阅读说明：本技术 一种提高tp347hfg钢无缝钢管耐腐蚀性能的生产工艺方法 (Production process method for improving corrosion resistance of TP347HFG steel seamless steel pipe ) 是由 胡静 姚经松 周烨晖 于 2020-06-08 设计创作，主要内容包括：本发明属于金属材料改性技术领域,具体涉及一种提高TP347HFG钢无缝钢管耐腐蚀性能的生产工艺方法：将热轧穿孔后的荒管作为原始试样,然后高温一次固溶处理,获得铌元素充分溶解的粗晶组织,再进行冷轧大变形以充分细化粗晶,最后对无缝管进行长时间三段式二次固溶处理,从而使大变形晶粒充分均匀细化。该方法各步骤协同优化,在满足TP347HFG钢无缝钢管组织和力学性能的前提下,还达到改善组织、提高无缝钢管耐腐蚀性,特别是抗晶间腐蚀性的效果。TP347HFG钢无缝钢管应用于锅炉管,工作环境为高温,其抗晶间腐蚀性能的提高,能有效降低钢管内部组织晶间断裂的发生率,从而进一步提高其可靠性、稳定性和服役寿命。(The invention belongs to the technical field of metal material modification, and particularly relates to a production process method for improving the corrosion resistance of a TP347HFG steel seamless steel pipe, which comprises the following steps: the pierced billet after hot rolling and perforation is used as an original sample, then high-temperature primary solution treatment is carried out to obtain a coarse-grain structure with fully dissolved niobium element, then cold rolling large deformation is carried out to fully refine coarse grains, and finally long-time three-stage secondary solution treatment is carried out on the seamless tube, so that large-deformation grains are fully and uniformly refined. The method has the advantages that the steps are cooperatively optimized, and the effects of improving the structure and the corrosion resistance of the seamless steel tube, particularly the intergranular corrosion resistance are also achieved on the premise of meeting the structure and the mechanical property of the TP347HFG steel seamless steel tube. The TP347HFG steel seamless steel pipe is applied to a boiler pipe, the working environment is high temperature, the intergranular corrosion resistance of the pipe is improved, the intergranular fracture incidence rate of the internal structure of the steel pipe can be effectively reduced, and therefore the reliability, the stability and the service life of the pipe are further improved.)

1. A method for improving the corrosion resistance of a TP347HFG steel seamless steel pipe is characterized by comprising the following steps: the method comprises the following process steps:

(1) selecting a pierced billet obtained by hot piercing TP347HFG round steel as a sample;

(2) carrying out high-temperature primary solution treatment on the pierced billet;

(3) carrying out cold rolling and large deformation on the pierced billet subjected to the primary solution treatment after water cooling and acid pickling;

(4) carrying out three-stage secondary solution treatment on the steel pipe subjected to cold rolling and large deformation;

(5) cutting the final product into a circular sample for sensitization treatment;

(6) and (4) carrying out an oxalic acid solution electrolysis intergranular corrosion test on the sensitized ring sample.

2. The method for improving the corrosion resistance of the TP347HFG steel seamless steel pipe according to claim 1, wherein the method comprises the following steps: and (2) the size specification of the pierced billet subjected to hot rolling and punching in the step (1) is 92mm 14 m.

3. The method for improving the corrosion resistance of the TP347HFG steel seamless steel pipe according to claim 1, wherein the method comprises the following steps: the step (2) of primary solution treatment comprises the following steps: preserving the heat for 30-60 min at 1250-1280 ℃.

4. The method for improving the corrosion resistance of the TP347HFG steel seamless steel pipe according to claim 1, wherein the method comprises the following steps: and (3) rolling the steel pipe with the specification of 92mm x 14mm to perform large deformation, wherein the total deformation amount is more than 70%.

5. The method for improving the corrosion resistance of the TP347HFG steel seamless steel pipe according to claim 1, wherein the method comprises the following steps: and (4) carrying out three-stage secondary solution treatment, wherein the temperature in the solution heating furnace is divided into three zones: the temperature of the first zone is 800 ℃ and is kept for 30min, the temperature of the second zone is 1120 ℃ to 1180 ℃ and is kept for 80min, and the temperature of the third zone is 950 ℃ and is kept for 2 h.

