In view of some problems, including heat treatment itself, or other industries to heat treatment understanding, summed up this proposition, the whole article system is not very strong, inappropriate, please correct.

1. Does vacuum heating have quenching carburization?
In the analysis of vacuum heat treatment workpiece carburization phenomenon, there are two misunderstandings: first, think that the workpiece is carburized in quenching oil; Second, it is thought that the graphite parts of the heating chamber cause carburization. In fact, in many cases, it is not the two reasons, but the cleanliness of the heating chamber is not high, a large number of quenching oil in the workpiece into the oven, basket pollution, feeding car in and out of the hot chamber, residual in the cold wall of the hot chamber, heating to form a volatile reduction atmosphere, carburizing the workpiece.

In addition to the temperature above 1050℃ directly into the oil. When the workpiece oil is heated below 1050℃, the obvious carburization phenomenon will not be formed when the oil is slightly pre-cooled.

The graphite parts of the heating chamber can not be excluded from the carburization of the workpiece, but there is no residual quenching atmosphere.

The carburization phenomenon of vacuum heating quenching is more serious because of the pollution of the furnace from quenching oil, not what people say is the reason of quenching or graphite parts in oil!

2. Small deformation of vacuum heat treatment (quenching)?
There are two concepts in heat treatment deformation: microstructure deformation and shape structure deformation. The results show that vacuum heat treatment has the smallest deformation when the same microstructure and hardness are obtained. That is, minimum tissue deformation.

For shape and structure deformation, vacuum heat treatment is often not as small as other furnace heat treatment deformation, other furnace heat treatment, such as quenching, it is easy to use classification, isothermal, furnace straightening and other methods to control the amount of deformation, vacuum quenching due to the imperfection of these functions, sometimes will increase.

The confusion of these two concepts gives people the impression that vacuum heat treatment deformation is small, which is wrong or incomplete understanding!
3. Is ignition color related to temperature?
After tempering the surface of the steel takes on a color of oxide film, called tempering color. In many cases, the tempering temperature needs to be determined according to the tempering color. Tempering color changes with temperature, so the tempering temperature can be roughly determined according to the tempering color. But the temper color is also related to the temper time, usually with 5 minutes of time.

The tempering color of carbon steel at different temperatures is determined by 5 minutes. The surface color is as follows:
Light yellow: 200℃;
Grass yellow: 220℃;
Brown: 240℃;
Purple: 260℃;
Blue purple: 280℃;
Dark blue: 290℃;
Blue: 300℃;
Light blue: 320℃;
Blue gray: 350℃;
Gray: 400℃.

Stainless steel at different temperatures of the color:
Light wheat yellow: 290℃;
Wheat yellow color: 340℃;
Reddish brown: 390℃;
Light red: 450℃;
Light blue: 530℃;
Deep blue: 600℃.

Tempering color of low alloy steel at different temperatures:
Light wheat yellow: 225℃;
Wheat yellow color: 235℃;
Reddish brown: 265℃;
Light red color: 280℃;
Light blue: 290℃;
Deep Blue: 315℃.

However, in many materials, the relationship between color and temperature is only mentioned, ignoring the key premise of time. Under the same temperature, with the extension of holding time, the final color will be biased to a higher temperature color. Often resulting in a miscalculation of the actual temperature.

4. What is the high proportion of die failure heat treatment?
Statistical data of early die failure causes at home and abroad:

Failure cause Statistics of Japan % Statistics of Shanghai %
Mold material quality is not good 7 17.8
Mold design is not reasonable 10 3.3
Improper heat treatment process 44 52
Mold processing method is not good 7 8.9
Lack of knowledge of mold material properties 5 ----
Improper cutting of mold material 3 ----
Improper choice of mold material 3 ----
Mold service condition is not good 7 11
The forging process is improper ---- 7
In other respects 14 ----

This list of data shows the results of past accidents and is not applicable to predicting future accidents. That is to say, for the reason of a mold failure tomorrow, it can not be considered that the cause of mold failure is heat treatment accounting for 44 ~ 52%. It's about doing specific analysis. This statistical data misleads many people, so that people form a thinking set: that mold failure is the problem of heat treatment. I hope you will pay attention to this problem.

