CN113172116A

CN113172116A - Preparation method of seamless steel pipe, seamless steel pipe and drill rod structure

Info

Publication number: CN113172116A
Application number: CN202110449270.0A
Authority: CN
Inventors: 周勇; 夏文斌; 赵勤; 彭先明; 王世明; 黄佑启
Original assignee: Hengyang Valin Steel Tube Co Ltd
Current assignee: Hengyang Valin Steel Tube Co Ltd
Priority date: 2021-04-25
Filing date: 2021-04-25
Publication date: 2021-07-27
Anticipated expiration: 2041-04-25
Also published as: CN113172116B

Abstract

The invention provides a preparation method of a seamless steel pipe, the seamless steel pipe and a drill rod structure. The preparation method of the seamless steel pipe comprises the following steps: step S10: carrying out a smelting process on the metallurgical raw material to obtain a blank; step S20: performing a punching process on the blank to obtain a capillary; step S30: rolling the hollow billet to obtain a pierced billet; step S40: carrying out sizing or reducing process on the pierced billet to obtain a hot rolled pipe; step S50: and (4) carrying out an expanding process on the hot rolled pipe to obtain the seamless steel pipe. The technical scheme of the invention can generate the non-quenched and tempered seamless steel pipe with higher yield strength.

Description

Preparation method of seamless steel pipe, seamless steel pipe and drill rod structure

Technical Field

The invention relates to the technical field of steel pipe production, in particular to a seamless steel pipe, a preparation method thereof and a drill rod structure.

Background

The rotary drilling rig is a construction mechanical device suitable for hole forming operation in building foundation engineering, is mainly suitable for soil layer construction of sandy soil, cohesive soil, silty soil and the like, and is widely applied to foundation construction of various foundations such as house buildings, cast-in-place piles, continuous walls, foundation reinforcement and the like. The rotary drilling rig is a main construction device for constructing bridge pile foundations of large buildings, railways and expressways at home and abroad due to the characteristics of high efficiency, low pollution and the like. With the increase of the investment of national infrastructure, the demand of the rotary drilling rig is increased rapidly. The drill rod structure for the rotary drilling rig is a key part of the rotary drilling rig, the drill rod structure for the rotary drilling rig is formed by nesting and combining a plurality of sections of drill rods with different outer diameters and wall thicknesses, and each section of drill rod comprises a steel pipe and an inner driving key and/or an outer driving key welded on the steel pipe. The outer diameter D of the outermost layer drill rod of the drill rod structure for the rotary drilling rig is usually over 340mm, the wall thickness S is thin, the thickness of the wall thickness S is 12-14 mm, the D/S is large and is generally more than or equal to 30, and the requirements on the strength and the toughness of the outermost layer drill rod of the drill rod structure are also high.

However, the steel pipe used in the outermost layer drill rod of the drill rod structure for the conventional rotary drilling rig generally adopts a Q345B steel-grade welded pipe with relatively low strength or a quenched and tempered steel pipe with yield strength not lower than 550MPa, wherein the welded pipe has the problem of short service life under the same stress condition due to the low yield strength of the welded pipe, and the quenched and tempered steel pipe needs a heat treatment process, so that the preparation process is relatively complex and is not easy to control, and therefore the quenched and tempered steel pipe has the problems of high manufacturing difficulty and high product reject ratio in the production process.

Therefore, it is desirable to provide a method for manufacturing a seamless steel tube, a seamless steel tube and a drill rod structure to produce a non-quenched and tempered seamless steel tube with high yield strength.

Disclosure of Invention

The invention mainly aims to provide a preparation method of a seamless steel pipe, the seamless steel pipe and a drill rod structure so as to generate a non-quenched and tempered seamless steel pipe with higher yield strength.

In order to achieve the above object, according to one aspect of the present invention, there is provided a method of manufacturing a seamless steel pipe, comprising: step S10: the method comprises the following steps of smelting a metallurgical raw material to obtain a blank, wherein the metallurgical raw material comprises Fe, C, Si, Mn, V, Nb, Al and Ni, and the metallurgical raw material comprises the following components in percentage by weight: 0.19 to 0.30% of C, 0.20 to 0.37% of Si, 1.20 to 1.70% of Mn, 0.04 to 0.12% of V, 0.03 to 0.07% of Nb, 0.02 to 0.04% of Al, and 0.3 to 1.0% of Ni; step S20: performing a punching process on the blank to obtain a capillary; step S30: rolling the hollow billet to obtain a pierced billet; step S40: carrying out sizing or reducing process on the pierced billet to obtain a hot rolled pipe; step S50: and (4) carrying out an expanding process on the hot rolled pipe to obtain the seamless steel pipe.

Further, step S20 includes: step S21: heating the blank to obtain a hot blank; step S22: and perforating the hot blank to obtain a capillary.

Further, step S21 includes: step S211: a preheating process of preheating the blank, wherein the preheating process preheats the blank to 970-990 ℃; step S212: a heating process for heating the blank subjected to the preheating process, wherein the heating process comprises a heating I section for heating the blank subjected to the preheating process to 1090-1110 ℃, a heating II section for heating the blank subjected to the heating I section to 1170-1190 ℃ and a heating III section for heating the blank subjected to the heating II section to 1240-1260 ℃; step S213: and (3) carrying out a heat-preserving soaking process on the blank subjected to the heating process, wherein the heating temperature in the soaking process is 1270-1290 ℃.

