CN113172116B

CN113172116B - Preparation method of seamless steel tube, seamless steel tube and drill rod structure

Info

Publication number: CN113172116B
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: 2023-08-01
Anticipated expiration: 2041-04-25
Also published as: CN113172116A

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 tube comprises the following steps: step S10: smelting the metallurgical raw materials to obtain blanks; step S20: perforating the blank to obtain a capillary; step S30: rolling the capillary tube to obtain a pierced billet; step S40: sizing or reducing the pierced billet to obtain a hot rolled pipe; step S50: and (5) performing a diameter expansion process on the hot rolled pipe to obtain the seamless steel pipe. According to the technical scheme, the non-quenched and tempered seamless steel pipe with high yield strength can be produced.

Description

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

Technical Field

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

Background

The rotary drilling rig is construction mechanical equipment suitable for pore-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 construction, filling piles, continuous walls, foundation reinforcement and the like. The rotary drilling rig has the characteristics of high efficiency, low pollution and the like, and is currently used as main construction equipment for constructing bridge piles of large buildings, railways and expressways at home and abroad. Along with the increase of the national infrastructure investment, the demand of the rotary drilling rig is increased. The drill rod structure for the rotary drilling rig is a key component of the rotary drilling rig and 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 which are welded on the steel pipe. The outer diameter D of the outermost drill rod of the drill rod structure for the rotary drilling rig is usually more than 340mm, the wall thickness S is thinner, the thickness of the wall thickness S is between 12 and 14mm, the D/S is larger, the D/S is generally larger than or equal to 30, and the strength and toughness requirements on the outermost drill rod of the drill rod structure are higher.

However, the steel pipe used in the outermost layer of the drill rod structure for the rotary drilling rig commonly used at present 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 has the problems of high manufacturing difficulty and high reject ratio of products in the production process due to the fact that the quenched and tempered steel pipe needs to be subjected to a heat treatment procedure, and the preparation process is relatively complex and difficult to control.

Accordingly, there is a need to provide a method of producing a seamless steel pipe, and a drill pipe structure to produce a non-quenched and tempered seamless steel pipe having a 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 for manufacturing a seamless steel pipe, comprising: step S10: 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: perforating the blank to obtain a capillary; step S30: rolling the capillary tube to obtain a pierced billet; step S40: sizing or reducing the pierced billet to obtain a hot rolled pipe; step S50: and (5) performing a diameter expansion 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 blank is preheated to 970-990 ℃ in the preheating process; step S212: a heating process of heating the blank subjected to the preheating process, the heating process including a heating section I of heating the blank subjected to the preheating process to 1090 ℃ to 1110 ℃, a heating section II of heating the blank subjected to the heating section I to 1170 ℃ to 1190 ℃, and a heating section III of heating the blank subjected to the heating section II to 1240 ℃ to 1260 ℃; step S213: and (3) a soaking process of preserving heat of the blank subjected to the heating process, wherein the heating temperature of 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 section I is 15 to 19 minutes, the heating time of the heating section II is 25 to 29 minutes, and the heating time of the heating section III is 20 to 30 minutes; or the soaking process comprises a soaking section I and a soaking section II, wherein the soaking section I has the heat preservation time of 20 minutes to 24 minutes for the blank, and the soaking section II has the heat preservation time of 10 minutes to 14 minutes for the blank.

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

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

Further, step S40 includes: step S41: heating the pierced billet to 940-980 ℃; step S42: sizing or reducing the pierced billet; step S43: and (3) cooling the pierced billet at a cooling rate of 20 ℃/s to 40 ℃/s, and controlling the final cooling temperature to 600 ℃ to 750 ℃ to obtain the hot rolled pipe.

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

According to another aspect of the present invention, there is provided a seamless steel pipe prepared by the above-mentioned method for preparing a seamless steel pipe.

According to another aspect of the invention, there is provided a drill rod structure comprising one or more sections of drill rod nested one within the other, at least one section of drill rod 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 materials in the step S10; through the perforating process of the non-quenched and tempered steel blank in the step S20, a blank pipe can be obtained; the pierced billet can be obtained through the rolling process of the hollow billet in the step S30; the hot rolled pipe can be obtained through the sizing or reducing process of the pierced billet in the step S40; by the diameter expansion process of the hot rolled pipe in step S50, a non-quenched and tempered seamless steel pipe can be obtained. The yield strength of the seamless steel pipe is relatively high, and the service life of the seamless steel pipe is relatively long under the condition of the same stress because the yield strength of the seamless steel pipe is relatively high; the non-quenched and tempered steel seamless steel pipe does not need a heat treatment process, and the preparation flow is relatively simple and easy to control, so that the non-quenched and tempered steel seamless steel pipe is low in manufacturing difficulty and high in product qualification rate. In summary, the seamless steel tube of the non-quenched and tempered steel has the advantages of higher yield strength, longer service life, lower manufacturing difficulty and higher product qualification rate.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:

fig. 1 shows a flowchart of an embodiment of a method of manufacturing a seamless steel pipe according to the present invention;

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

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

fig. 4 shows a structure golden phase diagram of a first embodiment of a seamless steel pipe according to the present invention.

