Container heat treatment

There are no standards for heat treatment. What you need to pay attention to is the heating and cooling speed, time, and holding time. The temperature inside the furnace when entering and exiting, etc.

There are several points to pay attention to: 1. Inlet and outlet temperature, material heat treatment process requirements. (sensitive temperature/purpose of heat treatment, etc.) 2. Cooling and heating speed/holding time, etc. 3. Material strength at heat treatment temperature, anti-deformation treatment, etc.

1. Preheating and heating rate; 2. Holding time; 3. Cooling rate.

No welding operations are allowed after heat treatment is completed

　The heat treatment process can be prepared according to the requirements of post-weld heat treatment in Chapter 8 of JB/T4709-2000 Steel Pressure Vessel Welding Regulations.

The main ones are the thermal process curve entering the furnace temperature, heating rate, heat treatment temperature, holding time, cooling rate, and exit temperature. See page 90 of the 99th edition of the Code of Conduct.

There are parameters in JB4709. You can check the corresponding content. Does anyone have a heat treatment process that can be used as a reference?

"The fuel gas liquid separation tank is a first-class container. Why is it required to undergo overall stress relief heat treatment? Is there hydrogen sulfide in the medium?

Fuel gas contains products from the refining of heavy oil, including everything. There should be a reason for the design institute to require heat treatment.

Also, attention should be paid to protecting the sealing surface during heat treatment. If the equipment has a welding test plate, it should be heat treated with the furnace.

First of all, you need to determine what material it is made of before you can determine the heat treatment process. Unlike the overall stress relief heat treatment, it must be entered into the furnace as a whole. Generally, there are oil heating, electric heating, etc. The whole thing can be wrapped with insulation cotton and heat treated outdoors.

Did the other party ask for a hardness after heat treatment? This should be required. Different materials use different heat treatment temperatures, and the final hardness standards are also different.

To prepare a heat treatment temperature rise curve chart, the main contents are as follows: Requirements: 1. Before heat treatment, apply high-temperature paint to protect each flange surface and thread. 2. Furnace temperature ≤ ℃, heating rate ℃/H, holding at ℃ furnace temperature for minutes, cooling in the form, cooling rate ℃/H 3. Welding test plates are heat treated in the same furnace. 4. After the heat treatment is completed, a heat treatment report including the temperature-time control curve will be issued.

Thanks, I want to solve the same problem :)

