Creep resistant stainless steel material for welded pipe

Abstract

The present application relates to the technical field of stainless steel material, and proposes a creep-resistant stainless steel material for welded pipe, which is composed of the following components by weight percentage: C 0.08%~0.1%, Si 0.8%~1.0%, Mn 1.6%~1.8%, Ni 13.2%~15%, Cr 22%~24%, Mo 1.24%~3.18%, P≤0.04%, S≤0.03%, and the balance of Fe and inevitable impurities, wherein (Cr+Mo):(C+Ni)=1.75~1.80:1. Through the above technical solution, the problem of poor creep resistance of the stainless steel material for welded pipe in the related art is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of stainless steel materials, in particular to a creep-resistant stainless steel material for welded pipes. BACKGROUND

[0002] Welded pipes are often used in harsh environments with high temperature, high pressure and certain stress. Ordinary stainless steel is prone to creep under the action of high temperature and long-term load. Creep refers to the slow plastic deformation of materials under certain stress at high temperature. With the passage of time, this deformation will gradually accumulate, eventually leading to material failure, affecting the safety and stability of the equipment.

[0003] If the stainless steel material for welded pipes does not have creep resistance, the welded pipe will gradually creep under the action of long-term high temperature, high pressure and stress, resulting in an increase in pipe diameter and a decrease in pipe wall thickness. This not only reduces the carrying capacity of the welded pipe and causes safety accidents such as pipe leakage, but also threatens production safety and may reduce the operating efficiency of the entire system, resulting in significant economic losses. Therefore, it is crucial for stainless steel materials for welded pipes to have good creep resistance.

[0004] Therefore, it is necessary to develop a stainless steel material for welded pipes with creep resistance. SUMMARY

[0005] The present application provides a creep-resistant stainless steel material for welded pipes, which solves the problem of poor creep resistance of stainless steel materials for welded pipes in related technologies.

[0006] The technical solution of the present application is as follows: the present application provides a creep-resistant stainless steel material for welded pipes, which is composed of the following components by weight percentage: C 0.08%~0.1%, Si 0.8%~1.0%, Mn 1.6%~1.8%, Ni 13.2%~15%, Cr 22%~24%, Mo 1.24%~3.18%, P≤0.04%, S≤0.03%, the balance being Fe and unavoidable impurities, wherein (Cr+Mo):(C+Ni)=1.75~1.80:1.

[0007] Carbon (C, 0.08%~0.1%): Carbon is an important strengthening element in steel, which can form carbides with chromium and molybdenum, and can enhance the creep resistance of the material.

[0008] Silicon (Si, 0.8%~1.0%): As a strong deoxidizing agent, it can remove excess oxygen in steel, reduce oxide inclusions, improve the purity of steel, and improve the quality of smelting.

[0009] Manganese (Mn, 1.6%~1.8%): Manganese can reduce the high-temperature deformation resistance of stainless steel, improve the plasticity of the material during hot working, and make the blank more easily rolled into plate, pipe or profile. Especially for welded pipe, good thermal plasticity can reduce the risk of cracking during welding.

[0010] Nickel (Ni, 13.2%~15%): Nickel is the core element of austenitic stainless steel, which can stabilize the austenitic structure at room temperature and high temperature, ensuring that the material still has good plasticity and toughness at high temperature.

[0011] Chromium (Cr, 22%~24%): Chromium is a key element for corrosion resistance of stainless steel, which can not only prevent the substrate from being oxidized or corroded, but also form carbides uniformly distributed in the matrix, further hindering dislocation slip, significantly improving the use reliability of stainless steel material.

[0012] Molybdenum (Mo, 1.24%~3.18%): Molybdenum can slow down the precipitation and coarsening speed of carbides at high temperature, maintain the strength of grain boundary, and reduce creep deformation.

[0013] As a further technical solution, the preparation method of the creep-resistant stainless steel material for welded pipe includes the following steps: proportioning according to the weight percentage of the components, smelting, continuous casting, hot rolling, hot rolling annealing and pickling, cold rolling, cold rolling annealing and pickling, and flattening to obtain the creep-resistant stainless steel material for welded pipe.