5. My forging size is qualified, and the quality of heat treatment has nothing to do with my forging?
Forging process is to eliminate material defects, improve the structure, improve the material properties. Save the amount of mechanical cutting, improve the utilization rate of materials. But today's forgers forget all about "eliminating material defects and improving organizational form", and only "work hard" to ensure forging size, ignoring the requirements of improving material properties. What is more amazing is that some materials through the forging process, not to improve the material properties, but to destroy the material properties. The forging waste heat annealing method is used indiscriminately, resulting in the formation of serious network carbide structure in the material.
Because the heating temperature of the material forging is much higher than that of the heat treatment quenching, the tissue inheritance of the "serious network carbide structure" will bring serious consequences to the product quality.

6. My heat treatment hardness is qualified, so the early failure of your product has nothing to do with my heat treatment?
Heat treatment should not only ensure qualified hardness value, but also pay attention to process selection and process control. Superheated quenching and tempering can reach the required hardness; Similarly, quenching underheat, by adjusting the tempering temperature, can also be made to the required hardness range. There are many people who do this. Some in order to save electricity consumption, underheat quenching; Some are underheated quenching due to the limit temperature of the heating furnace. How is the early failure of such a heat-treated product unrelated to heat treatment?

7. When I entrusted you with heat treatment, my products were good, but you messed up the heat treatment, will you be responsible for compensation?
This kind of statement in the treatment of heat treatment quality problems, will often encounter, after hearing this statement, heat treatment people really laugh and cry. If you have such a customer, the problem must be the customer, not the heat treatment! Because customers have no understanding of manufacturing quality process control before heat treatment, they do not consider creating a good pretreatment state for heat treatment.

8. The manual says that heat treatment and quenching can reach this hardness, why can't you do this hardness?
Some people think that the hardness of his design is selected according to the hardness range in the manual, how can you say that the heat treatment can not reach this hardness?

For example: with spring 60Si2Mn to make large parts, due to the actual workpiece thickness is very large, significant thickness, heat treatment has no good way to reach the required hardness standards. According to the manual, the hardness can reach: 58 -- 60HRC. There is no way to achieve this in combination with actual artifacts. Can only reduce the heat treatment requirements.

Determining the hardness of heat treatment is controlled by the following factors: material grade, mold size, workpiece weight, shape and structure, and subsequent processing methods. After heat treatment of the die, the internal and external hardness are not the same, and the material and design size should be selected according to the size of the die, not directly in accordance with the technical standards and hardness requirements in the design manual. The hardness standards on the manual are the heat treatment results from small samples, and the reasonable hardness indicators must be determined according to the actual situation when applied to the real thing. Unreasonable hardness index, such as too high hardness, will lose the toughness of the workpiece, resulting in the use of the workpiece cracking.

9. This product is heat treated by you. If there is a problem in my use, are you responsible for heat treatment?
When an enterprise breaks and injures the operator in the process of using the mold, the enterprise immediately informs the heat treatment manufacturer: If someone is hurt in the use of the mold of your heat treatment, how much should you compensate? When I asked the reason, I got the reply that this product was processed by your heat treatment, and there was an accident, so I ask you to compensate. Look what a good reason!
Product failure should be analyzed from the aspects of design, material selection, material defects, process defects (including heat treatment), assembly and use to find out the real reason. It is unreasonable to assume that the failure is caused by heat treatment in order to shirk responsibility. I think it is the same reason why doctors must see patients in person when seeing a doctor. It is the same reason why we should make a comprehensive analysis of product failure in waste design, material selection, material defects, process defects (including heat treatment), assembly and use process, etc. We can not directly identify which link is wrong!

The matter was later assessed by the most authoritative institutions, and the quality of the heat treatment was completely normal, which was not the cause of the accident. The real cause is a usage problem ----- overload!

A lack of knowledge about an industry is understandable, but the problem is either handled with a scientific attitude or ignorance.
I'm glad to be engaged in heat treatment. Why? You see that heat treatment has been able to "cure all diseases", what things are looking for heat treatment ah!