(Transfer) Heat treatment residual stress refers to the final residual stress of the workpiece after heat treatment, which has an extremely important impact on the shape, size and performance of the workpiece. When it exceeds the yield strength of the material, it will cause deformation of the workpiece. When it exceeds the strength limit of the material, it will cause the workpiece to crack. This is its harmful side and should be reduced and eliminated. However, by controlling the stress to make it reasonably distributed under certain conditions, the mechanical properties and service life of the parts can be improved, turning disadvantages into advantages. Analyzing the distribution and change patterns of stress during the heat treatment of steel and making it reasonably distributed has far-reaching practical significance for improving product quality. For example, the impact of reasonable distribution of surface residual compressive stress on the service life of parts has attracted widespread attention. 1. Heat treatment stress of steel During the heating and cooling process of the workpiece, due to the inconsistent cooling speed and time between the surface layer and the core, a temperature difference is formed, which will lead to uneven volume expansion and contraction and generate stress, that is, thermal stress. Under the action of thermal stress, since the initial temperature of the surface layer is lower than that of the core, the shrinkage is also greater than that of the core, causing the core to be stretched. When cooling is completed, the final cooling volume shrinkage of the core cannot proceed freely, causing the surface to be compressed and the core to be stretched. That is, under the action of thermal stress, the surface layer of the workpiece is eventually compressed and the core is stretched. This phenomenon is affected by factors such as cooling rate, material composition and heat treatment process. When the cooling rate is faster and the carbon content and alloy composition are higher, the uneven plastic deformation generated under the action of thermal stress during the cooling process is larger, and the final residual stress is larger. On the other hand, due to the structural change of steel during the heat treatment process, that is, when austenite transforms into martensite, the increase in specific volume will be accompanied by the expansion of the workpiece volume, and various parts of the workpiece will undergo phase transformation, resulting in inconsistent volume growth and tissue stress. The final result of tissue stress changes is that the surface layer is subject to tensile stress and the core is subject to compressive stress, which is exactly the opposite of thermal stress. The size of the structural stress is related to the cooling rate, shape, chemical composition of the material and other factors of the workpiece in the martensitic transformation zone. Practice has proved that during the heat treatment of any workpiece, as long as there is a phase change, thermal stress and tissue stress will occur. It’s just that thermal stress has already been generated before the tissue transformation, while tissue stress is generated during the tissue transformation process. During the entire cooling process, the result of the combined effect of thermal stress and tissue stress is the actual stress in the workpiece. The result of the combined action of these two stresses is very complex and is affected by many factors, such as composition, shape, heat treatment process, etc. As far as its development process is concerned, there are only two types, namely thermal stress and tissue stress. When the directions of action are opposite, they cancel each other, and when the directions of action are the same, they superimpose each other. Whether they cancel each other out or superimpose each other, the two stresses should have one dominant factor. When thermal stress dominates, the result is that the center of the workpiece is stretched and the surface is compressed. When tissue stress dominates, the result is tension on the compressed surface at the center of the workpiece. 2. The influence of heat treatment stress on quenching cracks. Factors (including metallurgical defects) that can cause stress concentration in different parts of the quenched parts can promote the occurrence of quenching cracks, but they will only appear in the tensile stress field (especially under the maximum tensile stress). If there is no cracking effect in the compressive stress field. The quenching cooling rate is an important factor that can affect the quenching quality and determine the residual stress. It is also a factor that can have an important or even decisive impact on quenching cracks. In order to achieve the purpose of quenching, it is usually necessary to accelerate the cooling rate of the part in the high temperature section and make it exceed the critical quenching cooling rate of the steel to obtain the martensite structure. As far as residual stress is concerned, this can increase the value of thermal stress that offsets the effect of tissue stress, so it can reduce the tensile stress on the surface of the workpiece and achieve the purpose of inhibiting longitudinal cracking. Its effect will increase with the speed of high temperature cooling. Moreover, if the workpiece can be hardened, the larger the cross-sectional size of the workpiece, although the actual cooling rate is slower, the risk of cracking will be greater. All this is due to the fact that the thermal stress of this type of steel actually slows down the cooling rate with the increase in size, the thermal stress decreases, and the organizational stress increases with the increase in size. Finally, tensile stress, dominated by organizational stress, acts on the surface of the workpiece. And it is quite different from the traditional concept that the slower the cooling, the smaller the stress. For this type of steel parts, only longitudinal cracks can form in high-hardenability steel parts quenched under normal conditions. A good principle to avoid quenching cracks is to try to minimize the anisochrony of martensitic transformation inside and outside the section. Merely implementing slow cooling in the martensitic transformation zone is not enough to prevent the formation of longitudinal cracks. Under normal circumstances, arc cracks can only occur in non-hardenable parts. Although the overall rapid cooling is the necessary formation condition, the real cause of its formation is not the rapid cooling (including the martensitic transformation zone) itself, but the local position of the quenched part (determined by the geometric structure). The cooling rate in the high-temperature critical temperature zone is significantly slowed down, so it is not caused by hardening. Transverse and longitudinal splitting in large non-hardenable parts are caused by the residual tensile stress with thermal stress as the main component acting on the center of the quenched part. At the center of the unhardened section of the quenched part, cracks first form and expand from the inside out. In order to avoid such cracks, a water-oil double liquid quenching process is often used. The purpose of implementing rapid cooling in the high-temperature section in this process is only to ensure that the outer layer metal obtains a martensitic structure. ； From the perspective of internal stress, rapid cooling at this time is harmful rather than helpful. Secondly, the purpose of slow cooling in the later stage of cooling is not mainly to reduce the expansion rate and structural stress value of martensitic transformation, but to minimize the cross-section temperature difference and the shrinkage rate of the metal in the center of the section, so as to reduce the stress value and ultimately inhibit quenching cracking.

There are also some introductions in the regulations, you can refer to them.