CN111057830A

CN111057830A - Method for manufacturing large-caliber thick-wall seamless hot-pressing reducing pipe of 630 ℃ ultra-supercritical unit G115 and reducing pipe

Info

Publication number: CN111057830A
Application number: CN201911251001.2A
Authority: CN
Inventors: 高砚松; 高峰; 高文兴; 程万林; 于敏英; 高学英; 高绍亮; 张智博; 李维民
Original assignee: Hebei Yadu Pipeline Equipment Group Co ltd
Current assignee: Hebei Yadu Pipeline Equipment Group Co ltd
Priority date: 2019-12-09
Filing date: 2019-12-09
Publication date: 2020-04-24

Abstract

The application relates to the technical field of metal material processing. The application discloses a manufacturing method of a large-caliber thick-wall seamless hot-pressing reducing pipe of a 630 ℃ ultra-supercritical unit G115, which comprises the steps of pressing and processing a pipe blank of a straight pipe to obtain a prefabricated reducing pipe; the pipe blank of the straight pipe is a 630 ℃ ultra supercritical unit G115 large-caliber thick-wall seamless steel pipe; and carrying out heat treatment on the prefabricated reducing pipe to obtain the reducing pipe. The method for manufacturing the large-caliber thick-wall seamless reducing pipe aims at the large-caliber thick-wall seamless steel pipe of the 630 ℃ ultra-supercritical unit G115, and the manufactured reducing pipe is good in mechanical property, uniform in size, uniform in thickness and free of defects in appearance. The method can be applied to different fields of ultra-supercritical boilers, four pipelines of power stations and the like.

Description

Method for manufacturing large-caliber thick-wall seamless hot-pressing reducing pipe of 630 ℃ ultra-supercritical unit G115 and reducing pipe

Technical Field

The application relates to the technical field of metal material processing, for example to a method for manufacturing a large-caliber thick-wall seamless hot-pressing reducing pipe of a 630 ℃ ultra-supercritical unit G115 and the reducing pipe.

Background

At present, the mechanical property at room temperature, the impact property, the mechanical property at high temperature and the durability of the G115 steel are all higher than those of the P92 steel in GB5310 and ASME standard, so the forming research on the G115 steel is increasingly increased. Wherein, a patent discloses a preparation method of a large-caliber thick-wall seamless steel pipe of a 630 ℃ ultra-supercritical unit G115. In the process of implementing the embodiments of the present disclosure, it is found that at least the following problems exist in the related art: in the prior art, the research on the manufacture of the reducing pipe aiming at the large-diameter thick-wall seamless steel pipe is not yet carried out.

Disclosure of Invention

The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosed embodiments. This summary is not an extensive overview nor is intended to identify key/critical elements or to delineate the scope of such embodiments but rather as a prelude to the more detailed description that is presented later.

The embodiment of the disclosure provides a method for manufacturing a large-caliber thick-wall seamless hot-pressing reducing pipe of a 630 ℃ ultra-supercritical unit G115 and the reducing pipe, and aims to solve the technical problem that the reducing pipe manufacturing is not performed on the large-caliber thick-wall seamless steel pipe in the prior art.

In some embodiments, the method of manufacturing a reducing pipe comprises the steps of:

pressing and processing the tube blank of the straight tube to obtain a prefabricated reducing tube; the pipe blank of the straight pipe is a 630 ℃ ultra supercritical unit G115 large-caliber thick-wall seamless steel pipe;

carrying out heat treatment on the prefabricated reducing pipe to obtain a finished reducing pipe product, and finishing the manufacturing of the reducing pipe;

wherein the heat treatment comprises: heating the prefabricated reducing pipe to 1050-1100, then carrying out primary temperature equalization, carrying out primary heat preservation, and then carrying out primary cooling to room temperature to obtain the reducing pipe subjected to primary heat treatment;

and heating the reducing pipe subjected to the primary heat treatment to 750-820 heads, then carrying out secondary temperature equalization, carrying out secondary heat preservation, and then carrying out secondary cooling to room temperature.

In some embodiments, the reducing pipe is manufactured by the manufacturing method.