[0014] As a further technical solution, the hot rolling includes the following steps: heating the continuous casting blank to 1150~1200℃, for example, it can be 1150℃, 1160℃, 1170℃, 1180℃, 1190℃, 1200℃, preferably 1200℃; holding for 200~240min for hot rolling, for example, it can be 200min, 210min, 220min, 230min, 240min, preferably 220min, and the final rolling temperature is 950~1000℃, for example, it can be 950℃, 960℃, 970℃, 980℃, 990℃, 1000℃, preferably 980℃.

[0015] As a further technical solution, the hot rolling is cooled to 400~450℃, for example, it can be 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, preferably 400℃, the cooling method is water cooling, and the cooling includes first-stage cooling and second-stage cooling, the cooling rates of the first-stage cooling and the second-stage cooling are different.

[0016] As a further technical solution, the cooling comprises the following steps: after the hot rolling, first cooling is carried out, and the cooling is to 650-700 DEG C, for example, it can be 650 DEG C, 660 DEG C, 670 DEG C, 680 DEG C, 690 DEG C, 700 DEG C, preferably 680 DEG C, then second cooling is carried out, and the cooling is to 400-450 DEG C, for example, it can be 400 DEG C, 410 DEG C, 420 DEG C, 430 DEG C, 440 DEG C, 450 DEG C, preferably 440 DEG C.

[0017] As a further technical solution, the cooling rate of the first cooling is greater than the cooling rate of the second cooling, the cooling rate of the first cooling is 70-80 DEG C / s, for example, it can be 70 DEG C / s, 71 DEG C / s, 72 DEG C / s, 73 DEG C / s, 74 DEG C / s, 75 DEG C / s, 76 DEG C / s, 77 DEG C / s, 78 DEG C / s, 79 DEG C / s, 80 DEG C / s, preferably 70 DEG C / s, and the cooling rate of the second cooling is 20-30 DEG C / s, for example, it can be 20 DEG C / s, 21 DEG C / s, 22 DEG C / s, 23 DEG C / s, 24 DEG C / s, 25 DEG C / s, 26 DEG C / s, 27 DEG C / s, 28 DEG C / s, 29 DEG C / s, 30 DEG C / s, preferably 20 DEG C / s.

[0018] In the preparation process of the creep-resistant stainless steel material for welded pipe, the hot rolling cooling is in the form of segmented cooling, wherein the cooling speed of the first cooling is high, which can avoid the grain coarsening caused by the long residence time of the material in the high temperature zone, and create suitable temperature conditions for the subsequent precipitation of the strengthening phase, and the cooling rate of the second cooling is low, which can further promote the uniform precipitation of alloy elements at the grain boundary, form a stable carbide strengthening phase, and effectively hinder the dislocation movement. The segmented cooling mode in the application not only ensures the grain refinement, but also realizes the uniform distribution of the strengthening phase, and under the synergistic action of the two, the tensile strength of the material is greatly improved.

[0019] As a further technical solution, the annealing temperature of the hot rolling annealing and pickling is 1080-1100 DEG C, for example, it can be 1080 DEG C, 1085 DEG C, 1090 DEG C, 1095 DEG C, 1100 DEG C, preferably 1100 DEG C.

[0020] In the preparation process of the anti-creep stainless steel material for welded pipe, the final rolling temperature of hot rolling and the annealing temperature of hot rolling annealing and pickling are at a high level, which is related to the element content in the stainless steel material. When the final rolling temperature is 950-1000 DEG C, the material maintains austenitic structure and good plasticity, and the grain refinement can be realized by rolling, which lays the organizational foundation for the subsequent tensile strength improvement; the annealing temperature is higher than the final rolling temperature, which can fully eliminate the thermal deformation stress, promote the uniform diffusion of alloying elements, inhibit the precipitation of coarse carbides, and the two process temperatures cooperate with each other, and the high temperature organizational stability given by the alloying elements is used to realize the synergy of grain refinement, composition homogenization and stress relief through reasonable temperature matching, and finally the tensile strength of the material is effectively improved.

