O1 – D2
O1 – BS4659 BO1
O1 Tool Steel is an electric-furnace melted, oil-hardened, non-shrinking, general-purpose tool steel. It is chemically composed of approximately 0.95 percent carbon, 1.1 percent manganese, 0.6 percent chromium, 0.6 percent tungsten and 0.1 percent vanadium. The hardening temperature of O1 tool steel is between 790 degrees Celsius and 820 degrees Celsius.
O1 Tool Steel is not easily abraded, has high surface hardness post tempering, does not deform during hardening and can be machined well.
Further, it also has a low hardening temperature (and, therefore, can be heat treated in homes and shops), and does not lose shape during quenching.
It is inexpensive and readily available. O1 Tool Steel is ideal for making tools and knives, as it can be easily sharpened.
Strength and Hardness
Strength of a metal determines the extent to which it may deform when load is applied on it. Strength can be measured based on various parameters, such as the maximum ability to take strain, resistance to wear and tear, impact handling, or how the material performs when subjected to frequently changing load conditions. Strength generally increases as the carbon and manganese content increases. Given the high percentage of both of those, O1 Tool Steel is strong.
Hardness of a material indicates its resistance to get indented that is not temporary (i.e.; it persists even after the load conditions are removed, as opposed to the strength that is an indication of its performance only when the load is applied), and carbon is also the primary hardening element in steel. The Rockwell method measures the hardness of O1 Tool Steel to be in the range of 64 RC to 58 RC (this is the most commonly used measurement technique).
Toughness and Brittleness
Toughness of a material determines whether it can be subjected to shock conditions, and the extent to which it may undergo deformity in shape but still not snap. If subjected to a proper treatment process, O1 Tool Steel tends to be very tough. As opposed to toughness, brittleness measures whether a material will snap instead of getting deformed, when load is applied. Alloy steels like O1 Tool Steel are less brittle than cast or pig iron because of the presence of magnesium.
Ductility and Malleability
Ductility is a material’s ability to be drawn into wires without breaking. Ductility decreases with increasing carbon, and because O1 Tool Steel has a very high carbon content, it is not very ductile. On the other hand, malleability determines a material’s ability to be rolled into sheets without getting ruptured. Since O1 Tool Steel has little or no residual elements like copper, nickel or molybdenum, it is quite malleable and can be worked upon even at low room temperatures.
It is essential to heat evenly and consistantly at the required tempering temperatures and that the temperature is maintained for one hour per inch of total thickness of the metal undergoing tempering.
D2 – BS4659 BD2
D2 tool steel is an air hardening, high-carbon, high-chromium tool steel possessing extremely high wear resisting properties. It is very deep hardening and is practically free from size change after proper treatment. This tool steel’s high chromium content gives it mild corrosion resisting properties in the hardened condition.
D2 tool steel has found application in: Blanking dies, Forming dies, Coining dies, Extrusion dies, Drawing dies, Forming rolls, Edging rolls, Beading rolls, Master tools, Heading tools, Long punches, Intricate punches, Slitting cutters
Typical Mechanical Properties
High-carbon, high-chromium steels such as D2 tool steel achieve their excellent wear resistance due to a chemical balance which renders them notch sensitive and low in ductility. Meaningful tensile data are unavailable. The practical experience indicates that compressive loads in excess of 400,000 psi (2758 Mpa) can be withstood if evenly applied at low rates of loading.
D2 tool steel is extremely sensitive to overheating during hardening. It is therefore imperative that care be taken to insure that the hardening temperature is within the recommended range of 1800/1875°F (982/1024°C). If overheated, D2 tool steel, like other high-carbon, high-chrome tool steels, will not reach its maximum obtainable hardness and will shrink badly. Don’t overheat it. Without preheating, place the tool right in the hot furnace and let it heat naturally until its color uniformly matches the color of the thermocouple in the furnace. Tools should be soaked at temperature 20 minutes plus 5 minutes for each inch of thickness, the quenched in air. Control of decarburization can be achieved by using any one of the several modern heat-treating furnaces designed for this purpose. If endothermic atmospheres are used a dew point between 20/40°F (-6.7/+4.4°C) is suggested. In older type, manually operated exothermic atmosphere furnaces, an oxidizing atmosphere is required. Excess oxygen of about 4 to 6% is preferred. If no atmosphere is available, the tool should be pack hardened or wrapped in stainless steel to protect its surface.
D2 tool steel has two toughness peaks, one at 450°F (232°C) and the other at 700°F (371°C). For the best combination of toughness and hardness, temper at 450°F (232°C). While this is the best tempering temperature for practically all applications, greater ductility can be obtained by tempering at 700°F (371°C), although there will be some sacrifice of hardness. Double tempering is desired with the second temper 25°F (13.8°C) below the first temper. The hardness curve for D2 tool steel shows the same “kickback” or secondary hardening found in high-speed steels. In this material, it occurs at 1000°F (538°C) and, if by accident tools have been overheated in hardening, causing shrinkage and loss of hardness, they might be salvaged by tempering them at 1000°F (538°C). They will regain some of their lost hardness and will expand close to their former size. The hardness values given in the chart at 1000°F (538°C) are based on 1 hour soaking time. Longer soaking time will result in somewhat lower Rockwell C hardness. Since D2 tool steel maintains a high hardness after a 1000°F (538°C) temper, it lends itself well to gas nitriding or liquid cyaniding. This provides added wear resistance for forming tools.
To relieve machining stresses for greater accuracy in hardening, first rough machine, then heat to temperature of 1200/1250°F (649/677°C) and slowly cool. After cooling, the part or parts may be finish machined.
Tool steel refers to a variety of carbon and alloy steels that are particularly well-suited to be made into tools. Their suitability comes from their distinctive hardness, resistance to abrasion, their ability to hold a cutting edge, and/or their resistance to deformation at elevated temperatures (red-hardness). Tool steels are generally used in a heat-treated state. With a carbon content between 0.7% and 1.4%, tool steels are manufactured under carefully controlled conditions to produce the required quality. The manganese content is often kept low to minimize the possibility of cracking during water quenching. However, proper heat treating of these steels is important for adequate performance, and there are many suppliers who provide tooling blanks intended for oil quenching.
Tool steels are made to a number of grades for different applications. Choice of grade depends on, among other things, whether a keen cutting edge is necessary, as in stamping dies, or whether the tool has to withstand impact loading and service conditions encountered with such hand tools as axes, pickaxes, and quarrying implements. In general, the edge temperature under expected use is an important determinant of both composition and required heat treatment. The higher carbon grades are typically used for such applications as stamping dies, metal cutting tools, etc. Tool steels are also used for special applications like injection molding because the resistance to abrasion is an important criterion for a mold that will be used to produce hundreds of Alloy steel is steel alloyed with other elements in amounts of between 1 and 50% by weight to improve its mechanical properties. Alloy steels are broken down into two groups: low alloy steels and high alloy steels. Low alloy steels are defined as having an alloy contents between 1 and 4% and high alloy steels have 4 to 50% alloying contents. However, most commonly alloy steel refers to low alloy steel. These steels have greater strength, hardness, hot hardness, wear resistance, hardenability, or toughness compared to carbon steel. However, they may require heat treatment in order to achieve such properties. Common alloying elements are molybdenum, manganese, nickel, chromium, vanadium, silicon and boron.