Detailed Description

It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The invention will be described in detail below with reference to the drawings in connection with embodiments.

It is noted that 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 unless otherwise indicated.

In the present invention, unless otherwise indicated, terms of orientation such as "upper, lower, top, bottom" are used generally with respect to the orientation shown in the drawings or with respect to the component itself in the vertical, upright or gravitational direction; also, for ease of understanding and description, "inner and outer" refers to inner and outer relative to the profile of each component itself, but the above-mentioned orientation terms are not intended to limit the present invention.

Aiming at the problems that the welded pipe or the quenched and tempered steel pipe is generally adopted as the steel pipe used by the outermost layer of the drill pipe structure for the rotary drilling rig at present, the welded pipe has lower yield strength, short service life and higher product reject ratio, the invention and the embodiment of the invention provide a preparation method of a seamless steel pipe, the seamless steel pipe and the drill pipe structure, and the non-quenched and tempered seamless steel pipe with higher yield strength can be generated.

As shown in fig. 1, in the embodiment of the invention, the preparation method of the seamless steel pipe comprises the following steps:

step S10: 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: perforating the blank to obtain a capillary; step S30: rolling the capillary tube to obtain a pierced billet; step S40: sizing or reducing the pierced billet to obtain a hot rolled pipe; step S50: and (5) performing a diameter expansion 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 the step S10; through the perforating process of the non-quenched and tempered steel blank in the step S20, a blank pipe can be obtained; the pierced billet can be obtained through the rolling process of the hollow billet in the step S30; the hot rolled pipe can be obtained through the sizing or reducing process of the pierced billet in the step S40; by the diameter expansion process of the hot rolled pipe in step S50, a non-quenched and tempered seamless steel pipe can be obtained. The yield strength of the seamless steel pipe is relatively higher than that of a welded pipe, and the service life of the seamless steel pipe is relatively longer under the condition of being stressed in the same way because the yield strength of the seamless steel pipe is relatively higher; compared with the quenched and tempered steel pipe, 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 flow 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 yield is high. In summary, the seamless steel tube of the non-quenched and tempered steel has the advantages of higher yield strength, longer service life, lower manufacturing difficulty and higher product qualification rate.

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

Preferably, the metallurgical raw material comprises Fe, C, si, mn, V, nb, al, ni and unavoidable 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, the balance being Fe and unavoidable impurities.

C (carbon) is the most economical 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 sensitivity. However, too much C is detrimental to the low temperature toughness of the weld heat affected zone, so the lower C should be, the better while ensuring 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 percent.

Si (silicon) is a deoxidizing element in the steelmaking process, plays a very important role in reducing the content of harmful element oxygen in steel, can improve the strength, and can inhibit the segregation of Mn in the steel and P in the grain boundary besides being present in a certain proportion with Mn. In order to achieve both deoxidation, strength and inhibition of segregation, the silicon content is controlled between 0.20% and 0.37%.

Mn (manganese) is an austenite stabilizing element and is also a matrix strengthening element, mn can obviously improve the stability of austenite and promote bainite transformation, so that the strength of steel is obviously improved, and the toughness can be obviously improved by combining carbon reduction. Mn can also improve the hardenability of the material, if too low, the strength can not meet the requirement, and if too high, the toughness of the material is affected, and Si and Mn exist in the steel in a certain proportion, thereby being beneficial to inhibiting the segregation of Si and Mn. Thus, the manganese content is controlled between 1.20% and 1.70%.

V (vanadium) has higher precipitation strengthening effect and grain refining effect, and the yield and tensile strength are improved by ferrite precipitation hardening and refining ferrite grains. When the niobium and vanadium microalloy elements are compositely used, vanadium is simultaneously precipitated and strengthened by VC (vanadium carbide) in ferrite to improve the strength of the steel. The vanadium content is controlled to be between 0.04% and 0.12% by comprehensive consideration.

Nb (niobium) is an added microalloying element, and can improve strength by fine grain strengthening and precipitation strengthening, and can improve low temperature impact toughness of steel. Niobium reduces the heat plasticity of the steel and thereby increases the hot tearing tendency of the niobium-containing steel billets. The niobium content is controlled to be between 0.03% and 0.07% by comprehensive consideration.

