How can the hardness of H13 steel reach 58HRC through heat treatment?
This can be achieved by heating and quenching at temperatures between 1050 and 1100°C, followed by oil quenching.
However, it is not necessary for hot work die steel to have such a high hardness, as its performance will be significantly reduced under high hardness.
Typically, a hardness range of HRC46-50 will provide good performance and durability.
After heat treatment of the mold, what is the surface bleached with?
- It can be washed with stainless steel acid or hydrochloric acid. Sandblasting treatment can also be adopted.
If a grinding machine is used, the processing cost may be high, the amount of material processed may be large, but the size of the product may not meet the required standard.
If hydrochloric acid fails to clean the surface, you are likely using steel with a high chromium content. Is it D2 or H13 steel?
The oxide layer on high chromium matrix steel is difficult to remove, but can be removed with an acidic stainless steel cleaner. These cleaners are readily available at mold or stainless steel stores.
- Stainless steel pickling cream works
The oxide layer on mold steels with high chromium content cannot be easily removed with hydrochloric acid. However, there are alternative methods available.
After the mold is polished with an oil stone, the surface will be smooth. You can use a coarse sharpening stone or abrasive belt for sanding before heat treatment. Then the mold can be ground again with a fine oil stone.
Another method that some people use is to first sand the mold with a fiber wheel to effectively remove the blank film. They then proceed with sanding and polishing or sandblasting.
How does the heat treatment plant treat the metal?
The heat treatment plant houses a wide range of equipment, including a batch furnace and a pit furnace.
The batch furnace is the most widely used and can handle various heat treatments such as annealing, normalizing, quenching and tempering. It is an electrically heated oven that is heated to a predetermined temperature before the part is placed inside. After reaching the desired temperature, the piece is kept warm for a while and then removed or cooled inside the oven.
The pit furnace is typically used as carburizing equipment and is buried underground. Once placed inside, the piece is sealed and then immersed in carbon-rich liquids, such as kerosene or methanol, at high temperatures. The liquid dissolves into carbon atoms, which penetrate the surface of the part.
The quenching pond is used for quenching and contains an aqueous solution or oil that is used to cool batch-type furnace hardened parts. The process involves placing the part in the tank and waiting a short period before removing it.
Other devices in the plant include high-frequency machines, which convert a 50 Hz power current into a 200 KHz current. The most common model has a maximum power of 200Kw and has a coil made of copper tube with internal cooling water placed on the outside of the part. Within seconds, the surface of the part turns red, and when it reaches the predetermined temperature, a water jacket sprays the quenching solution onto the surface to complete the quenching process.
In summary, the heat treatment plant has a variety of equipment, including those mentioned above
Why do Cr12 or Cr12MoV materials break after heat treatment?
Without information about the size and shape of parts, heat treatment requirements, and heat treatment techniques adopted, identifying the causes can be very challenging.
Both types of steel belong to the same category of high chromium lepidolite steel, which has a tendency to crack in cold conditions. The heat treatment technique required for this steel is also complex.
Based on my experience, the following heat treatment techniques can be used:
To obtain thermal hardness and high wear resistance, the steel can be quenched at 950-1000°C and oil cooled, resulting in an HRC>58. For best results, the quenching temperature can be increased to 1115-1130°C, followed by cooling the oil.
For thin and thin molds, air cooling can be used, and to reduce deformation, saline cooling at a temperature between 400-450℃ is recommended.
Tempering should not be done below 300-375°C, as this may reduce the toughness of the tool and cause temper brittleness. It is important to season immediately after tempering.
If quenching is done at a temperature above 1100°C, tempering two to three times below 520°C is recommended.
It is essential to note that high quenching temperatures can cause decarbonization. Therefore, it is advisable to carry out thermal pretreatment (spheroidizing annealing) before quenching.
How to distinguish heat-treated parts from non-heat-treated parts?
Additional:
“The worker accidentally mixed an unheated blank with a batch of well heat-treated parts. Both were subjected to inferior blasting treatment, making it impossible to differentiate them by color. Furthermore, their hardness is in the range of HRC35-45, making it difficult to distinguish them based on hardness as well. So how can we tell them apart? Please do not suggest cutting the part to observe the metallographic structure, as this would damage the product.”
Answers:
If you cannot identify the hardness or oxidizing colors from heat treatment, I suggest you identify them by playing the sound.
The metallographic structure of a casting and a part after quenching and tempering is different. There is also a difference in internal consumption, which can be determined by the sound tone.
What does overheating mean in heat treatment?
If the specified heating temperature is exceeded, the grain will swell and various mechanical properties will deteriorate, such as increased brittleness, decreased toughness, easy deformation and cracking.
To avoid overheating, it is essential to control the heating temperature.
If the steel is too burnt, it cannot be fixed by heat treatment or machining.
Causes and preventive measures to eliminate cracks in molds?
Causes:
- There is severe carbide segregation in the mold materials, which can cause several problems.
- Mechanical machining or cold plastic deformation stress may affect mold performance.