Further, the preheating time of the preheating process is 10 minutes to 14 minutes; or the heating time of the heating I section is 15 minutes to 19 minutes, the heating time of the heating II section is 25 minutes to 29 minutes, and the heating time of the heating III section is 20 minutes to 30 minutes; or the soaking process comprises a soaking I section and a soaking II section, wherein the soaking I section has the heat preservation time of 20 minutes to 24 minutes for the blank, and the soaking II section has the heat preservation time of 10 minutes to 14 minutes for the blank.

Further, in step S21, the heating time for heating the billet is 80 to 120 minutes.

Further, in step S22, the method of manufacturing a seamless steel pipe further includes the step of performing a piercing process on the hot billet at 1130 to 1150 ℃.

Further, step S40 includes: step S41: heating the pierced billet to 940-980 ℃; step S42: carrying out sizing or reducing process on the pierced billet; step S43: cooling the pierced billet at a cooling speed of 20 ℃/s to 40 ℃/s, and controlling the final cooling temperature to be 600 ℃ to 750 ℃ to obtain the hot rolled pipe.

Further, step S50 includes: step S51: heating the hot-rolled pipe at 740 ℃ to 780 ℃; step S52: expanding the hot rolled pipe; step S53: and cooling the hot rolled pipe at a cooling speed of 1.0-2.5 ℃/s to obtain the seamless steel pipe.

According to another aspect of the present invention, there is provided a seamless steel pipe produced by the above-described method of producing a seamless steel pipe.

According to another aspect of the invention, there is provided a drill rod structure comprising one or more drill rods arranged one above the other in a nested arrangement, at least one of the drill rods being made of a seamless steel tube as described above.

By applying the technical scheme of the invention, the non-quenched and tempered steel blank can be obtained through the smelting process of the metallurgical raw material in the step S10; a hollow billet can be obtained by the piercing process of the non-heat treated steel billet in step S20; through the rolling process of the hollow billet in the step S30, a hollow billet can be obtained; obtaining a hot-rolled pipe by the sizing or reducing process of the pierced billet in step S40; by the diameter expansion process of the hot-rolled pipe in step S50, a non-heat treated seamless steel pipe can be obtained. The yield strength of the seamless steel tube is relatively high, and the seamless steel tube has relatively long service life under the same stress condition because the yield strength of the seamless steel tube is relatively high; the seamless steel pipe of the non-quenched and tempered steel does not need to be subjected to a heat treatment process, and the preparation process is relatively simple and easy to control, so that the manufacturing difficulty of the seamless steel pipe of the non-quenched and tempered steel is low, and the product percent of pass is high. In conclusion, the seamless steel pipe of the non-quenched and tempered steel has the advantages of high yield strength, long service life, low manufacturing difficulty and high product percent of pass.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 shows a flow chart of an example of a method for producing a seamless steel pipe according to the present invention;

FIG. 2 shows a detailed flowchart of a manufacturing method of the seamless steel pipe of FIG. 1;

FIG. 3 shows a detailed flowchart of a manufacturing method of the seamless steel pipe of FIG. 2; and

fig. 4 shows a texture metallographic picture of a first embodiment of a seamless steel tube according to the invention.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

It is noted that, unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

In the present invention, unless specified to the contrary, use of the terms of orientation such as "upper, lower, top, bottom" or the like, generally refer to the orientation as shown in the drawings, or to the component itself in a vertical, perpendicular, or gravitational orientation; likewise, for ease of understanding and description, "inner and outer" refer to the inner and outer relative to the profile of the components themselves, but the above directional words are not intended to limit the invention.

Aiming at the problems that a welded pipe or a quenched and tempered steel pipe is generally adopted as a steel pipe used by an outermost layer drill rod of a drill rod structure for a rotary drilling rig, the welded pipe is low in yield strength, short in service life, high in manufacturing difficulty of the quenched and tempered steel pipe and high in product reject ratio, the invention provides a preparation method of a seamless steel pipe, the seamless steel pipe and the drill rod structure, and the non-quenched and tempered seamless steel pipe with high yield strength can be generated.

As shown in fig. 1, in the embodiment of the present invention, the method for manufacturing a seamless steel pipe includes:

step S10: the method comprises the following steps of smelting a metallurgical raw material to obtain a blank, wherein the metallurgical raw material comprises Fe, C, Si, Mn, V, Nb, Al and Ni, and the metallurgical raw material comprises the following components in percentage by weight: 0.19 to 0.30% of C, 0.20 to 0.37% of Si, 1.20 to 1.70% of Mn, 0.04 to 0.12% of V, 0.03 to 0.07% of Nb, 0.02 to 0.04% of Al, and 0.3 to 1.0% of Ni; step S20: performing a punching process on the blank to obtain a capillary; step S30: rolling the hollow billet to obtain a pierced billet; step S40: carrying out sizing or reducing process on the pierced billet to obtain a hot rolled pipe; step S50: and (4) carrying out an expanding process on the hot rolled pipe to obtain the seamless steel pipe.

In the above step, a non-quenched and tempered steel blank can be obtained by the smelting process of the metallurgical raw material in step S10; a hollow billet can be obtained by the piercing process of the non-heat treated steel billet in step S20; through the rolling process of the hollow billet in the step S30, a hollow billet can be obtained; obtaining a hot-rolled pipe by the sizing or reducing process of the pierced billet in step S40; by the diameter expansion process of the hot-rolled pipe in step S50, a non-heat treated seamless steel pipe can be obtained. Compared with a welded pipe, the seamless steel pipe has relatively high yield strength, and the seamless steel pipe has relatively long service life under the same stress condition because the seamless steel pipe has relatively high yield strength; compared with a quenched and tempered steel pipe, the seamless steel pipe of the non-quenched and tempered steel does not need a heat treatment process, and the preparation process is relatively simple and easy to control, so that the manufacturing difficulty of the seamless steel pipe of the non-quenched and tempered steel is low, and the product percent of pass is high. In conclusion, the seamless steel pipe of the non-quenched and tempered steel has the advantages of high yield strength, long service life, low manufacturing difficulty and high product percent of pass.

