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24 questions and answers about die heat treatment
Nov 30, 2017

24 questions and answers about die heat treatment

1, H13 die steel heat treatment hardness can reach 58 ℃?

2, 1050 ~ 1100 ℃ heating quenching, oil quenching, can meet the requirements, but the general hot die is not required for such a high hardness, so high hardness performance will be poor, not easy to use, generally in HRC46 ~ 50 performance Good, durable.

2, after the surface of the mold heat treatment what white wash?

Question added: I was to open a mold polishing shop, the general mold are used to fight the stone and then to nitriding, nitriding again with oil stone that layer of black rubbed white, then polish a lot of trouble, do not rub white No appearance, the material H13, a variety of imports, if there is syrup to wash the white, you can directly polished.

(1) can be stainless steel pickling solution, or hydrochloric acid cleaning. Sand blasting is also acceptable. Grinding grinding machine, then the high cost, and processing large, it is possible to make the size of non-compliance. Hydrochloric acid can not afford to wash, it is estimated that you are using high chromium die steel? D2 or H13? High chromium steel mold oxide layer is more difficult to wash away. With stainless steel pickling should be able to, abrasive shops or stainless steel stores have sold.

(2) (2) Do you have no stainless steel pickling cream? That kind of can. H13 such high chromium steel mold, the oxide layer is difficult to wash off with hydrochloric acid. There is another way, I myself also use. Since your mold has been whetstone, the surface is relatively smooth. In fact, you can only use coarse whetstone first grinding, or grinding belt, then go to heat treatment. Back with fine oil stone polished. And I use the method is to use fiber wheel first polished, you can effectively remove the black skin, then grinding and polishing. Or sandblasting, with 800 mesh boron carbide sandblasting try again, it should be able to remove the black skin, do not need too much effort to reground.

3, heat treatment plant on the metal is how to heat treatment?

Heat treatment plant equipment is very much, the furnace is about box furnace, pit furnace, box furnace with the most, many heat treatment can be dealt with here, such as annealing, normalizing and quenching heating process, tempering these common Heat treatment.

In fact, it is an electrically heated furnace, the furnace is first heated to a predetermined temperature, then the workpiece is thrown in, waiting for a period of time to a predetermined temperature, and then incubated for a period of time, and then removed, or cooled together in the furnace, pit furnace is generally As a carburizing equipment, it is an underground furnace. After the work piece is put in, it is sealed, and then some carbon-rich liquid, such as kerosene or methanol, is dripped into the furnace, and then the liquid is decomposed into carbon atoms to penetrate into the work piece under high temperature surface.

Quenching the pool is quenching the place, is a pool, which has an aqueous solution or oil, is the box furnace out of the workpiece cooling quenching, is generally thrown directly into, and then wait for a while to remove. There are other devices, such as a high-frequency machine, a very powerful device that turns 50 Hz power into a 200 kHz current, such as the common 200 kW maximum and then an internal cooling Copper coils made of water on the outside of the workpiece, the general tens of millimeters of the workpiece, a few seconds to ten seconds when you see the workpiece surface turns red, the surface temperature to a predetermined value, then there is a water Set up to spray quenching liquid to the workpiece surface to complete the quenching process. Common to these.

4, our recent Cr12 or Cr12MoV material heat treatment and cracked a few times, and why?

The best metal mold parts size, shape and heat treatment requirements, and you take the heat treatment process curve to tell, otherwise hard to say. These two types of steel are a class, is a high-carbon high-chrome ledeburite steel itself has a tendency to cold cracking. Heat treatment process is also more complicated.

Below in the absence of the above information talk about my experience: 950-1000C quenching, oil cooling, HRC> 58. In order to obtain the hot hardness and high wear resistance, quenching temperature increased to 1115-1130C, oil cooling. Thin air-cooled, in order to reduce the deformation of 400-450C salt liquid cooling. Do not tempering at 300-375C, will reduce the tool's toughness, temper brittleness, the other tempering immediately after quenching. Higher than 1100C quenched, tempered at 520C 2-3 times. Please note that the quenching temperature is too high there will be decarburization tendency, this can be pre-heat treatment before quenching - ball annealing.

5, how to distinguish between heat treatment and no heat treatment of the workpiece?