The method for manufacturing the reducing pipe and the reducing pipe provided by the embodiment of the disclosure can realize the following technical effects:

the manufacturing method provided by the embodiment of the disclosure is a method for manufacturing a large-caliber thick-wall seamless reducing pipe aiming at a 630 ℃ ultra-supercritical unit G115 large-caliber thick-wall seamless steel pipe, and is obtained by deeply researching various parameters of the G115 large-caliber thick-wall seamless steel pipe. The thickness of the manufactured reducing pipe wall is uniform, the size of the product reaches the standard, and the defects of small outer diameter, small inner diameter and small internal through flow area caused by expansion with heat and contraction with cold are avoided. Moreover, the appearance is flawless, and the mechanical property is good. The method can be applied to different fields of ultra-supercritical boilers, four pipelines of power stations and the like.

The foregoing general description and the following description are exemplary and explanatory only and are not restrictive of the application.

Drawings

One or more embodiments are illustrated in the accompanying drawings, which correspond to the accompanying drawings, and which do not constitute a limitation on the embodiments, in which elements having the same reference number designation are shown as similar elements, and in which:

FIG. 1 is a schematic structural diagram of a straight pipe blank in a manufacturing method provided by an embodiment of the disclosure;

fig. 2 is a schematic view of a press forming process of a prefabricated reducing pipe in a manufacturing method according to an embodiment of the disclosure;

FIG. 3 is a schematic diagram of a press forming process in a manufacturing method provided by an embodiment of the disclosure;

fig. 4 is a schematic structural diagram of a reducing pipe obtained by a manufacturing method provided by an embodiment of the disclosure;

FIG. 5 is a microstructure of a reducer I provided by an embodiment of the disclosure;

FIG. 6 is a grain size diagram of a reducer I provided by an embodiment of the present disclosure;

FIG. 7 is a microstructure view of a reducer II provided by an embodiment of the present disclosure;

FIG. 8 is a grain size diagram of a reducer II provided by an embodiment of the present disclosure;

reference numerals:

10: a straight pipe blank; 11. prefabricating a reducing pipe; 111. a first large-diameter end; 112. a first small-caliber end; 20. finishing the reducing pipe; 21. a second large-diameter end; 22. a second small-caliber end; 31. a lower die; 32. and (4) an upper die.

Detailed Description

So that the manner in which the features and elements of the disclosed embodiments can be understood in detail, a more particular description of the disclosed embodiments, briefly summarized above, may be had by reference to the embodiments, some of which are illustrated in the appended drawings. In the following description of the technology, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the disclosed embodiments. However, one or more embodiments may be practiced without these details. In other instances, well-known structures and devices may be shown in simplified form in order to simplify the drawing.

In this document, it is to be understood that relational terms such as first (or first) and second, and the like (or second) are used solely to distinguish one entity or structure from another entity or structure without necessarily requiring or implying any actual such relationship or order between such entities or structures.

In this document, it is to be understood that the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated in the drawings for convenience in describing the present disclosure and to simplify the description, but are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the present disclosure.

In this document, unless otherwise specified and limited, it is to be understood that the terms "mounted," "connected," and "connected" are used broadly and may be, for example, mechanically or electrically connected, or may be connected through two elements, directly or indirectly through an intermediate medium, and those skilled in the art will understand the specific meaning of the terms as they are used in a specific situation.

The embodiment of the disclosure provides a method for manufacturing a large-caliber thick-wall seamless hot-pressing reducing pipe of a 630 ℃ ultra-supercritical unit G115. As described in connection with fig. 1 to 4, the manufacturing method includes the steps of:

s10, pressing and processing the tube blank of the straight tube to obtain a prefabricated reducing tube; the pipe blank of the straight pipe is a 630 ℃ ultra supercritical unit G115 large-caliber thick-wall seamless steel pipe;

s20, carrying out heat treatment on the prefabricated reducing pipe to obtain a reducing pipe, and finishing the manufacturing of the reducing pipe;

wherein the heat treatment comprises: heating the prefabricated reducing pipe to 1050-1100 ℃, then carrying out primary temperature equalization, carrying out primary heat preservation, and then carrying out primary cooling to room temperature to obtain the reducing pipe subjected to primary heat treatment;

and heating the reducing pipe subjected to the primary heat treatment to 750-820 ℃, then carrying out secondary temperature equalization, carrying out secondary heat preservation, and then carrying out secondary cooling to room temperature.