Further, the seamless steel pipe is prepared from the metallurgical raw materials, so that the formed seamless steel pipe has proper C equivalent, high yield strength and high tensile strength, can meet the application requirement of the outermost layer drill rod of the drill rod structure for the rotary drilling rig, and has the advantages of high yield and low cost in the production process.

Preferably, the metallurgical raw material includes Fe, C, Si, Mn, V, Nb, Al, Ni, and inevitable impurities. Preferably, the metallurgical raw materials comprise the following components in percentage by weight: 0.19 to 0.30% of C, 0.20 to 0.37% of Si, 1.20 to 1.70% of Mn, 0.04 to 0.12% of V, 0.03 to 0.07% of Nb, 0.02 to 0.04% of Al, and 0.3 to 1.0% of Ni, with the balance being Fe and unavoidable impurities.

C (carbon) is the most economic and basic strengthening element in steel, has obvious effect on improving the strength of the steel through the effects of solid solution strengthening and precipitation strengthening, and has the advantages of low cost and good regulation and control sensitivity. However, too much C is detrimental to the low-temperature toughness of the weld heat affected zone, so that the lower the C, the better the strength of the steel. In order to achieve both strength and toughness, the carbon content is controlled to be between 0.19% and 0.30%.

Si (silicon) is a deoxidizing element in the steel-making process, has a very important effect of reducing the content of harmful element oxygen in steel, can improve the strength, and can inhibit P from segregation in grain boundaries besides being present in the steel according to a certain proportion with Mn to inhibit Mn segregation. The silicon content is controlled between 0.20% and 0.37% for the purpose of both deoxidation, strength and inhibition of segregation.

Mn (manganese) is an austenite stabilizing element and a matrix strengthening element, and can remarkably improve the stability of austenite and promote bainite transformation, thereby remarkably improving the strength of steel and remarkably improving the toughness by combining carbon reduction. Mn can also improve the hardenability of the material, if the strength is too low, the strength can not meet the requirement, if the strength is too high, the toughness of the material is influenced, and Si and Mn exist in the steel in a certain proportion, so that the mutual segregation is favorably inhibited. Therefore, the manganese content is controlled to be between 1.20% and 1.70%.

V (vanadium) has higher precipitation strengthening effect and grain refining effect, and the yield strength and the tensile strength are improved by ferrite precipitation hardening and ferrite grain refining. When the niobium and vanadium microalloy elements are used in a composite way, the vanadium is simultaneously precipitated and strengthened in ferrite by VC (vanadium monocarbide) to improve the strength of the steel. Comprehensively, the vanadium content is controlled to be between 0.04 percent and 0.12 percent.

Nb (niobium) is an added microalloying element, and can improve the strength and simultaneously improve the low-temperature impact toughness of the steel through fine grain strengthening and precipitation strengthening. Niobium reduces the thermoplasticity of the steel and thereby increases the tendency of niobium-containing steel billets to crack. In general terms, the niobium content is controlled between 0.03% and 0.07%.

Al (aluminum) is a deoxidizer, and such an effect cannot be obtained when the content is less than 0.005%, but when the content is too high, it tends to increase inclusions, cause hairline, and lower toughness and workability, so that the aluminum content is controlled to be 0.02% to 0.04%.

Ni (nickel) is an austenite stabilizing element, is especially important for the stability of the material at low temperature, has the capacity of reducing the ductile-brittle transition temperature second to N (nitrogen) and is the best element for reducing the ductile-brittle transition temperature in metal elements, and the Ni is favorable for improving the hardenability and the strength of the material and simultaneously can improve the low-temperature plasticity of the material. Therefore, the nickel content is controlled between 0.3% and 1.0%.

In the metallurgical raw materials, the content of C is controlled to be 0.19-0.30%, so that the formed steel pipe can have certain yield strength, and meanwhile, the formed steel pipe can have better welding performance; controlling the content of Mn to be between 1.20% and 1.70%, so that Mn can better play a role in solid solution strengthening, the yield strength of the formed steel pipe is further improved, and the yield strength of the steel pipe formed by adopting the metallurgical raw material can reach 550MPa or above; in the metallurgical raw materials, a small amount of V, Nb microalloy elements play a role in controlled rolling and controlled cooling, and Al can refine grains.

In the embodiment of the invention, the C equivalent in the metallurgical raw material is controlled to be less than or equal to 0.56%. The arrangement can ensure that the obtained blank or the formed steel pipe has better strength, and simultaneously can ensure that the obtained blank or the formed steel pipe has better welding performance. The formula for calculating the Equivalent of C is CEV (Carbon Equivalent Value) ═ C + (Mn/6) + [ (Cr + Mo + V)/5] + [ (Ni + Cu)/15] (where Cr is a chromium element, Mo is a molybdenum element, and Cu is a copper element). Each letter in the above calculation formula represents the percentage (i.e. weight percentage) of the corresponding element in the above metallurgical raw material, and when the corresponding element is not included in the above metallurgical raw material, the percentage of the element is a residue (it should be noted that the metallurgical raw material includes molten iron and scrap steel, and the residue refers to the amount of the element contained in the scrap steel in a trace amount).