[0021] As a further technical solution, in the process of hot rolling annealing and pickling, the pickling solution is nitric acid solution, the concentration of the nitric acid solution is 20-30 g / L, for example, it can be 21 g / L, 22 g / L, 23 g / L, 24 g / L, 25 g / L, 26 g / L, 27 g / L, 28 g / L, 29 g / L, 30 g / L, preferably 30 g / L.

[0022] As a further technical solution, the reduction of cold rolling is 60%-70%, for example, it can be 60%, 62%, 65%, 68%, 70%, preferably 65%.

[0023] As a further technical solution, the annealing process of cold rolling annealing and pickling includes: after cold rolling, heating to 950-1020 DEG C, holding for 30-40 min, then water cooling to 600-650 DEG C, and then air cooling to room temperature.

[0024] After cold rolling, heating to 950-1020 DEG C, for example, it can be 950 DEG C, 960 DEG C, 970 DEG C, 980 DEG C, 990 DEG C, 1000 DEG C, 1010 DEG C, 1020 DEG C, preferably 1000 DEG C;

[0025] Holding for 30-40 min, for example, it can be 30 min, 32 min, 35 min, 38 min, 40 min, preferably 35 min;

[0026] Water cooling to 600-650 DEG C, for example, it can be 600 DEG C, 610 DEG C, 620 DEG C, 630 DEG C, 640 DEG C, 650 DEG C, preferably 620 DEG C.

[0027] As a further technical solution, the cooling rate of the water cooling is greater than that of the air cooling. The cooling rate of the water cooling is 50~60℃ / s, for example, it can be 50℃ / s, 51℃ / s, 52℃ / s, 53℃ / s, 54℃ / s, 55℃ / s, 56℃ / s, 57℃ / s, 58℃ / s, 59℃ / s, or 60℃ / s, preferably 50℃ / s; the cooling rate of the air cooling is 5~10℃ / s, for example, it can be 5℃ / s, 6℃ / s, 7℃ / s, 8℃ / s, 9℃ / s, or 10℃ / s, preferably 10℃ / s.

[0028] In the preparation process of the creep-resistant stainless steel material for welded pipes of this invention, during the cold rolling, annealing, and pickling steps, the annealing cooling adopts a cooling method of first water cooling and then air cooling, and the cooling rates of the two cooling methods are different. The faster water cooling rate cools the temperature to 600~650℃, which can quickly suppress the growth trend of austenite grains, avoid the excessive precipitation of alloying elements at the grain boundaries to form coarse carbides, and reduce grain boundary weakening caused by the aggregation of second phase particles. Then, the slower air cooling is switched to release some internal stress through slow cooling. The combination of the two cooling methods makes the grain structure of the stainless steel material more compact and effectively optimizes the tensile strength of the stainless steel material.

[0029] As a further technical solution, in the process of cold rolling annealing pickling, the pickling solution used is a nitric acid solution with a concentration of 20~30g / L, for example, 20g / L, 22g / L, 25g / L, 28g / L, or 30g / L, preferably 25g / L.

[0030] The working principle and beneficial effects of this invention are as follows:

[0031] In the elemental composition of the anti-creep stainless steel material for welded pipes of this invention, the elemental composition satisfies (Cr+Mo):(C+Ni)=1.75~1.80:1. The content of Ni element can stabilize the austenite matrix, laying the foundation for the microstructure stability at high temperatures. The austenite structure itself has better dislocation migration resistance, which can effectively suppress plastic deformation at high temperatures. Cr and Mo elements can form carbides, which can pin grain boundaries and dislocations, hindering dislocation movement, and are the core strengthening phase for anti-creep. C element is the key to carbide formation. When the elemental composition satisfies (Cr+Mo):(C+Ni)=1.75~1.80:1, it ensures a sufficient amount of carbide precipitation to strengthen the intragranular and grain boundary regions, while avoiding carbide coarsening due to excessive C element. This helps to form a uniformly distributed, small-sized, and thermally stable strengthening phase, thereby effectively suppressing creep mechanisms such as dislocation slip, grain boundary slip, and coarsening of precipitated phases at high temperatures, and improving the creep resistance of the anti-creep stainless steel material for welded pipes. Detailed Implementation

[0032] With reference to the drawings and the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by those skilled in the art without creative work, are within the scope of protection of the present application.

