WO2015109552A1

WO2015109552A1 - Stainless steel seamless pipe

Info

Publication number: WO2015109552A1
Application number: PCT/CN2014/071435
Authority: WO
Inventors: 吴津宁
Original assignee: 吴津宁
Priority date: 2014-01-25
Filing date: 2014-01-25
Publication date: 2015-07-30

Abstract

A stainless steel seamless pipe, comprising the following components by weight percentage: 0.07%-0.09% of C, 1.1%-1.3% of Mn, 18.2%-18.5% of Ni, 21.1%-21.3% of Cr, 0.35%-0.37% of Nb, 0.14%-0.16% of Si, 0.2%-0.4% of N, ≤0.2% of Cu, ≤0.015% of S, ≤0.025% of P, 0.17%-0.19% of Mo, 1.1%-1.3% of Al, 0.7%-0.9% of Ti, 0.015%-0.017% of V, 1.5%-1.8% of a composite rare earth, and the balance being Fe.

Description

TECHNICAL FIELD The present invention relates to a stainless steel seamless steel pipe, and in particular to a stainless steel seamless steel pipe used for a sulfuric acid waste heat recovery device. BACKGROUND OF THE INVENTION Stainless steel seamless steel pipe is a common metallurgical metal product, and the seamless steel pipe is a circular, square, rectangular steel having a hollow section and no seam at the periphery. Seamless steel tubes are made of steel ingots or solid tube blanks, which are then hot rolled, cold rolled or cold drawn. The seamless steel pipe has a hollow section and is used in a large amount as a pipe for conveying fluid. At present, the steel pipe used in the residual heat reflux device of sulfuric acid on the market, ordinary carbon steel does not have corrosion resistance at all, generally can only corrode perforation in a few months, while austenitic stainless steel 310S has better resistance to pitting and pitting. And uniform corrosion performance, but due to the extremely poor stress corrosion resistance of austenitic stainless steel, it is limited to use in this environment. Due to its special environmental requirements, it must have good corrosion resistance, pitting corrosion resistance, high temperature resistance and stress resistance. Although ordinary steel pipes can basically meet the requirements, the overall performance is not ideal, and pitting corrosion and grain boundaries are easy to occur. Corrosion results in a decrease in the mechanical strength and elongation of the steel tube, resulting in a shorter service life of the steel tube and a higher price. SUMMARY OF THE INVENTION The technical problem to be solved by the present invention is to provide a superior resistance to intergranular corrosion, high tensile strength and high yield strength, small surface roughness, and good in view of the above disadvantages of the prior art. The surface quality and size of the stainless steel pipe used for the sulfuric acid waste heat recovery device. The technical solution of the present invention to solve the above technical problems is: A stainless steel seamless steel pipe comprising the following components by weight: C: 0.07-0.09%, Mn: 1.1-1.3%, Ni: 18.2-18. 5% , Cr: 21.1-21·3%, Nb: 0.35-0·37%, Si: 0.14-0·16%, N: 0.2-0.4%, Cu: 0.15-0.17%, 0.015%, P ^ 0.025%, Mo : 0· 17- 0· 19%, Al: 1.1.3%, Ti _: 0·7-0.9%, V: 0.015-0.017%, composite rare earth: 1.5-1.8%, balance is Fe , among them: In the composite rare earth, the following components are included by weight: 镧: 25-40%, 铈: 13-15%, 镨: 15-18%, 镝: 11-14%, 钬: 5-8%, , L: 8-10%, 钇: 8-10%, the sum of the above composite rare earth components is 100%; stainless steel seamless steel pipe is prepared as follows:

(1) The outer diameter of the tube is determined by the pick-up and the content of the raw material tube after the pickling and solution treatment, and the cold-rolling equipment is cold-rolled to the outer tube and the wall thickness of the tube. , wall thickness error is ± 0 · 12mm _;

(2) heat-treating the intermediate tube obtained in the step (1) at a temperature of 960 ° C - 980 ° C for 20-25 min, and then cooling to room temperature by combining water cooling and air cooling;

(3) further cold-drawing the intermediate tube blank after the heat treatment in step (2) to the middle semi-finished tube with the outer diameter and wall thickness of the required tube, the outer diameter error of the tube is ± 25 mm, and the wall thickness error is ± 15 mm;

(4) The wall thickness error is ± 0. 01mm; the wall thickness error is ± 0. 01mm; the wall thickness error is ± 0. 01mm;