Questions added: workers accidentally put a non-heat treatment of raw materials and a batch of commissioned heat treatment of the workpiece mixed together, and now how to distinguish them, do not cut the workpiece to look at the metallographic ah, that would undermine the product, urgent With delivery? 30Cr heat treatment process by normalizing, then quenching, and then tempering, the workpiece is cast without heat treatment. Both have been shot blasting color change can not be divided, as well as the hardness is between 35-45, and can not be distinguished by the hardness.

If you can not pass the hardness and heat treatment of oxidation color to determine. I suggest you discern by tapping the sound. Casting and quenching + tempering the metallurgical work piece different, there are differences in internal friction, by tapping, you may be able to distinguish.

6, heat treatment in the burning What does it mean?

Exceeds the specified heating temperature, resulting in grain growth, the mechanical properties such as brittle become worse, toughness decreased, easy to deformation and cracking, etc., control the heating temperature can avoid over-burning. Refers to the steel in the solid-liquid phase temperature range above a certain temperature heating, the austenite grain boundary chemical composition changes, partial or entire grain boundaries appear melting phenomenon. At this time grain boundary will be enriched S, P and other compounds, leading to reduced grain boundary binding, mechanical properties deteriorated severely. After burning steel can not be remedied by heat treatment or processing methods.

7, mold quenching the causes and preventive measures?


1) there is a serious mold mesh carbide segregation.

2) Die exist in the mechanical processing or cold plastic deformation stress.

3) Die heat treatment improper operation (heating or cooling too fast, improper choice of quenching cooling medium, cooling temperature is too low, cooling time is too long, etc.).

4) Die shape complex, uneven thickness, with sharp corners and threaded holes, so that thermal stress and tissue stress is too large.

5) die quenching heating temperature is too high, overheating or over burning.

6) After quenching mold is not tempered or tempering Insufficient time.

7) Die repair quenching heating, without intermediate annealing again heated quenching.

8) Die heat treatment, grinding process improper.

9) Mold heat treatment after EDM, the hardened layer there is a high tensile stress and micro-cracks.


1) Strict control of mold the inherent quality of raw materials

2) Improve the forging and ball annealing process to eliminate the mesh, ribbon, chain carbide, to improve the uniformity of nodular organization.

3) After machining or cold deformation of the mold should be stress-relief annealing (> 600 ℃) before the heat quenching.

4) the shape of the mold should be asbestos plugging threaded holes, banding risk sections and thin-walled Department, and the use of graded or isothermal quenching.

5) Rework or refurbished molds need to be annealed or tempered at high temperature.

6) The mold should be preheated in the quenching heating, cooling precooling measures taken, and select the appropriate quenching medium.

7) should be strictly controlled quenching temperature and time to prevent mold overheating and over burning.

8) After quenching the mold should be promptly tempered, holding time should be sufficient, high alloy complex mold should be tempered 2-3 times.

9) Select the correct grinding process and the appropriate grinding wheel.

10) Die EDM process improvement, and to stress tempering.

8, how to conduct large-scale stamping die heat treatment? In particular, trimming these molds often produce glitches, can not operate normally.

(1) mold heat treatment Select vacuum heat treatment, to obtain the minimum deformation.

(2) the mold can be spliced structure, divided into small pieces like heat treatment. The best slow wire cut, high precision, high finish, small deformation. The gap is guaranteed, the burr will be small. Look at your equipment accuracy is poor.

(3) cutting edge burr In addition to the above mentioned a few, I think the punch unilateral stress, the intensity is not enough possibility. Is the punch too thin? Whether to design by knife? There are sheet metal residual stress after heat treatment, the wire will be deformed after cutting, you can consider the larger wire cut hole pre-milling heat treatment, leaving 3 ~ 4mm line cutting.

9, I use H13 steel to do hot extrusion die Forging the workpiece is brass heat treatment for 45 ~ 48 ° die diameter 120mm, high 70mm, working hours after the mold cracking?

(1) forging temperature is about 900 ~ 1000 ℃? Is the temperature too high? Mold before use without adequate preheating may also be easy to crack. Mold design may also be easy to crack unreasonable. Tempering the mold temperature will increase some, narrow the gap between the actual forging temperature, tempering actually longer.