The manufacturing method of the embodiment of the disclosure aims at manufacturing a large-caliber thick-wall seamless reducer of a 630 ℃ ultra-supercritical unit G115. The term "large-diameter thick wall" is used as a general term for those skilled in the art, and may include, for example, an outer diameter of 325 to 1200mm and a wall thickness of 20 to 180 mm.

In some embodiments, the wall thickness of the straight tube blank is greater than or equal to 20% of its outer diameter. Optionally, the wall thickness of the straight pipe blank is 20% to 30% of its outer diameter.

In the embodiment of the disclosure, the 630 ℃ ultra-supercritical unit G115 large-caliber thick-wall seamless steel pipe can be purchased, or manufactured by the method disclosed in the patent document with publication number CN 108998650A and invented name of "630 ℃ ultra-supercritical unit G115 large-caliber thick-wall seamless steel pipe manufacturing method". Due to the large caliber and the thick wall of the steel pipe, when the reducing pipe product is manufactured, the reducing pipe product is easy to be small in outer diameter, inner diameter and inner through flow area due to expansion with heat and contraction with cold after being pressed. Therefore, the manufacture of the prefabricated reducing pipe also affects the size, appearance and the like of the finished reducing pipe to some extent.

In some embodiments, in step S10, the straight tube blank is press-worked to obtain a prefabricated reducing tube; the method comprises the following steps:

s11, heating the tube blank of the straight tube, and then performing compression molding to obtain a prefabricated reducing tube; wherein the heating temperature is 1100-1200 ℃.

Of course, the manner of obtaining the prefabricated reducing pipe is not limited to the aforementioned steps.

In this embodiment, the press forming of the prefabricated reducing pipe may be performed by using a conventional press die. Wherein, the inner diameter of the large-diameter end of the pressing die is consistent with the outer diameter R' of the straight tube blank. As shown in fig. 3, the prefabricated reducing pipe 11 obtained by heating and pressing includes a large-caliber end (denoted as a first large-caliber end 111) and a small-caliber end (denoted as a first small-caliber end 112), and correspondingly, as shown in fig. 4, the finished reducing pipe 20 also includes a large-caliber end (denoted as a second large-caliber end 21) and a small-caliber end (denoted as a second small-caliber end 22). In consideration of the dimensional difference caused by the expansion and contraction with heat and the subsequent heat treatment process, the outer diameter R of the large-caliber end of the finished reducing pipe 20 can be set more accurately by controlling the outer diameter R' of the straight pipe blank.

In some embodiments, the outer diameter R 'of the straight pipe blank is 1-1.03 times of the outer diameter R' of the large-caliber end of the prefabricated reducing pipe; and the outer diameter R' of the large-caliber end of the prefabricated reducing pipe is 1-1.03 times of the outer diameter R of the large-caliber end of the finished reducing pipe. And controlling the ratio relation between the outer diameter R 'of the straight pipe blank, the outer diameter R' of the large-diameter end of the prefabricated reducing pipe and the outer diameter R of the large-diameter end of the finished reducing pipe product 20, so as to obtain the outer diameter R of the large-diameter end of the finished reducing pipe product 20 which is set more accurately. The deformation rate can be controlled, the outer diameter, the inner diameter and the inner through flow area of the obtained reducing pipe can be effectively ensured to reach the standard, the wall thickness is uniform and transitional, and the appearance is flawless.

Optionally, the outer diameter R 'of the straight pipe blank is 1-1.02 times of the outer diameter R' of the large-caliber end of the prefabricated reducing pipe; and the outer diameter R' of the large-caliber end of the prefabricated reducing pipe is 1-1.02 times of the outer diameter R of the large-caliber end of the finished reducing pipe.

Optionally, the outer diameter R' of the straight pipe blank is 1.01 times the outer diameter R ″ of the large-caliber end of the prefabricated reducing pipe; and the outer diameter R' of the large-diameter end of the prefabricated reducing pipe is 1.01 times of the outer diameter R of the large-diameter end of the finished reducing pipe.