(5) Pickling and passivation of the finished straight pipe at a temperature of 45-55 ° C using 10%-14% by mass of nitric acid and 4%-6% by mass of hydrofluoric acid. The inner wall of the pipe is used successively. The cotton cloth and the dry cotton cloth soaked in acetone are cleaned by multiple times of wiping by the pressure of the high pressure water gun, and the outer wall of the tube is directly wiped with acetone cotton cloth and dry cotton cloth for cleaning;

(6) Performing a bright atmosphere heat treatment on the cleaned straight pipe by a pure nitrogen atmosphere, the heat treatment temperature is 1130 ° C - 1160 ° C, the heat treatment time is 25-30 min, and then air cooled to room temperature;

(7) bending the finished straight pipe processed by the step (5) by using the interference radial pressing method to obtain a U-shaped pipe with a thin wall, a seamless, elliptical ellipse;

(8) The solution heat treatment of the elbow portion of the U-shaped tube after the step (7) is treated, and then the nitric acid having a mass percentage of 10%_14% and the hydrofluoric acid having a mass percentage of 4%-6% are used. The elbow portion is pickled and passivated at 45-55 ° C, and finally the entire finished tube is straightened;

(9) Non-destructive testing of the finished pipe after straightening treatment, after the inspection is passed, the finished pipe shall be rust-proofed. Then package it into the library. The technical solution further defined by the present invention is as follows: the above-mentioned stainless steel seamless steel pipe has an inner and outer surface roughness of 1. 6 μ π ΐ, a tensile yield strength at room temperature of ^260 ΜΡ, a tensile strength of 5403⁄4^, an elongation of 50%, and a hardness of 90 HRB. 5-2. 0MP。 The pressure of the high pressure water gun is 1. 5-2. 0MP. The cooling of the water is cooled by the water cooling with a water cooling of 3. 4-3. 7 ° C / s cooling, after the heat treatment, the water cooling and the air cooling combined with the water cooling to 3. 4-3. 7 ° C / s cooling Rate the intermediate tube blank to 400-420 ° C, then air cooled to 250-300 ° C, and then use water cooling to cool the intermediate tube blank to 150-180 ° at a cooling rate of 2. 3-2. 5 ° C / s. C, finally air cooled to room temperature. The beneficial effects of the invention are:

(1) The alloy element of the composition of the stainless steel seamless steel pipe of the present invention is selectively added as follows: Cr: 24. 0-26. 0%, Nb: 0. 45-0. 60%, and v: 0. 0018- 0. 0022%, etc., where:

The addition of Cr mainly increases the hardenability of the stainless steel seamless steel pipe, and significantly improves the strength, hardness and wear resistance, which also increases the corrosion resistance and oxidation resistance;

The affinity between Nb and C is relatively large, and Nb is added to give priority to C-bonding to form niobium carbide (NbC), which effectively prevents intergranular corrosion;

The addition of Nb and V: a. When the temperature gradually decreases during the rolling, the solubility products of carbon and nitride of Nb and V in austenite decrease, and the deformation induces precipitation, and carbon and nitrogen The precipitate diffuses before the transformation of austenite to ferrite, and becomes a nucleating agent of ferrite. The ferrite is formed in a large amount under a small degree of subcooling, and it is difficult to grow, thereby refining the ferrite crystal. Grain, increase yield strength and tensile strength; b. Add Nb, V- to increase the strength while reducing carbon equivalent content. On the other hand, fix impurities such as oxygen, sulfur, etc. to improve seamless steel pipe Solderability.

(2) adding an appropriate amount of composite rare earth elements to the components of the stainless steel seamless steel pipe of the present invention, by weight The fractions include the following components, 镧: 25-40%, 铈: 13-15%, 镨: 15-18%, 镝: 11-14%, 钬: 5-8%, 钆: 8-10%, 钇: 8-10%, the sum of the above components is 100%; Since the above rare earth elements have a large metal atomic radius and the rare earth has high activity, it is easy to fill in the crystal grains and defects thereof, and can form crystal grains. The film continues to grow, thereby refining the grain and improving the performance of the steel. At the same time, the rare earth element is easily combined with an element such as oxygen or sulfur to form a compound having a high melting point, which can purify the steel.

(3) The invention adopts three cold rolling in the rolling process, can effectively prevent the uneven deformation of the steel pipe, and produces the steel pipe with small outer diameter and wall thickness error, high precision, good surface quality and smoother.

(4) In the preparation step (5) of the stainless steel seamless steel pipe of the present invention, the mass percentage is 10%-14% of nitric acid and the mass percentage is 4%-6% of hydrofluoric acid at 45-55 ° C. The tube is pickled and passivated to clean the surface of the steel tube, smooth the surface, and control the steel tube without being pickled.