(2) This should be considered comprehensively, when necessary, to do under the metallographic, in order to determine the basic reasons for Oh.

10, the mold surface has a soft point causes and prevention?


1) Die in the heat treatment before the surface oxide, rust and local decarburization.

2) Die quenching heating, cooling quenching medium improper selection, excessive quenching medium impurities or aging.


1) The mold should be removed before the heat treatment of scale, rust, quenching and heating properly protect the mold surface should be used in a vacuum furnace, salt bath furnace and the atmosphere to protect the furnace heating.

2) Die quenching after heating cooling, you should choose the right cooling medium, long-term use of cooling medium to be filtered regularly, or regularly replaced.

11, poor tissue before the heat treatment mold?


1) There is a serious carbide segregation in the original structure of die steel.

2) forging process is not good, such as forging heating temperature is too high, deformation is small, forging temperature is high, slow cooling after forging, etc., forging the organization coarse and mesh, ribbon and chain carbide existence, the ball When annealing is difficult to eliminate.

3) ball annealing process is poor, such as the annealing temperature is too high or too low, isothermal annealing time is short, etc., can lead to uneven microstructure or spheroidization poor annealing.


1) generally should be based on mold working conditions, production volume and material itself toughening performance, try to choose a good quality mold steel material.

2) Improve the forging process or use normalizing heat treatment to eliminate the inhomogeneity of the mesh and chain carbides and carbides in the raw materials.

3) can not be forged carbide carbide segregation severe high-carbon die steel can be dissolved heat treatment.

4) After forging die blanks to develop the correct ball annealing process specifications, can be quenched and tempered heat treatment and rapid ball annealing agent.

5) Reasonable loading furnace, to ensure the uniformity of temperature in the mold blank.

12, the mold after the coarse tissue hardening, the mold will be used when the fracture, a serious impact on the life of the mold?


1) Mold steel confused, the actual steel quenching temperature is far lower than the required quenching temperature of the mold material (such as GCr15 steel as 3Cr2W8V steel).

2) Die steel quenching before not the right ball treatment process, bad ball organization.

3) Die quenching heating temperature is too high or holding time is too long.

4) mold placed in the furnace in the wrong place, near the electrode or heating element prone to overheating.

5) Large changes in the cross section of the mold, quenching and heating process parameters improper selection, resulting in overheating at the thin section and sharp corners.


1) Steel warehousing should be strictly tested before, to prevent confusion and confusion of steel.

2) Die forging should be carried out before the right forging and ball annealing, to ensure a good ball organization.

3) The correct development of mold quenching heating process specifications, strict control of quenching temperature and holding time.

4) Regular testing and calibration thermometer, to ensure the normal work of the instrument.

5) When the mold is heated in the furnace, keep the proper distance from the electrode or heating element.

13, with Cr12MoV steel cold mold should be how to heat treatment?

High hardness, high wear resistance and high toughness optimization: 980 ~ 1200 ℃ heating quenching, oil quenching (oil) 400 ℃ tempering time, tempering at 240 ℃ once, HRC57 ~ 61, ultra durable durable.

14, H13 die steel after cracking what is the reason, quenching temperature is 1100 ℃, on the oil cooling?

Metallographic analysis can be carried out to see if there is material on the surface decarburization, cracking is generally caused by decarburization, H13 generally do extrusion die, the hardness of the material is not very high, you are not using a vacuum Furnace recommended 1030 ~ 1050 ℃ try.

15, the guide pin guide mold commonly used material? What kind of heat treatment, what kind of performance requirements?

(1) In the Mainland with 45 # carbon structural steel or carbon tool steel, heat treatment quenching hardness HRC45 or so, less than HRC58 ~ 62, is to that high, it is easy to break.

(2) a plate is required for high heat treatment with SKD61 or SKD11 and H13 quenching hardness HRC51 or so.

16 mold manufacturing heat treatment purposes, how to use?

Questions added: is not a template after processing heat treatment, which is the main link?

Mold manufacturing in the role of heat treatment: improve the hardness, wear resistance, thereby enhancing their life expectancy; enhanced strength, deformation reduction, to ensure the accuracy and accuracy of the mold stability.

17, mold failure analysis?