In the embodiment of the disclosure, the outer diameter of the small-caliber end of the finished reducing pipe is not limited, and the reducing pipe is formed by pressing according to actual needs. When the difference between the outer diameter R of the small-caliber end of the finished product of the reducing pipe and the outer diameter R of the large-caliber end is larger, a multi-stage pressing deformation forming process can be adopted.

In the embodiment of the present disclosure, in step S11, the straight tube blank needs to be heated and then subjected to press forming, and the heating temperature affects the deformation rate of the pressing process to a certain extent, so the temperature is controlled to be in the range of 1100 ℃ to 1200 ℃.

In some embodiments, the heating temperature in step S11 is 1120-1160 ℃. Optionally, the heating temperature is 1130 ℃ to 1150 ℃. Alternatively, the heating temperature is 1140 ℃. The more accurate the temperature control, the more advantageous the control of the obtained outer diameter values of the large-diameter end and the small-diameter end of the preset reducing pipe.

In step S11, the straight tube blank is heated to a temperature in the range of 1100 ℃ to 1200 ℃ and is subjected to heat preservation for a certain time before being subjected to press forming, and the heat preservation time is not limited and is determined according to parameters such as the wall thickness of the straight tube blank. Alternatively, the straight pipe blank is heated and then is subjected to heat preservation for 1 to 2 hours, and then is subjected to press forming.

In the embodiment of the present disclosure, in step S20, the heat treatment on the prefabricated reducing pipe includes two heat treatments, where one heat treatment is a normalizing heat treatment or a quenching heat treatment, and the heat treatment is performed to 1050 ℃ to 1100 ℃ to perform austenitization. The secondary heat treatment is heating to 750-800 ℃ to carry out tempering heat treatment, thereby finally obtaining the finished product of the reducing pipe.

In some embodiments, the preformed reducer is heated to 1060 ℃ to 1080 ℃ in the heat treatment. Optionally, the preformed reducer is heated to 1070 ℃.

In the embodiment, in the primary heat treatment process, the primary temperature equalizing time and the primary heat preservation time are not limited and are determined according to the wall thickness of the prefabricated reducing pipe. In some embodiments, the primary temperature equalization time is 2.5 hours to 3.5 hours and the incubation time is 3.5 hours to 4.5 hours. Optionally, the primary temperature equalizing time is 3 hours, and the heat preservation time is 4 hours.

In some embodiments, in the primary heat treatment (austenitizing), the primary cooling is not limited, and air cooling or water cooling may be used. When air cooling is adopted, the primary heat treatment is normalizing treatment. When water cooling is employed, the primary heat treatment is a quenching treatment.

In the embodiment of the present disclosure, the heating temperature is different when the secondary heat treatment, i.e., the tempering treatment, is performed according to the difference of the cooling method during the primary heat treatment.

In some embodiments, when air cooling is used for the primary cooling, the reducing pipe after the primary heat treatment is heated to 750 ℃ to 790 ℃. Optionally, heating to 770-790 ℃. Optionally, heat to 780 ℃.

In some embodiments, when water cooling is used for the primary cooling, the reducer after the primary heat treatment is heated to 780 ℃ to 820 ℃. Optionally, heating to 780-800 ℃. Optionally, heating to 790 ℃.

In the embodiment of the disclosure, the time of the secondary temperature equalization and the secondary heat preservation is not limited, and the time is determined according to the wall thickness of the prefabricated reducing pipe. In some embodiments, the secondary temperature equalization time is 2.5 hours to 3.5 hours and the secondary incubation time is 3.5 hours to 4.5 hours. Optionally, the secondary temperature equalization time is 3 hours, and the secondary heat preservation time is 4 hours.

In some embodiments, the secondary cooling is air cooled.

The embodiment of the disclosure provides a 630 ℃ ultra-supercritical unit G115 large-caliber thick-wall seamless hot-pressing reducing pipe which is manufactured by the manufacturing method.