(5) The invention is cold-rolled out of a straight pipe with a thin wall, and is subjected to multi-pass pickling, degreasing, and atmospheric bright heat treatment, and then bent into a U-shaped seamless stainless steel tube by using an interference radial pressing method. The inner wall of the U-shaped seamless stainless steel tube is clean, non-oxidizing, and the elbow is elliptical, which not only improves the quality of the steel pipe, but also meets the requirements for the use of the sulfuric acid waste heat recovery device.

(6) In the present invention, the cleaned treated tube is subjected to an atmospheric bright heat treatment using a pure nitrogen atmosphere, the heat treatment temperature is 1130 ° C - 1160 ° C, the heat treatment time is 25-30 min, and then air cooled to room temperature; The bright heat treatment process not only prevents the precipitation of carbides in the intergranular layer, but also prevents carburization and nitriding during the heat treatment process, thereby ensuring the corrosion resistance of the material;

(7) The stainless steel pipe of the present invention can pass the intergranular corrosion test of sulfuric acid-copper sulfate by ASTM A262E method, and can test the residual stress of the straight pipe and the bent pipe, and has excellent corrosion resistance; likewise, the invention is limited by composition and process parameters. The stainless steel pipe not only has better corrosion resistance, but also the inner and outer surface roughness, yield strength and tensile strength of the stainless steel seamless steel pipe of the invention are high, both reach and exceed the international standard level, and the inner and outer surface roughness 1 6 μ πι, tensile yield strength at room temperature 260 ΜΡ, tensile strength ^ 540 ΜΡ, elongation 50%, hardness 90 HRB. detailed description Example 1 The stainless steel seamless steel pipe of this example has a weight percentage of the components: C: 0.07%, Mn: 1.1%, Ni: 18. 2%, Cr: 21. 1%, Nb: 0. 35%, Si: 0. 14%, N: 0. 2%, Cu _: 0. 15%, S: 0. 015%, P: 0. 025%, Mo: 0. 17%, Al : 1 1%, Ti: 0.7%, V: 0.15%, composite rare earth: 1. 5%, balance is Fe, the weight percentage of composite rare earth components is: 镧: 30%, 铈: 14%,镨: 16%, 镝: 13%, iron: 7%, 钆: 10%, 钇: 10%. The stainless steel seamless steel pipe of this embodiment is prepared as follows:

(2) The intermediate tube blank obtained in the step (1) is heat-treated at a temperature of 960 ° C for 22 minutes, and then the intermediate tube blank is cooled to 420 ° C by water cooling at a cooling rate of 3. 4 ° C / s. , then air cooled to 300 ° C, and then cooled by water cooling at a cooling rate of 2. 3 ° C / s to 150 ° C, and finally air cooled to room temperature;

(5) Acidizing and passivating the finished straight pipe at a temperature of 45 °C using 13% by mass of nitric acid and 4% by mass of hydrofluoric acid. The inner wall of the tube is made of cotton cloth and dry cotton cloth soaked in acetone. 5MP; The pressure of the high pressure water gun is 1. 5MP;; the pressure of the high pressure water gun is 1. 5MP;

(6) The cleaned and treated finished straight pipe is subjected to an atmospheric bright heat treatment using a pure nitrogen atmosphere, the heat treatment temperature is 1130 ° C, the heat treatment time is 26 min, and then air-cooled to room temperature;

(7) bending the finished straight pipe processed by the step (5) by using the interference radial pressing method to obtain a U-shaped pipe with a thin wall, a seamless shape and a good elbow ellipse; (Λ) solution heat treatment of the elbow portion of the sickle tube after the step (7) treatment, and then using 13% by mass of nitric acid and 4% by mass of hydrofluoric acid at 45 ° C The picking and passivation treatment is performed on the elbow portion, and finally the entire finished tube is straightened;

(9) Non-destructive testing of the finished pipe after straightening treatment, after the inspection is passed, the finished pipe is rust-proofed, and then packaged into the warehouse. In the present embodiment, the stainless steel seamless steel pipe has an inner and outer surface roughness of 1.4 μm, a tensile yield strength of 270 Å at room temperature, a tensile strength of 620 Å, an elongation of 60%, and a hardness of 80 HRB. Example 2 The stainless steel seamless steel pipe of this example has a weight percentage of components: C: 0.08%, Mn: 1.2%, Ni: 18.3%, Cr: 21.2%, Nb: 0.36%, Si: 0.15%, N: 0.3%, Cu: 0.16%, S: 0.013%, P: 0.021%, Mo: 0.18%, Al: 1.2%, Ti: 0.8%, V: 0.016%, composite rare earth: 1.7%, balance For Fe, the weight percentage of the composite rare earth component is: 镧: 29%, 铈: 15%, 镨: 18%, 镝: 14%, iron: 8%, 钆: 8%, 钇: 8%. The stainless steel seamless steel pipe of this embodiment is prepared as follows:

