A method for forging N08810 steel plate

Abstract

The present invention discloses a N08810 steel plate forging method, which is characterized by segmented heating and jacket forging. The advantage is that the present invention reduces the temperature difference between the surface and the core of the steel ingot by segmented slow heating, reduces thermal stress, and can avoid the risk of N08810 steel ingot cracking caused by thermal stress. Diffusion annealing is used to homogenize the element segregation, and the carbides in the grain boundaries can be dissolved back into the grains, so that the carbides inside the N08810 corrosion-resistant alloy steel ingot and the element segregation are basically eliminated. In addition, the cooling process in the forging method increases the high-temperature strength of the N08810 corrosion-resistant alloy steel ingot, and prevents surface cracking during forging and blanking. In addition, the present invention can effectively inhibit the occurrence of hydrogen absorption, oxygen absorption and severe heat dissipation through jacket forging, ensuring that the mechanical properties of the plate are at a high level.

Description

Technical Field

[0001] The invention relates to the field of alloy forging, and in particular to a N08810 steel plate forging method. Background Art

[0002] N08810 corrosion-resistant alloy, also known as Alloly 800H, is an austenitic nickel-iron-chromium alloy that has undergone a special solid solution treatment. It contains elements such as carbon, aluminum, titanium, silicon, manganese, and a limited amount of (Al+Ti). The characteristic of this alloy is that it has good tensile strength at high temperatures, especially above 600°C, its tensile strength is significantly improved. This makes N08810 corrosion-resistant alloy very widely used in high-temperature environments, such as aerospace, chemical, energy and other industries. However, N08810 corrosion-resistant alloy contains a high content of Mo, W, Cr, Fe elements, and a certain amount of C element. During the solidification process of the ingot, there is element segregation and a large amount of carbides (M6C, M2C, M23C6) precipitation, resulting in a large deformation resistance of N08810 corrosion-resistant alloy, and forging cracking often occurs, causing huge economic losses. In addition, the thermal conductivity of N08810 corrosion-resistant alloy is low and the linear expansion coefficient is large. During the heating process of forging, the temperature gradient between the surface and the core of the ingot is large, and the thermal stress is large, which causes heating cracking. Moreover, the alloy has severe heat dissipation in the process of being made into steel plates, which makes it easy to deform and crack, and the plate forming rate is low. Summary of the invention

[0003] The purpose of the present invention is to solve the above technical problems and to provide a method for forging N08810 steel plates which is not easy to deform and crack after the plates are formed and has a high plate forming rate.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for forging a N08810 steel plate, characterized in that it comprises the following steps:

[0006] Step 1: In the first stage of heating, the N08810 steel ingot is heated to 580°C to 620°C and kept warm for 4 to 6 hours; in the second stage of heating, the temperature is raised to 910 to 940°C at a heating rate of 1 to 3°C / min and kept warm for 2 to 3 hours;

[0007] Step 2, heating the N08810 steel ingot obtained in step 1 to 1165° C. to 1195° C. at a heating rate of 2 to 4° C. / min, and then keeping the temperature for 8 to 12 hours;

[0008] Step 3, cooling the N08810 steel ingot obtained in step 3 to 1135° C. to 1155° C. at a cooling rate of 1 to 2° C. / min, and then keeping the temperature for 2 to 4 hours;

[0009] Step 4: Encapsulation before the first forging: Encapsulation is performed on the blank obtained in step 3. The encapsulation material is stainless steel or titanium alloy. A heat-resistant glass anti-oxidation coating is applied between the encapsulation material and the N08810 steel ingot.

[0010] Step 5: First fire forging: forging the steel ingot in step 4, pressing it down by 30% to 48% in the thickness direction, cutting the cap after forging, and returning it to the furnace for insulation for 3 to 5 hours;

[0011] Step 6: Removing the first rolling sheath: Using a mechanical processing method to remove the sheath of the steel plate with sheath obtained in step 5, obtaining the N08810 steel plate

[0012] Step 7: Sheathing before the second forging: the blank obtained in step 6 is sheathed, the sheath material is stainless steel or titanium alloy, and a heat-resistant glass anti-oxidation coating is applied between the sheath material and the N08810 steel ingot;