- Improper heat treatment, such as heating or cooling too quickly, using an inappropriate quench cooling medium, setting the cooling temperature too low, or cooling time being too long, can cause problems.
- Complex molds, irregular thicknesses, sharp angles and tapped holes can result in excessive thermal and structural stress.
- Mold quench heating temperature that is too high may cause overheating or excessive burning.
- Inadequate or premature tempering after quenching can also affect mold performance.
- Heating the mold again without intermediate annealing after quenching may be harmful.
- Inadequate grinding processes during heat treatment can also cause problems.
- Electrospark machining after heat treatment can create high tensile stress and microcracks in the hardened layer.
Preventive measures:
- Strict quality control of mold materials is essential.
- Improvement of spheroidized forging and annealing technology is necessary to eliminate reticular, banded and chain carbides and to improve the uniformity of spheroidized fabric.
- After cold machining or plastic deformation, the mold must undergo anti-stress annealing (>600°C) before tempering.
- For complicated molds, asbestos should be used to cover the threaded hole, join the dangerous sections and thin walls, and graduated quenching or isothermal quenching should be adopted.
- High temperature annealing or tempering is necessary when repairing or renewing the mold.
- The mold must be preheated before quenching, precooled during quenching, and a suitable quenching medium must be selected.
- The tempering temperature and heating time must be strictly controlled to avoid mold overheating and burning.
- The mold must be tempered in a timely manner after tempering, and the heat preservation time must be sufficient. Complex high alloy molds must be tempered 2 to 3 times.
- Choosing the right grinding technique and grinding wheel is crucial.
- It is necessary to improve the electric spark machining technique and carry out anti-stress tempering.
How to heat large stamping dies, especially for edge cutting dies?
For heat treatment of molds, it is recommended to opt for vacuum heat treatment to minimize deformation.
To facilitate heat treatment, the molds can be divided into small pieces and slow cutting must be used to ensure high precision, good finishing and minimum deformation. If clearance is guaranteed, burrs will be insignificant. It is advisable to check the accuracy of the device used.
Furthermore, it is possible that the strength of the convex mold is not sufficient. There may also be residual stress in the metal sheet after heat treatment, resulting in deformation during wire cutting. To mitigate this, it is suggested to consider pre-milling with large wire cutting holes, followed by reheat treatment, leaving a margin of 3-4mm.
Causes and prevention of weak spots on the mold surface?
Causes:
The mold surface has an oxidized layer, rust stains and partial decarbonization before heat treatment.
If the quenching medium is not chosen correctly, or if there is excess or aging impurities in the quenching medium, it may cause problems after the mold has been tempered and heated.
Preventive measures:
Before heat treatment, it is important to remove any oxide film and rust stains. Furthermore, it is crucial to adequately protect the die surface during quenching and heating. For heating, it is recommended to use an electric vacuum oven, salt bath oven or protective atmosphere oven.
During the quenching and heating process, it is important to choose the appropriate cooling medium. If the cooling medium is used for an extended period, it must be filtered or replaced regularly.
Bad structure before heat treatment?
Causes:
The original structure of matrix steel materials often exhibits severe carbide segregation.
This can be attributed to poor forging technology, such as the use of high heating temperatures, limited deformation, high forging stop temperatures and low cooling speeds, which make the elimination of reticular, banded and chain carbides difficult. spheroidizing annealing.
Furthermore, poor spheroid annealing technology, such as excessively high or low annealing temperatures, or inadequate isothermal annealing time, can lead to irregular or poor spheroidization.
Preventive measures:
When selecting mold steel material, it is important to consider the mold working conditions, production quantity, and the strength and toughness of the material. It is recommended to choose high-quality mold steel material to ensure optimal performance.
To improve the forging process, it may be necessary to adopt normalizing preparation heat treatment, which can help eliminate any non-uniformity of lattice and chain carbides and carbides in the raw materials. In cases where high-carbon matrix steel exhibits severe carbide segregation that cannot be forged, solid solution refining can be used as a treatment method.
In order to achieve the desired spheroidized annealing process for forged billets, it is necessary to formulate correct process specifications based on quenching and quenching heat treatment and fast and uniform spheroidizing annealing technique.
In addition, it is important to ensure the uniformity of billet temperature in the furnace by implementing reasonable furnace installation.
After quenching, the mold structure is large, which will cause the mold to fracture when used, which will seriously affect the service life of the mold
Causes:
Mixing the mold steel is a common mistake. The quenching temperature required for mold material is much lower than that of real steel (for example, GCr15 steel should not be treated like 3Cr2W8V steel).
Inadequate spheroidization before quenching is one of the main causes of poor spheroidization in mold steel.
Both excessively high mold quenching heating temperature and prolonged heat preservation time can cause problems.
Improper placement of the mold in the oven may result in overheating near the electrode or heating unit.
Molds with a significant change in cross section require proper selection of quenching and heating process parameters to avoid overheating in the thin section and acute angle.
Preventive measures:
A strict inspection must be carried out on the steel before entering the warehouse to avoid mixing and disorder.
Before quenching, it is important to perform correct forging and spheroidization annealing to ensure good spheroidization.