(1) The outer diameter of the tube is determined by the pick-up and the content of the raw material tube after the pickling and solution treatment, and the cold-rolling equipment is cold-rolled to the outer tube and the wall thickness of the tube. , the wall thickness error is ±0·12mm _;

(2) The intermediate tube obtained in the step (1) is heat-treated at a temperature of 980 ° C for 25 minutes, and then the intermediate tube blank is cooled to 410 ° C by water cooling at a cooling rate of 3.7 ° C / s, and then Air cooling to 280 ° C, and then using water cooling to cool the intermediate tube blank to 180 ° C at a cooling rate of 2.5 ° C / s, and finally air cooled to room temperature;

(3) Step (2) The intermediate tube blank after heat treatment is further cold-drawn to the middle semi-finished tube of the required tube outer diameter and wall thickness, the tube outer diameter error is ±25 mm, and the wall thickness error is ±15 mm;

(4) straightening the intermediate semi-finished pipe directly through the cold rolling equipment to the finished product with the outer diameter and wall thickness of the pipe Tube, tube outer diameter error is ±0.08mm, wall thickness error is ±0.01mm;

(5) Picking and passivating the finished straight pipe at 50 °C with 10% by mass of nitric acid and 6% by mass of hydrofluoric acid. The inner wall of the pipe is made of cotton cloth and dry cotton cloth soaked in acetone. The cleaning process is carried out by multiple times of wiping by the pressure of the high pressure water gun, and the outer wall of the tube is directly wiped with acetone cotton cloth and dry cotton cloth for cleaning, and the pressure of the high pressure water gun is 1.8 MP;

(6) Performing a bright atmosphere heat treatment on the cleaned straight pipe by a pure nitrogen atmosphere, the heat treatment temperature is 1160 ° C, the heat treatment time is 25 min, and then air-cooled to room temperature;

(8) solution heat treatment of the elbow portion of the U-shaped tube treated by the step (7), and then using 10% by mass of nitric acid and 6% by mass of hydrofluoric acid at 50 ° C The picking and passivation treatment is performed on the elbow portion, and finally the entire finished tube is straightened;

(9) Non-destructive testing of the finished pipe after straightening treatment, after the inspection is passed, the finished pipe is rust-proofed, and then packaged into the warehouse. In the present embodiment, the stainless steel seamless steel pipe has an inner and outer surface roughness of Ι.Ομπι, a room temperature tensile yield strength of 300 ΜΡ, a tensile strength of 580 Å, an elongation of 65%, and a hardness of 70 HRB. Example 3 The stainless steel seamless steel pipe of this example has a weight percentage of components: C: 0.09%, Mn: 1.3%, Ni: 18.5%, Cr: 21.3%, Nb: 0.37%, Si: 0.16%, N: 0.4%, Cu: 0.17%, S: 0.011%, P: 0.025%, Mo: 0.19%, Al: 1.3%, Ti: 0.9%, V: 0.017%, composite rare earth: 1.8%, The balance is Fe, and the weight percentage of the composite rare earth component is: 镧: 38%, 铈: 13%, 镨: 15%, 镝: 11%, iron: 5%, 钆: 9%, 钇: 9%. The stainless steel seamless steel pipe of this embodiment is prepared as follows:

(1) The outer diameter of the tube is determined by the pick-up and the content of the raw material tube after the pickling and solution treatment, and the cold-rolling equipment is cold-rolled to the outer tube and the wall thickness of the tube. , wall thickness error is ± 0· 12mm _;

(2) The intermediate tube blank obtained in the step (1) is heat-treated at a temperature of 970 ° C for 20 minutes, and then the intermediate tube blank is cooled to 400 ° C by water cooling at a cooling rate of 3.5 ° C / s. , then air cooled to 250 ° C, and then cooled by water cooling at a cooling rate of 2. 4 ° C / s to 160 ° C, and finally air cooled to room temperature;

(5) The raw pipe is pickled and passivated at a temperature of 55 ° C using 14% by mass of nitric acid and 5% by mass of hydrofluoric acid. The inner wall of the pipe is made of cotton cloth and dry cotton cloth soaked in acetone. The cleaning process is carried out by multiple times of wiping by the pressure of the high pressure water gun, and the outer wall of the tube is directly wiped and cleaned with acetone cotton cloth and dry cotton cloth, and the pressure of the high pressure water gun is 2MP;