[0013] Step 8: Second forging: forging the steel ingot in step 7, pressing it down by 22% to 24% in the thickness direction, and returning it to the furnace for insulation for 3 to 5 hours after forging;

[0014] Step nine, removing the second rolling sheath: removing the sheath of the steel plate with sheath obtained in step eight by mechanical processing to obtain N08810 steel plate;

[0015] Step 10: Sheathing before the third forging: the blank obtained in step 9 is sheathed, the sheath material is stainless steel or titanium alloy, and a heat-resistant glass anti-oxidation coating is applied between the sheath material and the N08810 steel ingot;

[0016] Step 11, third fire forging, forging the steel ingot in step 10, pressing down 14% to 16% in the thickness direction;

[0017] Step 12, removing the third rolling sheath: using a mechanical processing method to remove the sheath of the steel plate with sheath obtained in step 11 to obtain a N08810 steel plate.

[0018] A further preferred technical solution is that the heating in step one and step two is carried out by using a trolley furnace, and the furnace temperature uniformity is ensured to be ±15°C.

[0019] There are many benefits to using a trolley furnace to heat steel ingots. It is suitable for large workpieces: the trolley furnace is particularly suitable for pre-forging heating of large steel ingots, billets, etc. that are inconvenient to heat in a chamber furnace, as well as heat treatment heating of large castings, forgings, and welded parts. Convenience of operation: The bottom of the trolley furnace is a movable trolley, which can be loaded outside the furnace, and then the trolley is moved into the furnace for heating. After the heating is completed, it can be pulled out of the furnace to unload. This design makes the operation more convenient, especially for large and complex workpieces. Accurate temperature control: The furnace temperature of the trolley furnace can complete a complete heating cycle in the furnace according to the process requirements, and the heating process can be adjusted arbitrarily within a large range, which helps to ensure the uniformity and accuracy of the heating process. Strong adaptability: The trolley furnace can adapt to workpieces of different geometries, sizes and weights, which makes it highly flexible and adaptable. High thermal efficiency: The design of the trolley furnace is conducive to reducing heat radiation and convection losses, effectively ensuring the sealing of the furnace body, thereby improving thermal efficiency. High safety: The movable mechanism of the electric furnace adopts interlocking control. For example, the power supply of the heating element is automatically cut off when the furnace door is opened, and the power supply is restored after the furnace door is closed. This can prevent accidents caused by misoperation.

[0020] A further preferred technical solution is that when the cap opening is cut off in step five, a portion of the slab having the same width as the steel plate is cut off together.

[0021] A further preferred technical solution is that the amount of the cap mouth removed in step 5 is ≥10%, and the tail of the N08810 steel plate is not removed after forging.

[0022] A further preferred technical solution is that in step 4, the ratio of the thickness of the N08810 steel plate before the first hot rolling to the thickness of the sheathing material is 3 to 6.

[0023] A further preferred technical solution is that the ratio of the thickness of the N08810 steel plate before the second and third fire rolling to the thickness of the sheathing material is 0.5-3.

[0024] A further preferred technical solution is that the steel ingot is subjected to ultrasonic vibration treatment during the forging process in the steps 5, 8 and 11. Ultrasonic vibration of the steel ingot after the jacket during the forging process can reduce the friction and extrusion force during the extrusion process, make the steel ingot easier to flow, reduce the internal stress caused by the temperature difference during the deformation process, and inhibit the generation of thermal cracks; in particular, it can significantly improve the fluidity of the steel ingot during the hot extrusion deformation process, and realize the extrusion forming of high-strength and low-elongation steel ingots.

[0025] In order to ensure the effect while avoiding excessive vibration of the steel ingot during the extrusion process due to excessive frequency, thereby failing to ensure the dimensional accuracy of the product, a further preferred technical solution is that the frequency of the ultrasonic vibration is 2kHz-50kHz.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention reduces the temperature difference between the surface and the core of the steel ingot by slowly heating up in stages, reduces thermal stress, and can avoid the risk of cracking of the N08810 steel ingot caused by thermal stress. Diffusion annealing is used to homogenize the element segregation, and the carbides in the grain boundaries can be dissolved back into the grains, so that the carbides inside the N08810 corrosion-resistant alloy steel ingot and the element segregation are basically eliminated. In addition, the cooling process in the forging method increases the high-temperature strength of the N08810 corrosion-resistant alloy steel ingot, preventing surface cracking during forging and blanking. In addition, the present invention can effectively inhibit the occurrence of hydrogen absorption, oxygen absorption and severe heat dissipation through jacket forging, ensuring that the mechanical properties of the plate are at a high level. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the metallographic diagram of Example 1 after forging in the present invention. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0029] Embodiment 1