Preferably, the smelting process of the step S10 includes: at least one of electric furnace smelting, external refining, vacuum degassing and arc continuous casting. Preferably, in an embodiment of the present invention, the raw material is obtained by electric furnace smelting, external refining, vacuum degassing, and arc continuous casting.

Preferably, the billet may be formed by smelting the metallurgical raw material, or molten iron or molten steel obtained by smelting the metallurgical raw material. Of course, in an alternative embodiment of the present application, an existing blank after smelting can be selected as the blank in the present application to be processed according to actual conditions and actual needs, and it should be noted that the existing blank after smelting is a blank smelted from the metallurgical raw material.

As shown in fig. 2, in the embodiment of the present invention, step S20 includes: step S21: heating the blank to obtain a hot blank; step S22: and perforating the hot blank to obtain a capillary.

In the above steps, the blank is heated, and the hot blank is perforated to obtain the tubular billet, so that the uniformity of the pipe diameter of the obtained hot-rolled steel pipe (i.e., the tubular billet) and the mechanical properties of the hot-rolled steel pipe can be improved, and the subsequent treatment of the tubular billet is facilitated.

Preferably, in step S21, the billet is heated by a ring furnace.

As shown in fig. 3, in the embodiment of the present invention, step S21 includes: step S211: a preheating process of preheating the blank, wherein the preheating process preheats the blank to 970-990 ℃; step S212: a heating process for heating the blank subjected to the preheating process, wherein the heating process comprises a heating I section for heating the blank subjected to the preheating process to 1090-1110 ℃, a heating II section for heating the blank subjected to the heating I section to 1170-1190 ℃ and a heating III section for heating the blank subjected to the heating II section to 1240-1260 ℃; step S213: and (3) carrying out a heat-preserving soaking process on the blank subjected to the heating process, wherein the heating temperature in the soaking process is 1270-1290 ℃.

In the above steps, after the heating process in the preheating process, the temperature of the blank can reach 970 to 990 ℃, after the heating in the heating I section, the temperature of the blank can reach 1090 to 1110 ℃, after the heating in the heating II section, the temperature of the blank can reach 1170 to 1190 ℃, after the heating in the heating III section, the temperature of the blank can reach 1240 to 1260 ℃, and after the heating in the soaking process, the temperature of the blank can reach 1270 to 1290 ℃. The hot billet can be obtained by heating the billet. Through the sectional type heating, the blank can be heated more uniformly, the temperature of the blank is gradually increased to the soaking temperature (namely 1270-1290 ℃), heating defects (such as crack defects generated in a hot blank due to too high heating speed) are avoided, the uniformity of the wall thickness of the obtained tubular billet and the mechanical property of the tubular billet can be improved, and the subsequent treatment on the tubular billet is facilitated.

Preferably, the soaking process comprises a soaking I section and a soaking II section, which are configured to ensure that the temperature of the blank is gradually increased to the soaking temperature in the soaking process (in the embodiment of the present invention, the soaking temperature is 1270 ℃ to 1290 ℃), so as to avoid the problem that the hot blank cracks due to an excessively high temperature increase speed, and help to ensure the uniformity of the wall thickness and the mechanical properties of the hollow billet. Preferably, in the embodiment of the invention, the soaking temperatures of the soaking I section and the soaking II section are 1270-1290 ℃. It should be noted that the soaking temperatures of the soaking I section and the soaking II section may be the same or different, and the proper soaking temperature of the soaking I section and the proper soaking temperature of the soaking II section may be selected according to the actual situation and the actual needs.

Preferably, in the embodiment of the present invention, the preheating time of the preheating process is 10 minutes to 14 minutes. By the arrangement, the preheating speed of the blank can be controlled, the temperature of the blank is gradually increased to the preheating temperature (in the embodiment of the invention, the preheating temperature is 970-990 ℃), the problem that the hot blank cracks due to the excessively high heating speed is solved, the uniformity of the wall thickness of the capillary and the mechanical property of the capillary are improved, and the subsequent treatment of the capillary is facilitated.

Preferably, in the embodiment of the present invention, the heating time for the heating period I is 15 minutes to 19 minutes, the heating time for the heating period II is 25 minutes to 29 minutes, and the heating time for the heating period III is 20 minutes to 30 minutes. By the arrangement, the heating speed of the blank can be controlled, the temperature of the blank is gradually raised to the heating temperature (in the embodiment of the invention, the heating temperature is 1090-1110 ℃ of the heating section I, 1170-1190 ℃ of the heating section II and 1240-1260 ℃ of the heating section III), the problem that the hot blank cracks due to the fact that the heating speed is too high is avoided, the uniformity of the wall thickness of the tubular billet and the mechanical property of the tubular billet are improved, and the subsequent treatment of the tubular billet is facilitated.

Preferably, in the embodiment of the invention, the soaking period I of the soaking process is 20 to 24 minutes, and the soaking period II of the soaking process is 10 to 14 minutes. By the arrangement, the soaking speed of the blank can be controlled, the temperature of the blank is gradually increased to the soaking temperature (in the embodiment of the invention, the soaking temperature is 1270-1290 ℃), the problem that the hot blank cracks due to the excessively high heating speed is avoided, the uniformity of the wall thickness of the tubular billet and the mechanical property of the tubular billet are improved, and the subsequent treatment of the tubular billet is facilitated.