[0033] Embodiment 1

[0034] A creep-resistant stainless steel material for welded pipe is composed of the following components in percentage by weight: C 0.08%, Si 0.8%, Mn 1.6%, Ni 13.2%, Cr 22%, Mo 1.24%, P 0.04%, S 0.03%, and the balance of Fe and inevitable impurities;

[0035] A method for preparing the creep-resistant stainless steel material for welded pipe comprises the following steps: proportioning the components by weight, smelting and continuous casting to obtain a continuous casting billet, heating the continuous casting billet to 1150℃, heat rolling for 220min, the final rolling temperature being 950℃, after heat rolling, using water cooling as the cooling method, cooling to 400℃ at a cooling rate of 70℃ / s, setting the annealing temperature to 1080℃ for heat rolling annealing and pickling, using nitric acid solution (concentration of 20g / L) for pickling, setting the cold rolling reduction to 60% for cold rolling, setting the annealing temperature to 950℃ for cold rolling annealing and pickling, the holding time being 40min, the cooling method being water cooling, the cooling rate being 50℃ / s, cooling to room temperature, using nitric acid solution (concentration of 20g / L) for pickling, and obtaining the creep-resistant stainless steel material for welded pipe after flattening.

[0036] Embodiment 2

[0037] A creep-resistant stainless steel material for welded pipe is composed of the following components in percentage by weight: C 0.09%, Si 0.9%, Mn 1.7%, Ni 14.01%, Cr 23%, Mo 2.0%, P 0.04%, S 0.03%, and the balance of Fe and inevitable impurities;

[0038] The preparation method of the creep-resistant stainless steel material for welded pipe comprises the following steps: proportioning components by weight percentage, obtaining a continuous casting billet through smelting and continuous casting, heating the continuous casting billet to 1200℃, heat rolling for 220min, the final rolling temperature is 980℃, after heat rolling, using water cooling as the cooling method, cooling to 400℃ at a cooling rate of 70℃ / s, setting the annealing temperature to 1100℃ for heat rolling annealing and pickling, using nitric acid solution (concentration of 30g / L) for pickling, setting the cold rolling reduction to 65% for cold rolling, setting the annealing temperature to 1000℃ for cold rolling annealing and pickling, the holding time is 35min, the cooling method is water cooling, the cooling rate is 50℃ / s, cooling to room temperature, using nitric acid solution (concentration of 25g / L) for pickling, and obtaining the creep-resistant stainless steel material for welded pipe after flattening.

[0039] Example 3

[0040] A creep-resistant stainless steel material for welded pipe is composed of the following components by weight percentage: C 0.1%, Si 1.0%, Mn 1.8%, Ni 15%, Cr 24%, Mo 3.18%, P 0.04%, S 0.03%, and the balance of Fe and inevitable impurities.

[0041] The preparation method of the creep-resistant stainless steel material for welded pipe comprises the following steps: proportioning components by weight percentage, obtaining a continuous casting billet through smelting and continuous casting, heating the continuous casting billet to 1200℃, heat rolling for 240min, the final rolling temperature is 1000℃, after heat rolling, using water cooling as the cooling method, cooling to 450℃ at a cooling rate of 70℃ / s, setting the annealing temperature to 1100℃ for heat rolling annealing and pickling, using nitric acid solution (concentration of 30g / L) for pickling, setting the cold rolling reduction to 70% for cold rolling, setting the annealing temperature to 1100℃ for cold rolling annealing and pickling, the holding time is 30min, the cooling method is water cooling, the cooling rate is 50℃ / s, cooling to room temperature, using nitric acid solution (concentration of 30g / L) for pickling, and obtaining the creep-resistant stainless steel material for welded pipe after flattening.