Specific examples of the disclosed embodiments are given below, and the manufacturing method of the disclosed embodiments is described with reference to the test results. The adopted straight pipe blank is a 630 ℃ ultra supercritical unit G115 large-caliber thick-wall seamless steel pipe, the outer diameter is 570mm, and the wall thickness is 115 mm. That is, the thickness of the straight pipe blank is 20% of the outer diameter thereof.

Example 1

As shown in fig. 1 to 7, a method for manufacturing a large-caliber thick-wall seamless hot-pressing reducing pipe of a 630 ℃ ultra-supercritical unit G115 comprises the following steps:

s31, heating the straight pipe blank 10 to 1140 ℃, preserving heat for 2 hours, and then performing compression molding (for example, three-stage compression deformation) to obtain a prefabricated reducing pipe 11; wherein the outer diameter of the large-caliber end 112 of the obtained prefabricated reducing pipe 11 is 565mm, and the outer diameter of the small-caliber end 112 of the prefabricated reducing pipe 11 is 426 mm. In the press forming, a forward downward pressure is adopted, as shown in fig. 2, and the direction indicated by the arrow in the figure is the pressure direction in the press forming.

S32, heating the prefabricated reducing pipe 11 to 1060-1080 ℃, then carrying out primary temperature equalization for 3 hours, carrying out primary heat preservation for 4 hours, and then carrying out primary air cooling to room temperature to obtain a reducing pipe subjected to primary heat treatment;

s33, heating the reducing pipe subjected to the primary heat treatment to 780 ℃, then carrying out secondary temperature equalization for 3 hours, carrying out secondary heat preservation for 4 hours, and then carrying out secondary air cooling to room temperature;

and finishing the manufacture of the reducing pipe to obtain a finished product I of the reducing pipe.

Example 2

Compared with the embodiment 1, in the manufacturing method of the 630 ℃ ultra supercritical unit G115 large-caliber thick-wall seamless hot-pressing reducing pipe of the embodiment 2, the difference is that in the step S32, water cooling is adopted for primary cooling; then, in step S33, the reducing pipe after the primary heat treatment is heated to 790 ℃. The remaining steps and parameters were the same as in example 1. Thereby obtaining a finished product II of the reducing pipe.

In the embodiment of the present disclosure, in step S31 of the above embodiment, the press forming process is described with reference to fig. 2 and 3. As shown in fig. 2, the straight tube blank 10 is placed to the lower die 31 with the center thereof aligned and the axial direction of the straight tube blank 10 directed vertically upward. Then, the oil press is started to press the upper die 32 downward, so as to obtain the prefabricated reducing pipe 11. Wherein, in the pressing process, the final pressing temperature is required to be controlled to be not lower than 850 ℃ to ensure the pressing forming.

The different diameter pipes obtained in examples 1 to 2 above were subjected to a number of tests, in particular as follows:

(1) mechanical properties

The detection method comprises the following steps: the mechanical property test of the reducing pipe is carried out at multiple points by adopting an SHT4106 microcomputer to control an electro-hydraulic servo universal tester and a JBS-500B digital display semi-automatic impact tester. And (3) detecting the surface hardness of the reducing pipe by adopting an HT-1000A portable Leeb hardness tester. In the detection process, a plurality of sampling detections are carried out, and the average value of a plurality of test data is taken. The specific mechanical properties and surface hardness test results are shown in table 1.

TABLE 1

(2) Metallographic structure

Fig. 5 is a microstructure diagram of the reducing pipe i of example 1 at 500 times magnification, and fig. 6 is a grain size diagram of the reducing pipe i at 500 times magnification. Visible, metallographic structure: tempered martensite, prior austenite grain size: and 7.5 grade.

Fig. 7 is a microstructure diagram of the reducing pipe ii of example 2 at 500 times magnification, and fig. 8 is a grain size diagram of the reducing pipe i at 500 times magnification. Visible, metallographic structure: tempered martensite, prior austenite grain size: and 7.5 grade.

(3) Nondestructive testing

The pipes of examples 1 to 2 were subjected to nondestructive testing in the following manner, and the results were as follows:

carrying out ultrasonic detection according to GB/T5777-2008L2 grade, and obtaining qualified products;

carrying out magnetic powder detection according to JB/T4730.4 to obtain qualified product;

and carrying out eddy current detection according to GB/T7735-2016B grade, and obtaining the qualified product.

