DC53 STEEL

DC53 was initially developed with the Wire EDM process in mind. The high temperature double draw 520° C (970° F) or higher was part of the development criteria in determining alloy content, and heat treat requirements for DC53. This high temperature double temper relives a considerable amount of stress in the steel which in turn minimizes movement in the part when Wire EDM cutting hardened DC53. Click here for more information.

With special care DC53 can be welded. Use any appropriate weld rod such as an H72A rod which is commonly used for high carbon, high chrome die steels similar to D2. The weld rod should be dry to prevent bubble cracks in the weld. Placing the rod in a 350 degrees Celsius (650 degrees Fahrenheit) oven for one hour is generally sufficient.

Click here for additional information on DC53 Welding.

Air hardening DC53 is best accomplished under vacuum. First, preheat and hold at 800° C (1,475° F) to 850° C (1,560° F) until the part is uniformly heated and then increase the heat to 1,030° C (1,885° F) to Austenitize, otherwise known as soaking the tool. Austenitize 25 to 30 minutes per inch at temperature (to be safe, minimum austenitize time for smaller parts under 1 inch can be up to 1 hour) up to 4 inches thick in cross section and 10 to 25 minutes per inch for thickness over 4 inches before inert gas pressure quenching (Generally in nitrogen), to rapid cool with 2 times atmosphere pressure (2 bar) or high velocity equivalent. To be safe, longer times are acceptable while shorter times are not.

Quench rates using 3 bar pressure or higher are not recommended due to the potential for distorting and the higher stress involved. The quenching phase converts the majority of the tool steel from the austenitic state to an un-tempered martensite condition. The part should then be immediately tempered once it has reached 45° C (120° F). Be sure to check hardness at this point to assure that the part has reached the desirable hardness if at least 64 HRC.

Per-heat the part to 850° C (1,550° F) until uniformly heated. Austenitize in a molten salt bath at 1,030° C (1,885° F) for a minimum of 5 minutes. See chart below for details. Salt quench and then allowed to slow cool in still air to 45° C (120° F) to 65° C to (150° F) before tempering.

Material growth .10% to .15% (.001” to .0015” per inch).
An optional third temper recommended for intricate high
precision components requiring EDM work or PVD coatings.

Tempering is commonly performed in a non-atmosphere controlled convection furnace. The first temper should be conducted as soon as the part can be handled at about 45° C (120° F) to 65° C to (150° F). The part should be allowed to cool to ambient temperature between subsequent tempers.

To achieve HRC 60-62, temper DC53 twice at 540° C (1,005° F) for 60 to 90 minutes per inch in thickness in cross section. The minimum tempering time is 90 minutes. Temper twice at 520° C (970° F) for the same amount of time to achieve HRC 62-64. A hardness les than HRC 60 is not generally recommended for most punch and die components due to insufficient compressive strength typically needed for stamping applications. Applications requiring additional toughness can be double tempered at 550° C (1,020° F) to achieve HRC 58-60.

If size change or distortion of hardened DC53 due machining, grinding, applying surface treatments or wire EDM work is a concern in high precision applications, an optional third temper of 400° C (750° F) can be applied to the initial heat treat process. This final tempering temperature is high enough to temper the remaining un-tempered martensite, but not high enough to convert additional retained austenite resulting in a more stable structure. The third temper is typically not necessary if the tool has been hardened using the salt bath process.

Conducting a hardness test after the heat treat process is complete is just one method used to measure the quality of heat treat. For additional quality assurance, it is also recommended that a precise dimensional measurement be taken from a given feature both before and after the entire heat treat process to assure that the proper amount of growth has taken place. Properly heat treated DC53 can be expected to grow approximately .1% to .1 ½% (.001” to .0015” per inch) of its original size before hardening. Shrinkage of the tooling can be a sign of problems in the hardening and or tempering process and is generally attributed to excessive amounts of retained austenite.

As when tempering most tool steels, vacuum tempering is a more difficult process to control than convection tempering and fluctuations in hardness results are to be expected. It should only be used when absolutely necessary and ideally be limited to smaller parts with a simple geometry.