Preferably, in the embodiment of the present invention, in step S21, the heating time for heating the blank is 80 minutes to 120 minutes. That is, in the embodiment of the present invention, the total heating time for heating the ingot in the preheating process, the heating process (the heating I stage, the heating II stage, and the heating III stage), and the soaking process (the soaking I stage and the soaking II stage) is 80 minutes to 120 minutes. The blank is fully and uniformly heated, the problem that crystal grains of the hot blank grow up due to long-time heating can be avoided while the blank can be fully heated, heating defects (such as the defect that the hot blank generates cracks due to the fact that the temperature rising speed is too fast) can be avoided, the uniformity of the wall thickness of the obtained hollow billet and the mechanical property of the hollow billet can be improved, and subsequent processing of the hollow billet is facilitated.

Preferably, in an embodiment of the present invention, in step S22, the preparation method further includes the step of performing a piercing process on the hot blank at 1130 ℃ to 1150 ℃. And (4) perforating the hot blank obtained in the step S21 at 1130-1150 ℃ to obtain the hollow billet, thereby laying a foundation for obtaining a seamless steel pipe subsequently.

Preferably, in an embodiment of the present invention, the hot blank is perforated by using tapered rollers to obtain the hollow billet.

As shown in fig. 1 to 3, in the embodiment of the present invention, the method for manufacturing a seamless steel pipe can obtain a pierced billet by performing the rolling process on the above-mentioned pierced billet in step S30. The hollow billet can be rolled through the step S30 to obtain a pierced billet, so that the subsequent steps are facilitated.

Preferably, in an embodiment of the present invention, the hollow billet may be rolled by a continuous tube rolling mill to obtain the hollow billet.

As shown in fig. 2 and 3, in the embodiment of the present invention, step S40 includes: step S41: heating the pierced billet to 940-980 ℃; step S42: carrying out sizing or reducing process on the pierced billet; step S43: cooling the pierced billet at a cooling speed of 20 ℃/s to 40 ℃/s, and controlling the final cooling temperature to be 600 ℃ to 750 ℃ to obtain the hot rolled pipe.

Through the steps, the pierced billet can be further heated, subjected to sizing treatment and rapidly controlled and cooled after rolling, so that the hot rolled pipe is obtained. In the process, the pierced billet is reheated to raise the temperature of the pierced billet to 940-980 ℃, crystal grains can be refined in the reheating process of the pierced billet, V, Nb microalloy elements can be subjected to solid solution, a foundation can be laid for the subsequent reducing process, and the rolling and cooling control effects are improved; carrying out sizing or reducing process on the reheated pierced billet to finish sizing treatment on the pierced billet; the pierced billet subjected to sizing or reducing can be cooled according to actual needs, the purpose of controlling the final cooling temperature can be achieved by adopting the cooling speed of 20 ℃/s to 40 ℃/s and controlling the cooling time, and the final cooling temperature is finally controlled to be 600 ℃ to 750 ℃, so that the hot rolled pipe with higher strength and better toughness is obtained.

Preferably, in the embodiment of the present invention, the pierced billet is cooled on a cooling bed (preferably, in the embodiment of the present invention, the pierced billet may be selectively cooled on a small cooling bed according to actual conditions, so that resources can be saved and adaptability can be improved), and then the pierced billet is heated in a heating furnace, wherein the heating temperature of the heating furnace is 940 ℃ to 980 ℃, so that the pierced billet can be heated to 940 ℃ to 980 ℃.

Preferably, in the embodiment of the present invention, the reheated pierced billet is subjected to sizing treatment (wherein, sizing treatment may be performed by a sizing or reducing process) in step S42, the pierced billet subjected to sizing treatment is cooled at a cooling rate of 20 ℃/S to 40 ℃/S, and the final cooling temperature is controlled to be 600 ℃ to 750 ℃, so that a hot-rolled tube with high strength and good toughness can be obtained.

As shown in fig. 2 and 3, in the embodiment of the present invention, step S50 includes: step S51: heating the hot-rolled pipe at 740 ℃ to 780 ℃; step S52: expanding the hot rolled pipe; step S53: and cooling the hot rolled pipe at a cooling speed of 1.0-2.5 ℃/s to obtain the seamless steel pipe.

In the above step, the hot-rolled pipe is heated in step S51 to raise the temperature of the hot-rolled pipe to 740 to 780 ℃ to facilitate the subsequent hot-expanding process (i.e., the above diameter expansion process) of the hot-rolled pipe; expanding the diameter of the hot rolled pipe through step S52 to make the expanded diameter of the hot rolled pipe meet the requirement of the user for the diameter of the seamless steel pipe; cooling the hot-expanded pipe (i.e., the hot-rolled pipe after the diameter expansion) after the diameter expansion processing in step S53 to obtain a seamless steel pipe product; in addition, the cooling speed of the hot expanding pipe is controlled, the hot expanding pipe is cooled at the cooling speed of 1.0 ℃/s to 2.5 ℃/s to obtain the seamless steel pipe product, so that the crystal grains can be refined, V, Nb microalloy elements can better play a role in precipitation strengthening, and the shaping and the toughness of the seamless steel pipe can be improved. Through the steps, the finally obtained seamless steel tube product has high dimensional accuracy and high strength and toughness.

The invention and the embodiment of the invention also provide a seamless steel pipe, and the seamless steel pipe is prepared by the preparation method of the seamless steel pipe.