(4) Hydrostatic test

The pipes of examples 1 to 2 were subjected to a hydraulic test at a maximum test pressure of 20Mpa, calculated according to the test pressure formula P of 2SR/D, and the test was passed with a dwell time of 10 s.

(5) Size and appearance inspection

The 2 samples of the reducing pipes of examples 1 to 2, and the comparative samples of comparative examples 1 and 2 were individually subjected to size and appearance tests. The outside dimensions of the reducing pipe were measured with a vernier caliper, and the results were shown in table 2 below. As shown in fig. 4, the first end outer diameter is the outer diameter R of the second large-diameter end 21, and the first end wall thickness is the wall thickness M of the second large-diameter end 21; the second end outer diameter is the outer diameter r of the second small-caliber end 22, and the second end wall thickness is the wall thickness m of the second small-caliber end 22; the outside diameter of the middle section is the outside diameter D marked in fig. 4 and the wall thickness of the middle section is the wall thickness D marked in fig. 4.

TABLE 2

As can be seen from table 2, the wall thickness of the tube wall of the 2 reducing tube samples of examples 1 to 2 is uniformly transited, and the product size reaches the standard.

The surface quality of 2 reducing pipes of examples 1 to 2 was visually checked without crack, fold and scar defects.

The present application is not limited to the structures that have been described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the application is limited only by the appended claims.

Claims

The manufacturing method of the large-caliber thick-wall seamless hot-pressing reducing pipe of the ultra-supercritical unit G115 at the temperature of 1.630 ℃ is characterized by comprising the following steps of:

pressing and processing the tube blank of the straight tube to obtain a prefabricated reducing tube; the pipe blank of the straight pipe is a 630 ℃ ultra supercritical unit G115 large-caliber thick-wall seamless steel pipe;

carrying out heat treatment on the prefabricated reducing pipe to obtain a finished reducing pipe product, and finishing the manufacturing of the reducing pipe;

wherein the heat treatment comprises: heating the prefabricated reducing pipe to 1050-1100 ℃, then carrying out primary temperature equalization, carrying out primary heat preservation, and then carrying out primary cooling to room temperature to obtain the reducing pipe subjected to primary heat treatment;

and heating the reducing pipe subjected to the primary heat treatment to 750-820 ℃, then carrying out secondary temperature equalization, carrying out secondary heat preservation, and then carrying out secondary cooling to room temperature.
2. The manufacturing method according to claim 1, wherein the straight pipe blank is press-worked to obtain a prefabricated reducing pipe; the method comprises the following steps:

heating the tube blank of the straight tube, and then pressing and forming to obtain a prefabricated reducing tube; wherein the heating temperature is 1100-1200 ℃.
3. The manufacturing method according to claim 2, wherein the outer diameter of the straight pipe blank is 1 to 1.03 times the outer diameter of the large-caliber end of the prefabricated reducing pipe; the outer diameter of the large-caliber end of the prefabricated reducing pipe is 1-1.03 times of the outer diameter of the large-caliber end of the reducing pipe.
4. The manufacturing method according to claim 2, wherein the heating temperature is 1120 ℃ to 1160 ℃.
5. The manufacturing method according to any one of claims 1 to 4, wherein in the heat treatment, the preformed reducer is heated to 1060 ℃ to 1080 ℃.
6. The manufacturing method according to claim 5, wherein in the heat treatment, the primary cooling is air-cooled or water-cooled.
7. The manufacturing method according to claim 6, wherein in the heat treatment, when the primary cooling is air cooling, the reducer after the primary heat treatment is heated to 750 ℃ to 790 ℃;

and when the primary cooling adopts water cooling, heating the reducing pipe subjected to the primary heat treatment to 780-820 ℃.
8. The manufacturing method according to any one of claims 1 to 4, wherein the secondary cooling employs air cooling.
9. A production method according to any one of claims 1 to 4, wherein the wall thickness of the straight pipe blank is 20% or more of the outer diameter thereof.
10. A reducer produced by the method for producing a 630 ℃ ultra supercritical unit G115 large-caliber thick-wall seamless hot-pressed reducer according to any one of claims 1 to 9.