[0042] Example 4

[0043] Compared with Example 2, the difference of Example 4 is that the creep-resistant stainless steel material for welded pipe is composed of the following components by weight percentage: C 0.09%, Si 0.9%, Mn 1.7%, Ni 14.01%, Cr 23%, Mo 1.82%, P 0.04%, S 0.03%, and the balance of Fe and inevitable impurities.

[0044] Example 5

[0045] Example 5 differs from Example 2 in that the creep-resistant stainless steel material for welded pipes is composed of the following components in weight percentage: C 0.09%, Si 0.9%, Mn 1.7%, Ni 14.01%, Cr 23%, Mo 2.24%, P 0.04%, S 0.03%, with the balance being Fe and unavoidable impurities.

[0046] Example 6

[0047] Example 6 differs from Example 2 in that the method for preparing the creep-resistant stainless steel material for welded pipes is different. In this example, the method for preparing the creep-resistant stainless steel material for welded pipes includes the following steps: batching components in weight percentage, smelting and continuous casting to obtain a continuous casting billet, heating the continuous casting billet to 1200°C, hot rolling for 220 min with a final rolling temperature of 980°C, using water cooling as the cooling method after hot rolling, cooling to 400°C at a cooling rate of 20°C / s, setting the annealing temperature to 1100°C for hot rolling annealing and pickling, using a nitric acid solution (concentration of 30 g / L) for pickling, setting the cold rolling reduction to 65% for cold rolling, setting the annealing temperature to 1000°C for cold rolling annealing and pickling, setting the holding time to 35 min, using water cooling as the cooling method, setting the cooling rate to 50°C / s, cooling to room temperature, using a nitric acid solution (concentration of 25 g / L) for pickling, and flattening to obtain the creep-resistant stainless steel material for welded pipes.

[0048] Example 7

[0049] Example 7 differs from Example 2 in that the method for preparing the creep-resistant stainless steel material for welded pipes is different. In this example, the method for preparing the creep-resistant stainless steel material for welded pipes includes the following steps: batching components in weight percentage, smelting and continuous casting to obtain a continuous casting billet, heating the continuous casting billet to 1200°C, hot rolling for 220 min with a final rolling temperature of 980°C, using water cooling as the cooling method after hot rolling, first cooling to 680°C at a cooling rate of 70°C / s, then cooling to 400°C at a cooling rate of 20°C / s, setting the annealing temperature to 1100°C for hot rolling annealing and pickling, using a nitric acid solution (concentration of 30 g / L) for pickling, setting the cold rolling reduction to 65% for cold rolling, setting the annealing temperature to 1000°C for cold rolling annealing and pickling, setting the holding time to 35 min, using water cooling as the cooling method, setting the cooling rate to 50°C / s, cooling to room temperature, using a nitric acid solution (concentration of 25 g / L) for pickling, and flattening to obtain the creep-resistant stainless steel material for welded pipes.

[0050] Example 8

[0051] Compared with Example 2, the difference of Example 8 lies in the different preparation method of the creep-resistant stainless steel material for welded pipes. The preparation method of the creep-resistant stainless steel material for welded pipes in the present example comprises the following steps: proportioning components by weight percentage, obtaining a continuous casting billet through smelting and continuous casting, heating the continuous casting billet to 1200℃, heat rolling for 220min, the final rolling temperature is 980℃, after heat rolling, using water cooling as the cooling method, first cooling to 680℃ at a cooling rate of 20℃ / s, then cooling to 400℃ at a cooling rate of 70℃ / s, setting the annealing temperature to 1100℃ for heat rolling annealing and pickling, using nitric acid solution (concentration of 30g / L) for pickling, setting the cold rolling reduction to 65% for cold rolling, setting the annealing temperature to 1000℃ for cold rolling annealing and pickling, the holding time is 35min, the cooling method is water cooling, the cooling rate is 50℃ / s, cooling to room temperature, using nitric acid solution (concentration of 25g / L) for pickling, and obtaining the creep-resistant stainless steel material for welded pipes after flattening.