Al (aluminum) is a deoxidizer, and when the content is too high, it is liable to cause increase of inclusions, hairline generation, and reduction of toughness and workability, and therefore, the aluminum content is controlled to be 0.02% to 0.04%, although such effect cannot be attained when the content is less than 0.005%.

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

In the metallurgical raw materials, the content of C is controlled to be between 0.19 and 0.30 percent, so that the formed steel pipe can be ensured to have certain yield strength, and meanwhile, the formed steel pipe can be ensured to have better welding performance; the content of Mn is controlled between 1.20% and 1.70%, so that Mn can better play a solid solution strengthening role, thereby further improving the yield strength of the formed steel pipe, and the yield strength of the steel pipe formed by adopting the metallurgical raw material can reach 550MPa or more; in the metallurgical raw materials, a small amount of V, nb microalloy elements play a role in controlling rolling and 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 percent. The arrangement can ensure that the obtained blank or the formed steel pipe has better strength, and simultaneously ensure that the obtained blank or the formed steel pipe has better welding performance. The calculation formula of the C equivalent is CEV (Carbon Equivalent Value ) =C+ (Mn/6) + [ (Cr+Mo+V)/5 ] + [ (Ni+Cu)/15 ] (wherein Cr is chromium element, mo is molybdenum element, and Cu is copper element). Wherein each letter in the above calculation formula represents the percentage content (i.e., weight percent) 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 content of the element is a residue (it should be noted that the metallurgical raw material includes molten iron and scrap, and the residue herein refers to the amount of the trace element contained in the scrap).

Preferably, the smelting process of the step S10 includes: at least one of the processes of electric furnace smelting, external refining, vacuum degassing, arc continuous casting and the like. Preferably, in the embodiment of the present invention, the above metallurgical raw material is subjected to electric furnace smelting, external refining, vacuum degassing and arc continuous casting to obtain the above ingot.

Preferably, the ingot may be smelted from the metallurgical raw material or molten iron or molten steel smelted from the metallurgical raw material. Of course, in an alternative embodiment of the present application, a ready-made billet after smelting may be selected as a billet in the present application according to actual situations and actual needs, and it should be noted that the ready-made billet after smelting is a billet 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 steps, the blank is heated, and the hot blank is perforated to obtain the blank pipe, so that the uniformity of the pipe diameter of the obtained hot rolled steel pipe (namely the blank pipe) and the mechanical property of the hot rolled steel pipe can be improved, and the subsequent treatment of the blank pipe is facilitated.

Preferably, in the step S21, the blank 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 blank is preheated to 970-990 ℃ in the preheating process; step S212: a heating process of heating the blank subjected to the preheating process, the heating process including a heating section I of heating the blank subjected to the preheating process to 1090 ℃ to 1110 ℃, a heating section II of heating the blank subjected to the heating section I to 1170 ℃ to 1190 ℃, and a heating section III of heating the blank subjected to the heating section II to 1240 ℃ to 1260 ℃; step S213: and (3) a soaking process of preserving heat of the blank subjected to the heating process, wherein the heating temperature of the soaking process is 1270-1290 ℃.

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

Preferably, the soaking process comprises a soaking section I and a soaking section II, so that the temperature of the blank is gradually increased to a soaking temperature (the soaking temperature is 1270 ℃ to 1290 ℃ in the embodiment of the invention) in the soaking process, the problem that the hot blank cracks due to the excessively high heating speed is avoided, and the uniformity of the wall thickness and the mechanical property of the blank tube are ensured. Preferably, in the embodiment of the present invention, the soaking temperature of the soaking section I and the soaking section II is 1270 ℃ to 1290 ℃. The soaking temperatures of the soaking section I and the soaking section II may be the same or different, and appropriate soaking temperatures of the soaking section I and the soaking section II may be selected according to actual conditions and actual needs.

Preferably, in an 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, so that 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 is cracked due to the fact that the heating speed is too high is avoided, uniformity of wall thickness of the capillary tube and mechanical property of the capillary tube are improved, and subsequent treatment of the capillary tube is facilitated.

Preferably, in the embodiment of the present invention, the heating time of the heating section I is 15 minutes to 19 minutes, the heating time of the heating section II is 25 minutes to 29 minutes, and the heating time of the heating section III is 20 minutes to 30 minutes. By the arrangement, the heating speed of the blank can be controlled, so that the temperature of the blank is gradually increased to the heating temperature (in the embodiment of the invention, the heating temperature is 1090-1110 ℃ in the heating section I, 1170-1190 ℃ in the heating section II and 1240-1260 ℃ in the heating section III), the problem that cracks are generated on the hot blank due to the fact that the heating speed is too high is avoided, uniformity of wall thickness of the capillary tube and mechanical property of the capillary tube are improved, and subsequent treatment on the capillary tube 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, so that 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 is cracked due to the fact that the heating speed is too high is avoided, uniformity of wall thickness of the capillary tube and mechanical property of the capillary tube are improved, and subsequent treatment of the capillary tube 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 blank material by the preheating process, the heating process (heating section I, heating section II, and heating section III), and the soaking process (soaking section I and soaking section II) is 80 minutes to 120 minutes. The setting like this can guarantee to heat fully and evenly the blank, can avoid the problem that the grain of the hot base grows up because heating for a long time when guaranteeing that the blank can fully heat, can avoid appearing heating defect (for example because the heating rate is too fast causes the hot base to produce crack defect), can promote the homogeneity of the wall thickness of the blank tube that obtains and the mechanical properties of blank tube, make things convenient for the follow-up processing to above-mentioned blank tube.