6. The method for improving the corrosion resistance of the TP347HFG steel seamless steel pipe according to claim 1, wherein the method comprises the following steps: the sensitization treatment in the step (5) comprises the following steps: and (3) preserving the heat of the seamless steel pipe finished product subjected to solid solution at 700 ℃ for 2h for sensitization treatment.

7. The method for improving the corrosion resistance of the TP347HFG steel seamless steel pipe according to claim 1, wherein the method comprises the following steps: the test analysis in the step (5) specifically comprises the following steps:

1) observing the microscopic structure of the section by adopting an optical metallographic microscope, and measuring and calculating the grain size grade;

2) performing hardness test analysis by using a Brinell hardness tester;

3) using 10% oxalic acid solution at a current of 1A/cm²Etching for 90s, and observing intercrystalline corrosion by metallographic phase.

8. Use of a corrosion resistant TP347HFG steel seamless steel tube obtained according to the method of claim 1, characterized in that: the steel tube is applied to a boiler tube.

Technical Field

The invention belongs to the technical field of metal material modification, and particularly relates to a generation process method for improving corrosion resistance of a TP347HFG steel seamless steel pipe.

Background

The TP347HFG austenitic heat-resistant steel has excellent steam oxidation resistance and high-temperature strength, but in the temperature range of 400-850 ℃, Cr is a high-chromium carbide₂₃C₆And the crystal grain boundary is poor in chromium and intergranular corrosion is generated. The equipment or parts subjected to intergranular corrosion still have good and bright appearance, but the bonding force among crystal grains at the corroded parts is damaged, and the strength and the plasticity of the material are seriously reduced or lost. TP347HFG austenitic stainless steel, which suffered severe intergranular corrosion, was likely to crumble into powder with a light tap, although the appearance remained metallic. Therefore, it is of particular importance to improve the corrosion resistance of TP347HFG austenitic stainless steel.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: based on the technical problems pointed out in the background art, the invention provides a production process method for improving the corrosion resistance of a TP347HFG steel seamless steel pipe. Starting from the cooperative optimization of the production process of the TP347HFG austenitic stainless steel pipe, the remarkable effects of reducing the intergranular corrosion degree of the TP347HFG seamless steel pipe and improving the corrosion resistance are achieved on the premise of meeting the requirements of the structure and the mechanical property of the TP347HFG austenitic stainless steel pipe.

The technical scheme adopted by the invention for solving the technical problems is as follows: a method for improving corrosion resistance of a TP347HFG steel seamless steel tube comprises the steps of taking a pierced billet subjected to hot rolling and piercing as an original sample, carrying out high-temperature primary solution treatment to obtain a coarse-grain structure with fully dissolved niobium, carrying out cold rolling large deformation to fully refine coarse grains, and finally carrying out long-time three-stage secondary solution treatment on the seamless steel tube; and then testing the performance of the product after sensitization treatment, wherein the specific process steps are as follows:

(1) selecting a pierced billet obtained by hot piercing TP347HFG round steel as a sample; the original state steel is high-quality TP347HFG stainless steel, and the size specification of the pierced billet after hot rolling and perforation is 92mm x 14mm (outer diameter x wall thickness).

(2) Carrying out high-temperature primary solution treatment on the pierced billet; heating the sample to 1250-1280 ℃, and preserving heat for 30-60 min for primary solid solution.

(3) Carrying out cold rolling and large deformation on the pierced billet subjected to the primary solution treatment after water cooling and acid pickling; and (3) carrying out cold rolling large deformation on the sample with the specification of 92mm by 14mm by using a rolling mill, wherein the final cold rolling total deformation is more than 70%.

(4) Carrying out long-time three-section type secondary solution treatment on the steel pipe after the cold rolling and large deformation; namely, the solid solution heating furnace is divided into three subareas: the temperature of the first zone is 800 ℃ and is kept for 30min, the temperature of the second zone is 1120-1180 ℃ and is kept for 80min, and the temperature of the third zone is 950 ℃ and is kept for 2 h. The first zone adopts 800 ℃ to heat the steel pipe evenly and homogenize crystal grains to a certain degree, and the second zone adopts 1120 ℃ to refine the crystal grains and lead Cr to be refined₂₃C₆Fully dissolving, stabilizing treatment at 950 ℃ is adopted in the three zones, and the three aspects have comprehensive effects of refining grains and improving corrosion resistance.