[0052] Example 9

[0053] Compared with Example 2, the difference of Example 9 lies in the different preparation method of the creep-resistant stainless steel material for welded pipes. The preparation method of the creep-resistant stainless steel material for welded pipes in the present example comprises the following steps: proportioning components by weight percentage, obtaining a continuous casting billet through smelting and continuous casting, heating the continuous casting billet to 1200℃, heat rolling for 220min, the final rolling temperature is 980℃, after heat rolling, using water cooling as the cooling method, first cooling to 680℃ at a cooling rate of 50℃ / s, then cooling to 400℃ at a cooling rate of 20℃ / s, setting the annealing temperature to 1100℃ for heat rolling annealing and pickling, using nitric acid solution (concentration of 30g / L) for pickling, setting the cold rolling reduction to 65% for cold rolling, setting the annealing temperature to 1000℃ for cold rolling annealing and pickling, the holding time is 35min, the cooling method is water cooling, the cooling rate is 50℃ / s, cooling to room temperature, using nitric acid solution (concentration of 25g / L) for pickling, and obtaining the creep-resistant stainless steel material for welded pipes after flattening.

[0054] Example 10

[0055] Compared with Example 7, the difference of Example 10 lies in the different preparation method of the creep-resistant stainless steel material for welded pipes. The preparation method of the creep-resistant stainless steel material for welded pipes in the present example comprises the following steps: proportioning components by weight percentage, obtaining a continuous casting billet through smelting and continuous casting, heating the continuous casting billet to 1200℃, heat rolling for 220 min, the final rolling temperature is 850℃, after heat rolling, using water cooling as the cooling method, first cooling to 680℃ at a cooling rate of 70℃ / s, then cooling to 400℃ at a cooling rate of 20℃ / s, setting the annealing temperature to 1100℃ for heat rolling annealing and pickling, using nitric acid solution (concentration of 30g / L) for pickling, setting the cold rolling reduction to 65% for cold rolling, setting the annealing temperature to 1000℃ for cold rolling annealing and pickling, the holding time is 35 min, the cooling method is water cooling, the cooling rate is 50℃ / s, cooling to room temperature, using nitric acid solution (concentration of 25g / L) for pickling, and obtaining the creep-resistant stainless steel material for welded pipes after flattening.

[0056] Example 11

[0057] Compared with Example 7, the difference of Example 11 lies in the different preparation method of the creep-resistant stainless steel material for welded pipes. The preparation method of the creep-resistant stainless steel material for welded pipes in the present example comprises the following steps: proportioning components by weight percentage, obtaining a continuous casting billet through smelting and continuous casting, heating the continuous casting billet to 1200℃, heat rolling for 220 min, the final rolling temperature is 980℃, after heat rolling, using water cooling as the cooling method, first cooling to 680℃ at a cooling rate of 70℃ / s, then cooling to 400℃ at a cooling rate of 20℃ / s, setting the annealing temperature to 1000℃ for heat rolling annealing and pickling, using nitric acid solution (concentration of 30g / L) for pickling, setting the cold rolling reduction to 65% for cold rolling, setting the annealing temperature to 1000℃ for cold rolling annealing and pickling, the holding time is 35 min, the cooling method is water cooling, the cooling rate is 50℃ / s, cooling to room temperature, using nitric acid solution (concentration of 25g / L) for pickling, and obtaining the creep-resistant stainless steel material for welded pipes after flattening.

[0058] Example 12

[0059] Compared with Example 7, the difference of Example 12 lies in the different preparation method of the creep-resistant stainless steel material for welded pipes. The preparation method of the creep-resistant stainless steel material for welded pipes in the present example comprises the following steps: proportioning components by weight percentage, obtaining a continuous casting billet through smelting and continuous casting, heating the continuous casting billet to 1200℃, hot rolling for 220min, the final rolling temperature is 980℃, after hot rolling, using water cooling as the cooling method, first cooling to 680℃ at a cooling rate of 70℃ / s, then cooling to 400℃ at a cooling rate of 20℃ / s, setting the annealing temperature to 1100℃ for hot rolling annealing and pickling, using nitric acid solution (concentration of 30g / L) for pickling, setting the cold rolling reduction to 65% for cold rolling, setting the annealing temperature to 1000℃ for cold rolling annealing and pickling, the holding time is 35min, the cooling method is air cooling, the cooling rate is 10℃ / s, cooling to room temperature, using nitric acid solution (concentration of 25g / L) for pickling, and obtaining the creep-resistant stainless steel material for welded pipes after flattening.