Freezing at 185° C (-300° F) between the first and second temper may also be beneficial to toughness however, specific data is not readily available. It is important to note that cryogenics should always be followed by a temper.

For special applications, DC53 can also be forged into many shapes. The temperature for forging is between 900° C (1,650° F) and 1,100° C (2,010° F). Annealing after forging in highly recommended to minimize stress in the part and assuring optimum heat treat response.

DC53 can be annealed by uniformly heating the part to 800° C (1,475° F) to 850° C (1,550° F), and holding for 2 hours followed by a slow cooling at no more than 27° C (50° F) degrees per hour to until the it has dropped below 500° C (930° F). The part can then be removed from the furnace and allowed to continue to cool in still air to room temperature. If decarburization is a concern, annealing vacuum is recommended. In order to minimize size change, the pre-coating and post heat treat will need to be as similar as possible.

For heat treat and application processing purposes, surface treatment processes can be broken down into two categories, Cold Process and Hot Process. Surface treatments applied below 480°C (900°F) which is lower that the substrate tempering temperature is considered a cold process treatment.

Nitriding and PVD coating treatments fall into the Cold Process category because the temperatures which they are applied at are more than 28°C (50°F) below the tempering temperature of most potential substrate tool steels and therefore, should not affect the integrity of their initial heat treat. Tool steels such as S7, A2, and D2 typically do not meet this requirement. DC53 however, when tempered at or above 540°C (1,000°F) is not affected by these processes and will maintain original size and heat treat characteristics. For intricate or large tools needing optimum size stability, third temper of at least 400°C (750°F) can be applied. DC53 with a Case Harden Nitride and or PVD coating are excellent for precision tooling components.

CVD and TD coatings are considered Hot Process surface treatments because they are applied at from 925°C (1,700°F) to 1,040°C (1,900°F). The higher temperatures typically mean better coating adhesion due to diffusion of carbon alloy elements. These temperatures exceed the tempering temperatures and fall within the austenitizing range (Hardening temperature range) of most potential substrate materials and greatly affect the integrity of the initial heat treat. Distortion and dimensional stability in the form of growth by of as much as .15%, or 0,0015mm per millimeter (.0015” per inch) is to be expected. Because this is a percentage change, larger tools will see more overall size change than small tools.

Nitriding is a process which case hardens the existing surface of the tool steel. The most common ways to apply nitriding are: salt bath, fluidized bed and ion nitride. Although this process can be applied at nearly 535°C (995°F) potential damaging the substrate tool steel heat treat can be avoided by choosing a process which is at least 10°C (50°F) below the tempering temperature of the substrate material and by keeping the case hardening depth to a minimum. The recommended case hardened depth for most stamping applications should not exceed 0,025mm (.001”). By keeping the case depth shallow, it minimizes the heat exposure and prevents the formation of a white layer on the surface making it brittle and prone to chipping and breakage. Shallow case Fluidized Bed or Ion nitriding applied below 500°C (930°F) work best for DC53.

Surface treatments such as Titanium Nitride (TiN), Titanium Carbonitride (TiCN), Chrome Nitride (CrN) & Titanium Aluminum Nitride (TiAlN) applied using the PVD process are coatings on the surface of the steel. These coatings are very thin typically measuring less than .025mm (.0001”). Because they have very little support of their own and require significant heat to be applied, these coatings should only be applied to tool steels with sufficient obtainable hardness of HRC 60 after being exposed to coating process temperatures as high as 480°C (900°F). For DC53, the standard two tempers at or above 520°C (970°F) perform well. A third temper at 400°C (750°F) is recommended for intricate and high precision applications.

There is a correlation with a coating process temperatures and coating adhesion. Higher coating process temperatures typically mean better coating adhesion due to diffusion of carbon and alloy elements. There are also minimum temperature limits as to how low of a temperature some coatings such as Titanium Carbide (TiC) can be applied. While adhesion improves and additional coating materials become available for this process, precision is diminished due to the high process temperatures involved.