(6) The cleaned and treated finished straight pipe is subjected to an atmospheric bright heat treatment using a pure nitrogen protective atmosphere, the heat treatment temperature is 1150 ° C, the heat treatment time is 30 min, and then air-cooled to room temperature;

(8) solution heat treatment of the elbow portion of the U-shaped tube after the step (7), and then using 14% by mass of nitric acid and 5% by mass of hydrofluoric acid at 55 ° C The picking and passivation treatment is performed on the elbow portion, and finally the entire finished tube is straightened;

(9) Non-destructive testing of the finished pipe after straightening treatment, after the inspection is passed, the finished pipe is rust-proofed, and then packaged into the warehouse. In this embodiment, the stainless steel seamless steel pipe has an inner and outer surface roughness of 0.99 μm, a room temperature tensile yield strength of 280 ΜΡ, a tensile strength of 600 ΜΡ, an elongation of 55%, and a hardness of 75 HRB. Other than the above-described embodiments, the present invention may have other embodiments. Equivalent substitution or equivalent change The technical solutions formed are all within the scope of protection required by the present invention ₍

Claims

O 2015/109552 Claims PCT/CN2014/071435

A stainless steel seamless steel pipe characterized by comprising the following components by weight: C: 0.07-0.09%, Mn: 1.1-1.3%, Ni: 18.2-18.5%, Cr: 21.1-21.3%, Nb : 0.35-0.37%, Si: 0.14-0.16%, Ν: 0·2 - 0.4%, Cu: 0.15-0.17%, 0.015%, P ^ 0.025%, Mo: 0· 17- 0· 19%, A1: L 1-1.3%, Ti: 0·7-0.9%, V: 0.015-0.017%, composite rare earth: 1.5-1.8%, balance is Fe, wherein: the composite rare earth, by weight percentage Including the following components: 镧: 25-40%, 铈: 13-15%, 镨: 15-18%, 镝: 11-14%, 钬: 5-8%, , L: 8-10%, 钇: 8-10%, the sum of the above composite rare earth components is 100%; the stainless steel seamless steel pipe is prepared as follows:

(3) further cold-drawing the intermediate tube blank after the heat treatment in step (2) to the middle semi-finished tube with the required outer diameter and wall thickness of the tube, the outer diameter error of the tube is ±25 mm, and the wall thickness error is ±15 mm;

(4) The middle semi-finished pipe is directly passed through the cold rolling equipment to the finished straight pipe of the required pipe outer diameter and wall thickness, the pipe outer diameter error is ±0.08 mm, and the wall thickness error is ±0.01 mm;

(7) bending the finished straight pipe after the step (5) by using the interference radial pressing method to obtain a thin wall, Seamless, elliptical elliptical good u-shaped tube;

(8) The solution heat treatment of the elbow portion of the U-shaped tube after the step (7) is treated, and then the nitric acid having a mass percentage of 10% to 14% and the hydrogen fluoride having a mass percentage of 4% to 6% are used. The acid is pickled and passivated at 45-55 ° C, and finally the entire finished tube is straightened;

(9) Non-destructive testing of the finished pipe after straightening treatment, after the inspection is passed, the finished pipe is rust-proofed, and then packaged into the warehouse.

The stainless steel seamless steel pipe according to claim 1, wherein: the stainless steel seamless steel pipe has an inner and outer surface roughness of 1.6 μπι, a room temperature tensile yield strength of 260 ΜΡ, a tensile strength of 5403⁄4^, an elongation of 50%, and a hardness. 90HRB.

3. The stainless steel seamless steel pipe according to claim 1, wherein: in the step (5) of the preparation process of the stainless steel seamless steel pipe, the pressure of the high pressure water gun is 1. 5 when the cleaning process is performed by means of high pressure water gun pressure pushing. -2.0MP.

4. The stainless steel seamless steel pipe according to claim 1, wherein: in the step (2) of the preparation process of the stainless steel seamless steel pipe, after the heat treatment, water cooling and air cooling are combined and cooled, and the water cooling and air cooling are combined. Water cooling The intermediate tube blank is cooled to 400-420 ° C at a cooling rate of 3.4-3.7 ° C / s, then air cooled to 250-300 ° C, and then cooled by water cooling at a cooling rate of 2.3-2.5 ° C / s. The billet is cold to

150-180 ° C, finally air cooled to room temperature.