[0060] Example 13

[0061] Compared with Example 7, the difference of Example 13 lies in the different preparation method of the creep-resistant stainless steel material for welded pipes. The preparation method of the creep-resistant stainless steel material for welded pipes in the present example comprises the following steps: proportioning components by weight percentage, obtaining a continuous casting billet through smelting and continuous casting, heating the continuous casting billet to 1200℃, hot rolling for 220min, the final rolling temperature is 980℃, after hot rolling, using water cooling as the cooling method, first cooling to 680℃ at a cooling rate of 70℃ / s, then cooling to 400℃ at a cooling rate of 20℃ / s, setting the annealing temperature to 1100℃ for hot rolling annealing and pickling, using nitric acid solution (concentration of 30g / L) for pickling, setting the cold rolling reduction to 65% for cold rolling, setting the annealing temperature to 1000℃ for cold rolling annealing and pickling, the holding time is 35min, the cooling method is first water cooling at a cooling rate of 50℃ / s to 620℃, then air cooling at a cooling rate of 10℃ / s to room temperature, using nitric acid solution (concentration of 25g / L) for pickling, and obtaining the creep-resistant stainless steel material for welded pipes after flattening.

[0062] Example 14

[0063] The difference between Example 14 and Example 7 is that the preparation method of the creep-resistant stainless steel material for welded pipes is different. In this embodiment, the preparation method of the creep-resistant stainless steel material for welded pipes comprises the following steps: compounding components in percentage by weight, obtaining a continuous casting billet by smelting and continuous casting, heating the continuous casting billet to 1200℃, and hot rolling for 220min with a final rolling temperature of 980℃. After hot rolling, the cooling method is water cooling, first cooling to 680℃ at a cooling rate of 70℃ / s, and then cooling to 400℃ at a cooling rate of 20℃ / s. Hot rolling annealing pickling is performed at an annealing temperature of 1100℃, using a nitric acid solution (concentration of 30g / L) for pickling. Cold rolling is performed with a cold rolling reduction of 65%, and cold rolling annealing pickling is performed at an annealing temperature of 1000℃, with a holding time of 35min. The cooling method is first air cooling at a cooling rate of 10℃ / s to 620℃, and then water cooling at a cooling rate of 50℃ / s to room temperature. A nitric acid solution (concentration of 25g / L) is used for pickling. After flattening, the creep-resistant stainless steel material for welded pipes is obtained.

[0064] Comparative Example 1

[0065] Comparative Example 1 differs from Example 2 in that a creep-resistant stainless steel material for welded pipes is composed of the following components in percentage by weight: C 0.09%, Si 0.9%, Mn 1.7%, Ni 14.01%, Cr 23%, Mo 1%, P 0.04%, S 0.03%, and the balance being Fe and unavoidable impurities.

[0066] Comparative Example 2

[0067] Comparative Example 2 differs from Example 2 in that a creep-resistant stainless steel material for welded pipes is composed of the following components in percentage by weight: C 0.09%, Si 0.9%, Mn 1.7%, Ni 14.01%, Cr 23%, Mo 4%, P 0.04%, S 0.03%, and the balance being Fe and unavoidable impurities.

[0068] Experimental Example 1

[0069] The creep-resistant stainless steel materials for welded pipes obtained in Examples 1-5 and Comparative Examples 1-2 are tested. The test samples are tested for creep resistance. The test method is as follows: M12 rod-shaped samples are used, with a total length of 74mm and a gauge length of ψ6mm x 25mm. An air creep testing machine is used for testing. The test temperature is 650℃, and the loading stress is 180MPa. The temperature is raised to the test temperature at a rate of 10℃ / s. The measurement is started after 1 hour of holding, and the deformation amount at a creep time of 600h is recorded.