In the embodiment of the invention, the seamless steel pipe is prepared by the preparation method of the seamless steel pipe. The seamless steel pipe is a non-quenched and tempered steel seamless steel pipe with high yield strength, and has the advantages of high yield strength, long service life, low manufacturing difficulty and high product percent of pass.

It should be noted that, since the seamless steel pipe of the present application is prepared by the method for preparing a seamless steel pipe of the present application, the seamless steel pipe of the present application also has the above advantages of the method for preparing a seamless steel pipe of the present application, and details thereof are not repeated herein.

Preferably, the preparation method of the seamless steel pipe and the seamless steel pipe can be applied to the technical field of seamless steel pipe production in the metallurgical industry, the non-quenched and tempered steel seamless steel pipe with large caliber, thin wall and yield strength of 550MPa or above can be produced according to the preparation method of the seamless steel pipe, the problem of low yield strength of the steel pipe can be solved, and the produced seamless steel pipe has the advantages of high yield strength, long service life, low manufacturing difficulty, high product percent of pass, low production cost and the like, and is suitable for batch production.

The invention and the embodiment thereof also provide a drill rod structure, which comprises one or more sections of drill rods which are nested layer by layer, wherein at least one section of drill rod is made of the seamless steel pipe.

In an embodiment of the invention, the drill rod structure comprises a plurality of sections of drill rods which are nested layer by layer, and at least one section of drill rod is made of the seamless steel pipe.

In the setting, the seamless steel pipe is non-quenched and tempered steel, and the drill rod made of the seamless steel pipe has the advantages of high yield strength, long service life, low manufacturing difficulty and high leveling qualified rate.

It should be noted that, since the drill rod structure of the present application includes at least one section of drill rod made of the seamless steel tube of the present application, the drill rod structure of the present application also has the above advantages of the seamless steel tube of the present application, and details thereof are not described herein again.

Preferably, in an embodiment of the present invention, the drill rod structure further comprises an inner drive key and an outer drive key disposed on each layer of drill rods. Each drill rod is nested with other drill rods layer by layer through an inner driving key or an outer driving key arranged on the drill rod, and torque transmission among the drill rods is realized. Preferably, the inner driving key is connected with the drill rod in a welding mode. Preferably, the external driving key is connected with the drill rod in a welding mode.

Preferably, the radial sizes of the drill rods in the multiple sections of the drill rods in the layer-by-layer nested arrangement are different. Preferably, the wall thickness of the multiple sections of drill rods which are nested layer by layer can be the same, or the wall thickness of at least two sections of drill rods can be different.

Preferably, in the embodiment of the invention, the drill rod structure can be applied to a rotary drilling rig. At this moment, because the rotary drilling rig has the drilling rod structure of this application, consequently, the rotary drilling rig also has the above-mentioned advantage of the drilling rod structure of this application, and here is no longer repeated.

In the embodiment of the invention, the outer diameter of the drill rod structure for the rotary drilling rig is 406 mm-630 mm, and the wall thickness is 8 mm-15 mm.

In the embodiment of the invention, the outer diameter of the drill rod is 406mm, the wall thickness is 13mm, the specification of the drill rod is 406mm multiplied by 13mm, and the preparation process of the drill rod is as follows:

step S10: and smelting the metallurgical raw materials to obtain a blank.

Specifically, in the examples of the present invention, the above-mentioned raw material is subjected to electric furnace smelting, external refining, vacuum degassing, and arc type continuous casting to obtain the above-mentioned ingot.

Step S20: and heating the blank, and then perforating the heated blank by using a tapered roller to obtain a capillary.

Specifically, in the embodiment of the present invention, first, the blank is heated, and the heating process includes a preheating process, a heating I stage, a heating II stage, a heating III stage, a soaking I stage, and a soaking II stage. The heating time of the preheating process is 10 minutes to 14 minutes, and the temperature of the blank is increased to 970 ℃ to 990 ℃ after the heating of the preheating process; the heating time of the heating I section is 15 to 19 minutes, and the temperature of the blank is increased to 1090 to 1110 ℃ after the heating I section is heated; the heating time of the heating II section is 25 to 29 minutes, and the temperature of the blank is raised to 1170 to 1190 ℃ after the heating II section is heated; the heating time of the heating III section is 20 minutes to 30 minutes, and the temperature of the blank is increased to 1240 ℃ to 1260 ℃ after the heating of the heating III section; the heating time of the soaking I section is 20 to 24 minutes, and the temperature of the blank is increased to 1270 to 1290 ℃ after the blank is heated by the soaking I section; the heating time of the soaking II section is 10 to 14 minutes, and the temperature of the blank is increased to 1270 to 1290 ℃ after the heating of the soaking II section. And finishing heating the blank through the heating process.

Then, the heated blank is perforated at 1130 to 1150 ℃ using a conical roller to obtain the above-mentioned hollow billet.

Step S30: and rolling the hollow billet to obtain a pierced billet.

Specifically, in the embodiment of the present invention, the hollow billet is rolled by a continuous tube rolling mill to obtain the hollow billet.

Step S40: and heating, sizing, rolling and then rapidly controlling and cooling the pierced billet to obtain the hot rolled pipe.

Specifically, in the embodiment of the invention, the pierced billet is cooled on a cooling bed and then heated in a heating furnace, and the temperature of the heating furnace is controlled to be 940-980 ℃ so that the temperature of the pierced billet is increased to 940-980 ℃; sizing the heated pierced billet (sizing is completed through a sizing process or a reducing process); and cooling the pierced billet subjected to sizing treatment at a cooling speed of 20-40 ℃/s, and controlling the final cooling temperature to be 600-750 ℃ so as to obtain the hot rolled pipe with higher strength and better toughness.