[0030] A method for forging a N08810 steel plate is forging a steel ingot with a thickness of 800 mm, a width of 1600 mm, a length of 2500 mm, and a cap opening of 550 mm. The specific steps are as follows:

[0031] Step 1: In the first stage of heating, the N08810 steel ingot is heated to 600°C and kept at this temperature for 5 hours; in the second stage of heating, the temperature is raised to 930°C at a heating rate of 2°C / min and kept at this temperature for 3 hours;

[0032] Step 2: Heat the N08810 steel ingot that has completed step 1 to 1180°C at a heating rate of 4°C / min, and keep it warm for 12 hours; the heating in steps 1 and 2 is both heated by a trolley furnace, and the furnace temperature uniformity is guaranteed to be ±15°C.

[0033] Step 3, cooling the N08810 steel ingot obtained in step 3 to 1155°C at a cooling rate of 2°C / min, and then keeping the temperature for 4 hours;

[0034] Step 4: Encasement before the first forging: Encase the blank obtained in step 3. The encasement material is 304 stainless steel. A heat-resistant glass anti-oxidation coating is applied between the encasement material and the N08810 steel ingot. The ratio of the blank thickness to the encasement material thickness is 5.

[0035] Step 5, the first fire forging, forging the steel ingot in step 4, pressing it down to 490mm in thickness direction, and using ultrasonic vibration at a frequency of 25kHz during the forging process, cutting the cap mouth after forging, returning to the furnace for 4h of heat preservation, and when the cap mouth is cut, part of the slab with the same width as the steel plate is cut together, and the amount of cap mouth cut is 10%;

[0036] Step 6: Removing the first rolling sheath: Using a mechanical processing method to remove the sheath of the steel plate with sheath obtained in step 5, obtaining a steel plate blank of 2500mm*1600mm*490mm

[0037] Step 7: Sheathing before the second forging: the blank obtained in step 6 is sheathed, the sheath material is 304 stainless steel, a heat-resistant glass anti-oxidation coating is applied between the sheath material and the N08810 steel ingot, and the ratio of the thickness of the rolled plate to the thickness of the sheath material is 2;

[0038] Step 8: Second forging: forge the steel ingot in step 7, press it down to 380mm in thickness direction, and use ultrasonic vibration at a frequency of 2kHz during forging. After forging, return to the furnace and keep warm for 4h;

[0039] Step nine, removing the second rolling jacket: using a mechanical processing method to remove the jacket of the steel plate with the jacket obtained in step eight, to obtain a steel plate of 2500mm*1600mm*380mm;

[0040] Step 10: jacketing before the third forging. The blank obtained in step 9 is jacketed. The jacket material is stainless steel or titanium alloy. A heat-resistant glass anti-oxidation coating is applied between the jacket material and the N08810 steel ingot. The ratio of the thickness of the rolled plate to the thickness of the jacket material is 1.5.

[0041] Step 11, third fire forging, forging the steel ingot in step 10, and using ultrasonic vibration at a frequency of 50 kHz during the forging process, and pressing down to 320 mm in the thickness direction;

[0042] Step 12, removing the third rolling sheath: using a mechanical processing method to remove the sheath of the steel plate with sheath obtained in step 11, to obtain a 2500mm*1600mm*320mm N08810 steel plate.

[0043] The plate passed the ultrasonic flaw detection test. According to the metallographic analysis, the dendrites inside the forging disappeared, there was no carbide, and the element segregation was basically eliminated. Figure 1As shown, the plate has a great improvement in mechanics compared to the plates produced in the past. The present invention reduces the temperature difference between the surface and the core of the steel ingot by slowly heating up in stages, reduces thermal stress, and avoids the risk of cracking of the N08810 steel ingot caused by thermal stress. Diffusion annealing is used to homogenize the element segregation, and the carbides in the grain boundaries can be dissolved back into the grains, so that the carbides inside the N08810 corrosion-resistant alloy steel ingot basically eliminate the element segregation. In addition, the cooling process in the forging method increases the high-temperature strength of the N08810 corrosion-resistant alloy steel ingot, preventing surface cracking during forging and blanking. In addition, the present invention can effectively suppress the occurrence of hydrogen absorption, oxygen absorption and severe heat dissipation through jacket forging, ensuring that the mechanical properties of the plate are at a high level.