To ensure proper quenching and heating of the mold, process specifications must be followed correctly, and the quenching heating temperature and heat preservation time must be strictly controlled.
Regular thermometer checks and corrections should be made to ensure the instrument is working properly.
When heating the mold in the oven, it must be kept at a suitable distance from the electrode or heating unit.
How to heat treat Cr12MoV steel to make cold mold?
High hardness, high wear resistance and high toughness optimization treatment:
- quenching 980 ~ 1200 ℃;
- Oil quenching (machine oil)
- Quenching at 400°C for one time
- Quenching at 240°C for one time
- HRC57~61
What is the reason for the cracking of H13 matrix steel after heat treatment (quenching temperature 1100 ℃, oil cooling)?
Metallographic analysis can be performed to determine whether there is any decarbonization on the surface of materials. Decarbonization is a common cause of cracking.
H13 is a commonly used material for extrusion dies, and the hardness requirement for this material is not very high.
I recommend trying heat treatment in the temperature range of 1030-1050°C.
What material is normally used for mold guide column and guide sleeve? What type of heat treatment should be adopted and what type of performance should be achieved?
- Use #45 carbon structural steel or carbon tool steel. The hardness of heat treatment quenching is around HRC45, lower than HRC58~62. It breaks easily even with high hardness.
- Generally speaking, SKD61 or SKD11 will be used for high requirements. The quenching hardness of heat-treated H13 steel is around HRC51.
What are the uses of heat treatment in mold making?
Role of heat treatment in mold making:
- Increase hardness and wear resistance, thus improving its useful life;
- The strength is strengthened and the deformation is reduced to ensure the precision accuracy and stability of the mold.
Analysis of the causes of mold failure
Most mold failures are caused by fracture, wear and deformation, the main reasons being inadequate heat treatment and poor machining of the mold. Therefore, carefully selecting materials, correctly formulating the heat treatment process, and improving the quality of heat treatment are crucial to prolonging the life of the mold.
Mold heat treatment comprises preheating treatment and final heat treatment, with the ultimate objective of obtaining good surface quality, strength, plasticity and toughness in the mold.
The reasons for the falling of Cr12mov matrix steel parts by pieces after heat treatment
Possible Causes:
During quenching, if the temperature exceeds the recommended limit, it may lead to overheating, resulting in various problems such as coarse grains, severe decarbonization, large martensite, coarse grain fracture, low toughness and reduced plasticity.
High heating temperature and prolonged heat preservation time can also cause severe decarbonization of the material surface, coarse grain structure, weak bonding strength and significant reduction in plasticity. Therefore, it is essential to maintain proper temperature and time during the tempering process to avoid such problems.
Suggestions:
- Check heating equipment;
- Adjust the temperature and quenching and tempering time;
- Conduct heat treatment process testing for sample and conduct required performance test analysis.
Advantages of heat treatment in a salt bath?
Benefits:
- Uniform heating, small deformation
- A small amount of decarbonization without oxidation
- Rapid heating can quickly transform the internal structure of the workpiece
- Good thermal insulation and heating uniformity
- Can be heated by solid solution treatment
- Wide applicability
- Able to perform approximately oxidation-free delivery handling
Disadvantages:
- The working environment is poor and the workpiece is corroded to a certain extent
- The service life is relatively short
- The working space is small and the power is large
- Residual salt pollutes the environment
What method is used to check the effect of heat treatment?
- Just check the surface hardness
- Check the depth of the hardened layer, the hardness of the center, the structure degree of the hardened metallography and the structure degree of the tempered metallography.
The critical hardness value of the hardened depth = minimum hardened hardness × 0.8。
What is the role of deep cooling treatment of mold material?
Deep cooling treatment is the continuation of the cooling process of the part after quenching.
Application in mold industry is mainly in cold mold steel, high speed steel, bearing steel, cold mold and mold accessories
Deep cooling will change some related mechanical properties. The main functions are as follows:
- Improve the hardness and strength of the workpiece
- Ensure the dimensional accuracy of the workpiece to improve the wear resistance of the workpiece
- Improve the impact resistance of the workpiece
- Improve the internal stress distribution of the workpiece
- Increase fatigue resistance
- Improve the corrosion resistance of the workpiece
What are the reasons for the explosion of Cr12MoV heat treatment?
- Is the cooling medium cooling too quickly (cannot use salt water, pure water, etc.)?
- Before quenching, it may not be annealed properly, which results in excessive internal stress
- Poor material metallurgy (non-metallic inclusion, banded structure, eutectic carbide)
- During quenching, the oven temperature increases very quickly
- Unsuitable temperament
What is strengthening without heat treatment?
Surface treatment:
As hard chrome plating to increase the wear resistance of parts.
Shot peening reinforcement:
The fatigue strength of parts can be greatly improved under alternating stresses.
Rolling:
The rolling tool is used to apply pressure to the surface of metal parts at room temperature. This causes plastic deformation and modifies the microgeometric shape of the metal surface. By doing so, the surface smoothness, fatigue resistance, wear resistance and hardness of parts are improved.