Most of the failure is caused by the fracture, wear and deformation, the main reason is the improper heat treatment and mold processing poor. Therefore, a reasonable choice of materials, the correct development of heat treatment process, improve the quality of heat treatment, to extend the service life of the mold plays a key role. Die heat treatment, including pre-heat treatment and the final heat treatment, the ultimate goal of heat treatment is to make the mold has a good surface quality and strength, ductility and toughness of a reasonable match.

18, Cr12mov die steel after heat treatment one by one out of reason?

(1) You may be in quenching, the temperature is too much, overheating, resulting in coarse grains, decarburization serious, martensite coarse, coarse fracture toughness, toughness, low plasticity.

(2) The heating temperature is too high, holding time is too long, resulting in serious decarburization of the surface of the material, coarse grains, poor binding, plastic significantly reduced.

Recommendation: Proofreading heating equipment; adjust quenching, tempering temperature and time; do the sample heat treatment process test, the necessary performance test analysis.

19, salt bath heat treatment advantages?

Advantages: uniform heat distortion, less non-oxidation decarburization, fast heating, can quickly change the internal structure of the workpiece, thermal insulation properties and uniform heating performance, can be solution heat treatment, wide applicability, can be almost no oxidation The shipping process and so on.

Disadvantages: poor working conditions, the workpiece has a certain corrosion, the service life is relatively short, the working space size and power terms, the power larger, smaller size. Waste salt and some pollution to the environment, if customers have higher requirements for non-oxidation can be considered, the cost of the general situation.

20, test the effect of heat treatment using what method?

Simply check the surface hardness. Accurate broken inspection: check the hardened layer deep, heart hardness, quenched metallurgical grade, grade metallurgical grade. Hardened layer deep critical hardness = quenching hardness minimum X0.8.

21, mold material cryogenic treatment What are the effects?

Cryogenic treatment is the continuation of the cooling process after quenching the workpiece, the application in the mold industry is mainly reflected in the case of cold work die steel and high-speed steel, bearing steel, cold work die and mold parts have cryogenic technology applications. Cryogenic will change some of the relevant mechanical properties, the main role of the following points: to enhance the hardness and strength of the workpiece to ensure the dimensional accuracy of the workpiece to improve the wear resistance of the workpiece to improve the impact toughness of the workpiece to improve the stress distribution within the workpiece to improve fatigue strength , Improve the corrosion resistance of the workpiece.

22, after cutting heat treatment is the template of the problem of cracking or heat treatment?

(1) I was engaged in heat treatment, I personally think that is the issue of heat treatment. Because there is no heat treatment of steel wire cutting is difficult to crack, wire cutting cracking because of stress concentration occurs. Therefore, heat treatment is not only necessary to achieve the hardness of the heat treatment must also eliminate the internal stress. The key to eliminate internal stress is tempering temperature and tempering time. If the tempering temperature is too low, the tempering time longer than the internal stress can not be eliminated; if the tempering temperature is too high, although the elimination of stress, but can not meet the requirements; if the tempering temperature is appropriate, but the tempering time is too short, the stress Can not be completely eliminated. Therefore, the key to heat treatment after wire cutting is tempering temperature and tempering time control.

(2) wire cutting after heat treatment cracking This situation is more complicated, there may be inadequate tempering mold quenching, there are also possible forging die defects. If it is a general carbon steel mold, tempering is not sufficient is the main reason, you need to give priority to high alloy molds, it is also possible that the material itself defects, such as impurities, carbide segregation, which require high-power metallographic examination to judgment.

23, Cr12MoV heat treatment burst what are the reasons?

(1) cooling medium is too fast cooling (can not use saline, water, etc.)

(2) before quenching, may not retreat fire, causing internal stress is too large

(3) material metallurgy is not good (non-metallic inclusions, ribbon organization, eutectic carbide)

(4) quenching, the furnace temperature rise too fast

(5) Did not temper in time

24, what is non-heat treatment to strengthen?

Surface treatment: such as hard chrome plating, increase the wear resistance of parts.

Shot peening: used to withstand alternating stress under the work of parts, can greatly improve the fatigue strength.

Rolling: the use of rolling tools at room temperature under pressure on the part surface, the metal surface plastic deformation, the metal surface to amend the micro-geometry, improve surface finish, improve part fatigue strength and wear resistance and hardness.

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