditions, in different specifications, different shapes (cross sections), round, square, rectangular, etc. and dimensions in inches or millimeters (depending on the supplier) to meet project requirements. In the case of Metric round tubes, they are cold drawn seamless tubes available in different outer diameters and wall thicknesses in mm and pre cut or cut to order lengths in meters or centimeters. They can be furnished with plain, beveled or treaded ends and plastic caps for end protection. Those in inch system  are offered as DOM (Drawn Over a Mandrel***), with outer diameters and wall thicknesses in inches and lenghts in inches or feet.  Although they are welded tubes, the weld line becomes nearly undetectable during the manufacturing process and they are often referred to as seamless. Appearing prices for pre cut tubes are per piece in indicated dimensions.

(*) American Iron & Steel Institute (AISI), Society of Automotive Engineers (SAE).

(**)  Unified Numbering System ( UNS) Number. UNS is an alloy designation system for Metals & Alloys providing a means of correlating many internationally used metal and alloy numbering systems administered by their producers, societies, trade associations, and individual users.

(***) A process applied to tubing after it is initially constructed, allowing more exact dimensions relative to the inside and outside diameters, a smoother finish, and a better alignment of the crystal lattice structure.