Step S50: the hot rolled pipe is subjected to hot expansion (i.e., diameter expansion) to obtain a finished seamless steel pipe.

Specifically, in the embodiment of the present invention, the hot-rolled pipe is heated and subjected to hot-expanding processing, so that the radial dimension of the hot-rolled pipe subjected to hot-expanding processing can meet the user requirement, wherein the hot-rolled pipe is heated to 740 ℃ to 780 ℃ and subjected to hot-expanding processing at 740 ℃ to 780 ℃; and then, controlling and accelerating the hot expanded pipe subjected to hot expanding processing to cool at a cooling speed of 1.0-2.5 ℃/s, and finally obtaining the finished seamless steel pipe with higher dimensional accuracy and better toughness.

The specific operation process of the preparation method of the seamless steel tube of the embodiment of the invention is as follows:

smelting to obtain a blank → sawing and blanking the blank → heating the blank by an annular furnace → perforating the hot blank to obtain a tubular billet → continuously rolling the tubular billet to obtain a pierced billet → reheating the pierced billet by a stepping furnace → descaling by high pressure water → sizing the pierced billet → rapidly controlling and cooling after rolling to obtain a hot rolled tube → cooling the hot rolled tube by a cold bed → cutting the head and the tail → thermally expanding the hot rolled tube → thermally expanding → rapidly cooling after thermally expanding to obtain a seamless steel tube → performing nondestructive testing → manual inspection → word spraying → packaging and warehousing on the seamless steel tube.

The weight percentages of the metallurgical raw materials of the method for producing a seamless steel pipe according to the example of the present invention are shown in table 1. The temperature and time parameters for heating the billet in step S21 of the method for producing a seamless steel pipe according to the example of the present invention are shown in table 2. The parameters in the piercing process, the sizing or reducing process, and the expanding process of the method for producing a seamless steel pipe according to the example of the present invention are shown in table 3. The dimensional accuracy (as shown in table 4) and mechanical properties (as shown in table 5) of the seamless steel pipes produced by the methods for producing seamless steel pipes according to examples of the present invention are shown in the following tables.

TABLE 1

Examples	Fe	C	Si	Mn	V	Nb	Al	Ni
									1	Balance of	0.29	0.35	1.65	0.10	0.05	0.03	0.6
2	Balance of	0.21	0.23	1.30	0.050	0.04	0.02	0.3

The balance is the iron content obtained by subtracting the total content of the components other than iron in the metallurgical raw material from the total content of the metallurgical raw material.

TABLE 2

TABLE 3

TABLE 4

TABLE 5

As is clear from tables 4 and 5, the seamless steel pipes produced in the first example (FIG. 4 shows the metallographic structure of the seamless steel pipe of the first example) and the second example of the present invention each had an outer diameter of more than 340mm, a wall thickness of 12 to 14mm, a yield strength of 550MPa or more, and a work of impact at-20 ℃ of 50J or more. The drill rod structure made of the seamless steel pipe prepared by the first embodiment or the second embodiment of the invention has high yield strength, can better meet the requirement of high-strength drilling, and has high impact toughness so that the drill rod is not easy to form fatigue fracture.

The preparation method of the seamless steel pipe, the seamless steel pipe and the drill rod structure provided by the embodiment of the invention can realize the following technical effects:

1. in the metallurgical raw materials adopted by the method, the content of C is controlled to be 0.19-0.30%, so that the formed seamless steel pipe has certain yield strength, and meanwhile, the formed seamless steel pipe has better welding performance; controlling the content of Mn to be between 1.20% and 1.70%, so that Mn can better play a role in solid solution strengthening, further improving the yield strength of the seamless steel pipe, and the yield strength of the steel pipe formed by adopting the metallurgical raw materials can reach 550MPa or above; v and Nb of the microalloy elements can refine grains and play a role in precipitation strengthening in the controlled rolling and cooling process, so that the strength and toughness of the seamless steel pipe are further improved;

2. the preparation method of the seamless steel pipe can enable the formed seamless steel pipe to have high yield strength, good low-temperature toughness, good welding performance and good manufacturability; according to the preparation method of the seamless steel tube, a heat treatment process is not required to be carried out on the seamless steel tube in the operation process, the risk of deformation of the tube blank in the heat treatment process is favorably reduced, the ovality of the tube blank and the high-temperature damage risk of the tube blank are favorably reduced, the production process is reduced, and the production cost is reduced. The preparation method of the seamless steel pipe avoids deformation and bruise of the seamless steel pipe in the quenching process. The yield of the non-quenched and tempered steel seamless steel pipe is 5% higher than that of a quenched and tempered steel pipe;

3. the C equivalent of the seamless steel pipe prepared by the preparation method of the seamless steel pipe is less than or equal to 0.56 percent, the yield strength is more than or equal to 550Mpa, and the impact energy at minus 20 ℃ can reach more than 50J;

4. because the drilling rod structure of this application includes the drilling rod of making by the seamless steel pipe of this application, consequently for the yield strength of the drilling rod structure of this application is higher, can satisfy the demand of high strength drilling better, and impact toughness is high simultaneously makes the drilling rod be difficult for forming fatigue fracture.