(5) Cutting the final product into a circular sample for sensitization treatment; and (3) preserving the heat of the seamless steel pipe finished product subjected to solid solution at 700 ℃ for 2h for sensitization treatment.

(6) And (4) carrying out an oxalic acid solution electrolysis intergranular corrosion test on the sensitized ring sample.

The specific method for testing and analyzing the final product is as follows:

1) observing the microstructure by adopting an optical metallographic microscope, and calculating the grain size of the microstructure;

2) performing hardness test analysis by using a Brinell hardness tester;

3) using 10% oxalic acid solution at a current of 1A/cm²Etching for 90s, and observing intercrystalline corrosion by metallographic phase.

The invention has the beneficial effects that:

(1) the method provided by the invention obviously improves the intergranular corrosion resistance of the TP347HFG steel seamless steel tube.

(2) The invention creates the cooperative optimization of the seamless tube production process, in particular to the cooperative optimization of primary solution treatment, cold rolling large deformation and long-time three-section secondary solution treatment. Firstly, adopting high temperature one-time solution treatment to fully dissolve the niobium element in the structure; then cold rolling large deformation is carried out to fully refine coarse crystals formed by high-temperature solid solution; finally, the deformed crystal grains are homogenized through long-time three-stage secondary solution treatment, and simultaneously Cr precipitated along the grains is enabled to be uniform₂₃C₆Fully dissolved in the crystal grains, and the niobium carbide is precipitated again to meet the remarkable requirements of refining the crystal grains and improving the intercrystalline corrosion resistance.

The invention is further described below with reference to the accompanying drawings.

Drawings

FIG. 1 is a microstructure of TP347HFG steel after heat preservation at 1250 ℃ for 30min for one solution treatment (example 1).

FIG. 2 is a microstructure of TP347HFG steel after heat preservation at 1280 ℃ for 60min and one solution treatment (example 2).

FIG. 3 is a microstructure of TP347HFG steel after heat preservation at 1250 ℃ for 30min and 60% deformation and after heat preservation at 1120 ℃ for 20min for secondary solution treatment (comparative example 1).

FIG. 4 is a microstructure of TP347HFG steel after heat preservation at 1250 ℃ for 30min and after 70% deformation and after heat preservation at 1120 ℃ for 80min for two solution treatments (comparative example 3).

FIG. 5 is a microstructure diagram of a TP347HFG steel sample after heat preservation at 1250 ℃ for 30min for one time of solution treatment, 60% deformation of the sample, and three-stage solution treatment at 800 ℃, 1120 ℃ and 950 ℃ (comparative example 2).

FIG. 6 is a microstructure of TP347HFG steel after heat preservation at 1250 ℃ for 30min for one time solution treatment, sample deformation of 70% and three-stage solution treatment at 800 ℃, 1120 ℃ and 950 ℃ (example 1).

FIG. 7 is a microstructure diagram of an intergranular corrosion of TP347HFG steel after 1250 ℃ heat preservation for 30min, one-time solution treatment, 60% deformation and 1120 ℃ heat preservation for 20min, sensitization treatment at 700 ℃ for 2h, and electrolysis with 10% oxalic acid solution (comparative example 1).

FIG. 8 is a microstructure diagram of an intergranular corrosion of TP347HFG steel after heat preservation at 1250 ℃ for 30min, 70% deformation of a sample, three-stage solution treatment at 800 ℃, 1120 ℃ and 950 ℃, 2h sensitization at 700 ℃ and 10% oxalic acid solution electrolysis (example 1).

FIG. 9 is a microstructure diagram of an intergranular corrosion of TP347HFG steel after being subjected to primary solution treatment at 1250 ℃ for 30min, deformation of 70% and heat preservation at 1120 ℃ for 80min, being sensitized at 700 ℃ for 2h and then being subjected to electrolysis by using a 10% oxalic acid solution (comparative example 3).

FIG. 10 is a microstructure diagram of intergranular corrosion of TP347HFG steel after heat preservation at 1250 ℃ for 30min, 70% deformation of a sample, three-stage solution treatment at 800 ℃, 1120 ℃ and 950 ℃, 2h sensitization at 700 ℃ and 10% oxalic acid solution electrolysis (comparative example 4).

Detailed Description

The invention will now be further illustrated by reference to specific examples, which are intended to be illustrative of the invention and are not intended to be a further limitation of the invention.