[0070] The test results are shown in Table 1:

[0071] Table 1 Performance test results of the creep-resistant stainless steel material for welded pipes prepared in Examples 1-5 and Comparative Examples 1-2

[0072]

[0073] As shown in Table 1, when the element composition of the creep-resistant stainless steel material for welded pipes meets the range requirements, and the element composition meets (Cr+Mo):(C+Ni)=1.75-1.80:1, the creep-resistant performance of the creep-resistant stainless steel material for welded pipes can be improved.

[0074] Experimental Example 2

[0075] The creep-resistant stainless steel material for welded pipes prepared in Example 2 and Examples 6-14 was tested, and the tensile strength of the test sample was tested. The test method was as follows: a tensile M6 rod-shaped sample meeting the requirements of the national standard was used, the total length was 47 mm, the gauge section was ψ3 mm x 15 mm, the tensile rate was 0.2 mm / min before the end of yield, and 1.8 mm / min after the end of yield, and the test conditions were: 650℃ aging for 1000h, and the test was carried out at 650℃.

[0076] The test results are shown in Table 2:

[0077] Table 2 Performance test results of the creep-resistant stainless steel material for welded pipes prepared in Example 2 and Examples 6-14

[0078]

[0079] As shown in Table 2, when the cooling method of hot rolling is water cooling, and the cooling is two-stage cooling, the tensile strength of the creep-resistant stainless steel material for welded pipes can be improved.

[0080] In the preparation process of the creep-resistant stainless steel material for welded pipes, when the finish rolling temperature of hot rolling is 980℃, and the annealing temperature of hot rolling annealing and pickling is 1100℃, the tensile strength of the creep-resistant stainless steel material for welded pipes can be further improved.

[0081] In the preparation process of the creep-resistant stainless steel material for welded pipes, when the cooling process of cold rolling annealing and pickling is cooled by using water cooling first and then air cooling, the tensile strength of the obtained creep-resistant stainless steel material for welded pipes is better.

[0082] The above is only a preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A creep resistant stainless steel material for welded pipe, characterized by, The welding pipe creep resistant stainless steel material is prepared by the following steps: ingredients are proportioned according to the weight percentage, smelting, continuous casting, hot rolling, hot rolling annealing and pickling, cold rolling, cold rolling annealing and pickling, and flattening to obtain the welding pipe creep resistant stainless steel material. The annealing process of the cold rolling annealing and pickling comprises the following steps: after cold rolling, heating to 950-1020 DEG C, holding for 30-40 min, then water cooling to 600-650 DEG C, and then air cooling to room temperature. The cooling rate of the water cooling is greater than the cooling rate of the air cooling, the cooling rate of the water cooling is 50-60 DEG C / s, and the cooling rate of the air cooling is 5-10 DEG C / s. The hot rolling comprises the following steps: heating the continuous casting blank to 1150-1200 DEG C, holding for 200-240 min for hot rolling, and final rolling temperature is 950-1000 DEG C.

2. A creep resistant stainless steel material for welded pipe according to claim 1, characterized in that, After hot rolling, cooling to 400-450 DEG C, the cooling mode is water cooling, and the cooling comprises first stage cooling and second stage cooling, and the cooling rates of the first stage cooling and the second stage cooling are different.

3. A creep resistant stainless steel material for welded pipe according to claim 2, characterized in that, The cooling comprises the following steps: after hot rolling, first stage cooling is performed to cool to 650-700 DEG C, and then second stage cooling is performed to cool to 400-450 DEG C.

4. A creep resistant stainless steel material for welded pipe according to claim 3, characterized in that, The cooling rate of the first stage cooling is greater than the cooling rate of the second stage cooling, the cooling rate of the first stage cooling is 70-80 DEG C / s, and the cooling rate of the second stage cooling is 20-30 DEG C / s.

5. A creep resistant stainless steel material for welded pipe according to claim 4, characterized in that, The annealing temperature of the hot rolling annealing and pickling is 1080-1100 DEG C.

6. A creep resistant stainless steel pipe material as claimed in claim 1, wherein, The cold rolling reduction is 60%-70%.

7. A creep resistant stainless steel pipe material as claimed in claim 1, wherein, ​

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