CVD coatings are applied between 925°C (1,700°F) and 1,040°C (1,900°F) which is equivalent to the hardening temperature and well above the tempering temperature of nearly all potential substrate tool steels. This will require some form of post coating heat treat because the high coating process temperature has pushed the tooling up into the hardening temperature range, affecting the structure of the steel. The tool hardness will likely be unacceptably low and un-tempered which reduces its toughness and strength.

Ideally, tooling that has been CVD coated should be annealed and re-heat treated after these surface treatments are applied. The reason tools are heat treated prior to the coating process is because its size from the annealed state to the hardened state otherwise known as the martensitic (Hard) state differs and it is not always possible to predict how much size change will occur when hardening. A tip to minimize the growth of DC53 when CVD coating, is to temper at 500°C (930°F) to 510°C (950°F) in the heat treat before coating process.

These coating are applied at between 1,010°C (1,850°F) and 1,030°C (1,886°F) and can be handled similar to CVD coating however, they can also utilize the coating process itself as a part of the reheat treating process. By using the proper salt bath temperature in the coating process, it can be used to also hardening harden the tool steel. For optimum hardness DC53 should be TD coated at 1,030°C (1,886°F). This process is followed be multiple tempers at the appropriate temperatures to achieve the desired hardness. In order to achieve optimum tool life, it is recommended to anneal and reheat treat the tool.

Tools should be finished to size and polished prior to applying the surface treatment. A light polish after coating is also beneficial. This is particularly important when applying surface treatments on form, draw, and extrusion tools.

Higher temperature surface treatments utilizing the CVD and TD process coatings should be annealed, re-hardened, and tempered for optimum tool life.

In general, surface treatments can reduce the coefficient of friction and improve wear resistance. Higher hardness of the substrate material offers superior strength reducing plastic deformation resulting in optimum coating adhesion. Understanding the difference in precision capabilities based on the process temperatures and the specific properties of the coating themselves are important. Contact your surface treatment supplier for details on specific surface treatments.

Applications

FB punches for hook-shaped electric appliance components. Long, thin shape promotes severe conditions.

Results

Considerations

Conventional Steel–Cracking and fracturing at the tip of the long, thin shape, shortened life.

DC53–Because of DC53’s excellent toughness, hardness could be increased, resulting in more than double the life.

Application

Injection molds for electromagnetic switch boxes. Since the material worked is FRP resin, wear in the area surrounding the gate is particularly problematic.

Results

Considerations

Conventional Steel–The mold was discarded due to wear occurring in areas surrounding the gate and where the flow of resin became irregular.

DC53–Applying the highest hardness of DC53 (HRc63) proved highly effective in combating simple wear.

Application

Working of bushings by backward extrusion.

Results

Considerations

Conventional Steel–Wear of punch edge and galling lateral face shortened durability.

DC53–To prevent wear and galling, hardness of DC53 was tempered at a high level, resulting in expected extension of life (due to its high toughness, this material resists cracking.)

Application

Flat thread rolling dies for working stainless steel bolts where there is a particularly high working load.

Results

Considerations

Conventional Steel–Chipping and local seizing of threads, required early regrinding.

DC53–In working with stainless steels, high toughness, high hardness, and high resistance to temper softening are necessary. DC53 proved effective.

Application

Straightening of heat-resistant steel and stainless steel where pitting of the roll is a major problem and high hardness and toughness are required.

Results

Considerations

Conventional Steel–Pitting of roll surface and local seizing occurred, terminating life.

DC53–The basic characteristics of DC53 fully met the requirements for high toughness to prevent pitting and high hardness to prevent seizing.

Application

This type of die is commonly used. Surface hardness treatment is applied depending on the material worked and the precision of the finish required.

Results

Considerations

Conventional Steel–Chipping of the cutting-edge and insufficient base hardness of the die led to termination of life.

DC53–To increase the effectiveness of surface treatment, higher base hardness of the die should be considered. High hardness of DC53 proved effective.

Application

Shear blades to slit all types of steel sheet, particularly high-tensile steel sheet or thick plate where chipping of the blade edge is problematic.

Results

Considerations

Conventional Steel–Chipping of the cutting-edge and insufficient base hardness of the die led to termination of life.

DC53–To increase the effectiveness of surface treatment, higher base hardness of the die should be considered. High hardness of DC53 proved effective.