[0044] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for forging a N08810 steel plate, characterized in that: The following steps are involved: Step 1: In the first stage of heating, the N08810 steel ingot is heated to 580°C to 620°C and kept warm for 4 to 6 hours; in the second stage of heating, the temperature is raised to 910 to 940°C at a heating rate of 1 to 3°C / min and kept warm for 2 to 3 hours; Step 2, heating the N08810 steel ingot obtained in step 1 to 1165° C. to 1195° C. at a heating rate of 2 to 4° C. / min, and then keeping the temperature for 8 to 12 hours; Step 3, cooling the N08810 steel ingot obtained in step 3 to 1135° C. to 1155° C. at a cooling rate of 1 to 2° C. / min, and then keeping the temperature for 2 to 4 hours; Step 4: Encapsulation before the first forging: Encapsulation is performed on the blank obtained in step 3. The encapsulation material is stainless steel or titanium alloy. A heat-resistant glass anti-oxidation coating is applied between the encapsulation material and the N08810 steel ingot. Step 5: First fire forging: forging the steel ingot in step 4, pressing it down by 30% to 48% in the thickness direction, cutting the cap after forging, and returning it to the furnace for insulation for 3 to 5 hours; Step 6, removing the first rolling sheath: removing the sheath of the steel plate with sheath obtained in step 5 by mechanical processing to obtain N08810 steel plate; Step 7: Sheathing before the second forging: the steel plate obtained in step 6 is sheathed, the sheath material is stainless steel or titanium alloy, and a heat-resistant glass anti-oxidation coating is applied between the sheath material and the N08810 steel ingot; Step 8: Second forging: forging the steel ingot in step 7, pressing it down by 22% to 24% in the thickness direction, and returning it to the furnace for insulation for 3 to 5 hours after forging; Step nine, removing the second rolling sheath: removing the sheath of the steel plate with sheath obtained in step eight by mechanical processing to obtain N08810 steel plate; Step 10: jacketing before the third forging: the steel plate obtained in step 9 is jacketed, the jacket material is stainless steel or titanium alloy, and a heat-resistant glass anti-oxidation coating is applied between the jacket material and the N08810 steel ingot; Step 11, third fire forging, forging the steel ingot in step 10, pressing down 14% to 16% in the thickness direction; Step 12, removing the third rolling sheath: using a mechanical processing method to remove the sheath of the steel plate with sheath obtained in step 11 to obtain a N08810 steel plate.

2. A N08810 steel plate forging method as claimed in claim 1, characterized in that: The heating in step 1 and step 2 is carried out by a trolley furnace, and the furnace temperature uniformity is ensured to be ±15°C.

3. A N08810 steel plate forging method as claimed in claim 1, characterized in that: When the cap opening is cut in step 5, a portion of the slab having the same width as the steel plate is cut together.

4. A N08810 steel plate forging method as claimed in claim 1, characterized in that: In the step 5, the amount of the cap cut is ≥10%, and the tail of the N08810 steel plate is not cut after forging.

5. A N08810 steel plate forging method as claimed in claim 1, characterized in that: In the step 4, the ratio of the thickness of the N08810 steel plate before the first hot rolling to the thickness of the sheathing material is 3 to 6.

6. A N08810 steel plate forging method as claimed in claim 1, characterized in that: The ratio of the thickness of the N08810 steel plate to the thickness of the sheathing material before the second and third rolling is 0.5-3.

7. A N08810 steel plate forging method as claimed in claim 1, characterized in that: During the forging process in step five, step eight and step eleven, the steel ingot is subjected to ultrasonic vibration treatment.

8. A N08810 steel plate forging method as claimed in claim 7, characterized in that: The frequency of the ultrasonic vibration is 2kHz-50kHz.

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