10. The heat treatment hardness of my product can only be 60HRC. I can't accept 59 or 61HRC?
Often encountered commissioned heat treatment products hardness value can only be in a certain value, there can be no deviation! For example, if the hardness of heat treatment is required to reach 60HRC, then 59HRC, or 61HRC after heat treatment will be considered as nonconforming product. As everyone knows, the allowable deviation of Rockwell hardness machine is 1HRC! You explain heat treatment to him, he (she) will put on a "face of God" : do you want to do my heat treatment products? Market competition! Heat treatment manufacturers had to bear the scalp to undertake, as for heat treatment manufacturers how to do? I'm sure my peers will be able to guess!
It is really "how bold people, how much production."

11. Quenched workpiece is not cold to room temperature, can not be tempered?
Some people think that after quenching, has not cooled to room temperature, can not enter the tempering process. In fact, many kinds of steel, especially low and medium carbon steel, the martensitic transformation end point is mostly higher than room temperature, cold to room temperature, but easy to crack, quenching out can be as soon as possible into the tempering process.

12 quenching out of the workpiece must be tempered with temperature?
This practice is not desirable, according to the martensitic transition point of steel to determine the furnace temperature after quenching before tempering! In order to prevent quenching cracking, can not speculate, generalize the use of tempering method with temperature!

13. Can you heat treat and quench my products after they are annealed and placed for a week?
Some bosses claim to have the secret of improving the service life of molds! What is his secret? To explore what it is, it is required that the heat treatment after annealing treatment, not immediately quenching and tempering treatment. The mold must be left at room temperature for a week between annealing and quenching! Say: release annealing stress! I wonder if the expert can answer this question? !
What a wonderful world!

14. The size processing of the product has been completed, and the heat treatment is required to ensure no deformation?
Some people in order to save the cost of product processing, before the heat treatment, all the dimensions of the processing end, and then to the heat treatment quenching and tempering. The heat treatment is required to ensure that there is no deformation in the heat treatment process, or only allow the amount of deformation within the tolerance zone of the last cold work! The process of heat treatment is essentially a stage of tissue deformation, the accumulation of deformation at the micro level, who can guarantee that it will not be shown as dimensional deformation at the macro level?
In order to save his own expense, he passed the problem on to the heat treaters. Aren't these people "smart"? !

15. Does the heat-treated product have no hardness?
Many enterprises that entrust products to be processed outside have learned to require incoming inspection. Since the leaders put forward this requirement, they will treat it seriously and buy a Rockwell hardness tester back, put it in the factory, and begin incoming inspection of the products after heat treatment. These should be reasonable, but they always fail to pass the test of heat treatment products! That's a lot of work for the heat treatment company. Why? Clearly is passed the inspection factory, how to the user's hands is not qualified? The company couldn't figure it out.

The heat treatment company takes it seriously and urgently dispatches staff to deal with this matter! Really do not see do not know, a look startled! They did not remove the decarbonized layer of heat treatment products (processing allowance is enough to ensure that after processing, no residual decarbonized layer), directly on the surface of the workpiece hit HRC hardness! How can this be so hard? My god!  So who doesn't trust who?

16. Heat treatment engineering good iron carbon balance phase diagram is OK? In many materials that iron carbon balance phase diagram in heat treatment is very important knowledge, is the basis for the development of iron and steel materials heating technology, and pointed out: especially heat treatment workers must master iron carbon balance phase diagram.

The Fe-C phase diagram is the microstructure diagram of Fe-C alloy in equilibrium state, rather than the transformation diagram of non-equilibrium martensite, bainite and other structures. The critical temperature parameters of iron-carbon phase diagrams are limited only to carbon steel and cast iron, unalloyed steel and alloy cast iron. The equilibrium diagram of alloy steel and alloy cast iron differs greatly from the equilibrium diagram of iron carbon due to the addition of other alloying elements.

The iron carbon equilibrium phase diagram is the result of the speed in the heating and cooling process is extremely slow, and it is limited to the iron carbon alloy steel. This theoretical state is impossible to be widely used in the actual production. The actual microstructure transformation in the heating and cooling process of quenching and other heat treatment is carried out at a certain heating speed and cooling speed, not completely reach the equilibrium state. Therefore, iron-carbon equilibrium phase diagram is only the necessary basic knowledge and starting point for studying heat treatment, rather than the phase diagram directly used in the process of heat treatment.

Heat treatment workers who have mastered the knowledge of iron carbon balance phase diagram is only the beginning of heat treatment learning and can not reach the realm of using iron carbon balance phase diagram to deal with the practical problems of the process.