From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects: through the smelting process of the metallurgical raw materials in the step S10, non-quenched and tempered steel blanks can be obtained; a hollow billet can be obtained by the piercing process of the non-heat treated steel billet in step S20; through the rolling process of the hollow billet in the step S30, a hollow billet can be obtained; obtaining a hot-rolled pipe by the sizing or reducing process of the pierced billet in step S40; by the diameter expansion process of the hot-rolled pipe in step S50, a non-heat treated seamless steel pipe can be obtained. Compared with a welded pipe, the seamless steel pipe has relatively high yield strength, and the seamless steel pipe has relatively long service life under the same stress condition because the seamless steel pipe has relatively high yield strength; compared with a quenched and tempered steel pipe, the seamless steel pipe of the non-quenched and tempered steel does not need a heat treatment process, and the preparation process is relatively simple and easy to control, so that the manufacturing difficulty of the seamless steel pipe of the non-quenched and tempered steel is low, and the product percent of pass is high. In conclusion, the seamless steel pipe of the non-quenched and tempered steel has the advantages of high yield strength, long service life, low manufacturing difficulty and high product percent of pass. Further, the seamless steel pipe is prepared from the metallurgical raw materials, so that the formed seamless steel pipe has proper C equivalent, high yield strength and high tensile strength, can meet the application requirement of the outermost layer drill rod of the drill rod structure for the rotary drilling rig, and has the advantages of high yield and low cost in the production process.

It is to be understood that the above-described embodiments are only a few, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular is intended to include the plural unless the context clearly dictates otherwise, and it should be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of features, steps, operations, devices, components, and/or combinations thereof.

It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are capable of operation in sequences other than those illustrated or described herein.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for manufacturing a seamless steel pipe, comprising:

step S10: the method comprises the following steps of carrying out a smelting process on a metallurgical raw material to obtain a blank, wherein the metallurgical raw material comprises Fe, C, Si, Mn, V, Nb, Al and Ni, and the metallurgical raw material comprises the following components in percentage by weight: 0.19 to 0.30% of C, 0.20 to 0.37% of Si, 1.20 to 1.70% of Mn, 0.04 to 0.12% of V, 0.03 to 0.07% of Nb, 0.02 to 0.04% of Al, and 0.3 to 1.0% of Ni;

step S20: carrying out a punching process on the blank to obtain a capillary;

step S30: carrying out a rolling process on the hollow billet to obtain a pierced billet;

step S40: carrying out sizing or reducing process on the pierced billet to obtain a hot rolled pipe;

step S50: and carrying out an expanding process on the hot rolled pipe to obtain the seamless steel pipe.

2. The method of manufacturing a seamless steel pipe according to claim 1, wherein the step S20 includes:

step S21: heating the blank to obtain a hot blank;

step S22: and perforating the hot blank to obtain the hollow billet.

3. The method of manufacturing a seamless steel pipe according to claim 2, wherein the step S21 includes:

step S211: a preheating process of preheating the billet, wherein the preheating process preheats the billet to 970 ℃ to 990 ℃;

step S212: a heating process of heating the billet subjected to the preheating process, the heating process including a heating I stage of heating the billet subjected to the preheating process to 1090 ℃ to 1110 ℃, a heating II stage of heating the billet subjected to the heating I stage to 1170 ℃ to 1190 ℃, and a heating III stage of heating the billet subjected to the heating II stage to 1240 ℃ to 1260 ℃;

step S213: and carrying out a heat preservation soaking process on the blank subjected to the heating process, wherein the heating temperature of the soaking process is 1270-1290 ℃.

4. The method of producing a seamless steel pipe according to claim 3,

the preheating time in the preheating process is 10 to 14 minutes; alternatively, the first and second electrodes may be,

the heating time of the heating I section is 15 minutes to 19 minutes, the heating time of the heating II section is 25 minutes to 29 minutes, and the heating time of the heating III section is 20 minutes to 30 minutes; alternatively, the first and second electrodes may be,

the soaking process comprises a soaking section I and a soaking section II, wherein the soaking section I is used for preserving the heat of the blank for 20 to 24 minutes, and the soaking section II is used for preserving the heat of the blank for 10 to 14 minutes.

5. The method of producing a seamless steel pipe according to claim 2, wherein in step S21, the heating time for heating the billet is 80 to 120 minutes.

6. The method of manufacturing a seamless steel pipe according to claim 2, further comprising a step of performing a piercing process on the hot billet at 1130 ℃ to 1150 ℃ in the step S22.

7. The method of producing a seamless steel pipe according to any one of claims 1 to 6, wherein the step S40 includes:

step S41: heating the pierced billet to 940 ℃ to 980 ℃;

step S42: carrying out a sizing or reducing process on the pierced billet;

step S43: and cooling the pierced billet at a cooling speed of 20 ℃/s-40 ℃/s, and controlling the final cooling temperature to be 600-750 ℃ to obtain the hot rolled pipe.

8. The method of producing a seamless steel pipe according to any one of claims 1 to 6, wherein the step S50 includes:

step S51: heating the hot-rolled pipe at 740 ℃ to 780 ℃;

step S52: expanding the hot rolled pipe;

step S53: and cooling the hot-rolled pipe at a cooling speed of 1.0 ℃/s-2.5 ℃/s to obtain the seamless steel pipe.

9. A seamless steel pipe, characterized in that it is produced by the method of producing a seamless steel pipe according to any one of claims 1 to 8.

10. A drill pipe structure comprising one or more lengths of drill pipe nested one within the other, at least one of the lengths of drill pipe being made from a seamless steel pipe as claimed in claim 9.