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 1018 Carbon Steel
SAE AISI(*) 1018 (G10180**) and 1020 (G10200**) mild/low carbon steel grades are very similar. Both SAE AISI 1018 steel and SAE AISI 1020 (see separate product presentation) carbon steels are iron alloys with their alloy composition being basically identical. Please refer to the attached charts for the comparison of SAE AISI 1018/1020 steel properties. For each property being compared, the top bar refers to 1018 and the bottom bar to 1020 steel. An overview of their properties and fabrication processes is provided below.
SAE AISI 1018 mild/low carbon steel has excellent weldability and produces a uniform and harder case and it is considered as the best steel for carburized parts. This alloy offers a good balance of toughness, strength and ductility. Provided with higher mechanical properties, AISI 1018 hot rolled steel also includes improved machining characteristics and Brinell hardness.
AISI 1018 Mild/Low Carbon Steel can be used in different applications including:
- bending, crimping and swaging processes
- carburized parts that include worms, gears, pins, dowels, non-critical components of tool and die sets, tool holders, pinions, machine parts, ratchets, dowels and chain pins use AISI 1018 mild/low carbon steel
- fixtures, mounting plates and spacers
- applications that do not need high strength of alloy steels and high carbon
- It provides high surface hardness and a soft core to parts that include worms, dogs, pins, liners, machinery parts, special bolts, ratchets, chain pins, oil tool slips, tie rods, anchor pins, studs etc. Also used to improve drilling, machining, threading and punching processes or prevent cracking in severe bends.
AISI 1018 Carbon Steel is suited for fabrication processes such as welding, forging, drilling, machining, cold drawing and heat treating briefly discussed below.
Heat Treatment
The AISI 1018 mild/low carbon steel can be heat treated with the following processes:
Normalizing
AISI 1018 mild/low carbon steel should be heated at 890°C – 940°C and then cooled in still air.
Forging
This process requires heating between 1150°C – 1280°C and AISI 1018 mild/low carbon steel is held
until the temperature becomes constant.
•900°C is the minimum temperature required for the forging process.
•The steel is then cooled in air after this process.
Tempering
AISI 1018 mild/low carbon steel is tempered at between 150°C – 200°C for improvement of case toughness. This process has little or no effect on hardness. The occurrence of grinding cracks is reduced when AISI 1018 mild/low carbon steel is tempered at the
above mentioned temperature.
Annealing
The AISI 1018 mild/low carbon steel is heated at 870°C – 910°C and allowed to cool in a furnace
Stress Relieving
500°C – 700°C is required to relieve stress in AISI 1018 mild/low carbon steel that is later cooled down in still air.
Case Hardening
This process requires heating to be carried out between 780°C – 820°C. AISI 1018 mild/low carbon steel is then quenched in water.
Core Refining
This is an optional process that requires heating at 880°C – 920°C. AISI 1018 mild/low carbon steel after being heated is moistened in oil or water.
Carburizing
Carburizing takes place at 880°C – 920°C.
Machining
The machinability of AISI 1018 mild/low carbon steel is graded at 78% of B1112.
Welding
AISI 1018 mild/low carbon steel can be instantly welded by all the conventional welding processes. Welding is not recommended for AISI 1018 mild/low carbon steel when it is carbonitrided and carburized.
Low carbon welding electrodes are to be used in the welding procedure, and post-heating and preheating are not necessary. Pre-heating can be performed for sections over 50 mm. Post-weld stress relieving also has its own beneficial aspects like the pre-heating process.
Sourced from quality producers, SAE AISI 1018 and 1020 low carbon steel tubes are offered as part of our own branded (AVIATIONEU NEW ERA) product lines in different forms (cross sections), round, square, rectangular, etc. and dimensions in inches or millimeters (depending on the supplier) to meet project requirements. In the case of round tubes, they can be furnished Normalized, Annealed or other conditions, in different specifications in pre cut or cut to order lengths. For those in Metric system outer diameters and wall thicknesses are specified in mm and lengths in meters or centimeters. For those in inch system outer diameters and wall thicknesses are in inches and lenghts in inches or feet.
Appearing prices for pre cut tubes are per piece in indicated dimensions. For additional information please refer to the supplied documentation. 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.
(*) 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.