Preferably, in the embodiment of the present invention, in step S22, the manufacturing method further includes a step of performing a piercing process on the hot blank at 1130 ℃ to 1150 ℃. And (3) perforating the hot blank obtained in the step S21 at 1130-1150 ℃ to obtain the blank pipe, and laying a foundation for obtaining a seamless steel pipe later.

Preferably, in an embodiment of the present invention, the hot blank is perforated by a conical roller to obtain the capillary.

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

Preferably, in the embodiment of the present invention, the above-mentioned raw pipe may be rolled by a continuous pipe mill to obtain the above-mentioned raw pipe.

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: sizing or reducing the pierced billet; step S43: and (3) cooling the pierced billet at a cooling rate of 20 ℃/s to 40 ℃/s, and controlling the final cooling temperature to 600 ℃ to 750 ℃ to obtain the hot rolled pipe.

Through the steps, the pierced billet can be further heated, sized and cooled by rapid control after rolling, so that the hot rolled pipe is obtained. In the process, the pierced billet is reheated to enable the temperature of the pierced billet to be increased to 940-980 ℃, grains can be refined in the reheating process of the pierced billet, V, nb microalloy elements are enabled to be solid-solution, meanwhile, a foundation can be laid for the subsequent reducing process, and the rolling and cooling control effects are improved; sizing or reducing the reheated pierced billet to finish sizing treatment of the pierced billet; the pierced billet subjected to sizing or reducing process can be cooled according to actual needs, the cooling speed of 20 ℃/s to 40 ℃/s is adopted, the aim of controlling the final cooling temperature can be achieved by controlling the cooling time, and finally the final cooling temperature is 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 practical situations, so as to save resources and improve adaptability), and then the pierced billet is heated in a heating furnace at a heating temperature of 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 blank is sized (wherein the sizing process may be performed by sizing or reducing process) through the step S42, the sized pierced blank is cooled at a cooling rate of 20 ℃/S to 40 ℃/S, and a final cooling temperature is controlled to 600 ℃ to 750 ℃, so that a hot rolled tube having high strength and high 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 tube at 740 ℃ to 780 ℃; step S52: expanding the hot rolled pipe; step S53: and cooling the hot rolled pipe at a cooling rate of 1.0 ℃/s to 2.5 ℃/s to obtain a seamless steel pipe.

In the above steps, the hot rolled tube is heated in step S51 to raise the temperature of the hot rolled tube to 740 ℃ to 780 ℃, so that the hot rolled tube is conveniently subjected to subsequent hot expansion (i.e., the above expanding process); performing expanding processing on the hot rolled pipe through the step S52, so that the pipe diameter of the hot rolled pipe after expanding meets the pipe diameter requirement of a user on the seamless steel pipe; cooling the heat expanded pipe subjected to the expanding processing (namely, the hot rolled pipe subjected to the expanding processing) through a step S53, so as to obtain a seamless steel pipe product; in addition, the cooling speed of the thermal expansion pipe is controlled, the thermal expansion pipe is cooled at the cooling speed of 1.0 ℃/s to 2.5 ℃/s to obtain the seamless steel pipe product, so that crystal grains can be refined, the V, nb micro-alloy element can better play a role of precipitation strengthening, and the shaping and toughness of the seamless steel pipe can be improved. Through the steps, the finally obtained seamless steel tube product has higher dimensional accuracy and better strength and toughness.

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

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 higher yield strength, and has the advantages of higher yield strength, longer service life, lower manufacturing difficulty and higher product qualification rate.

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 will not be described in detail here.

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

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

In the 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 arrangement, the seamless steel pipe is a non-quenched and tempered steel seamless steel pipe, and the drill rod manufactured by the seamless steel pipe has the advantages of higher yield strength, longer service life, lower manufacturing difficulty and higher leveling qualification 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 pipe of the present application, the drill rod structure of the present application also has the above advantages of the seamless steel pipe of the present application, and will not be described herein.

Preferably, in an embodiment of the present invention, the drill rod structure further comprises an inner drive key and an outer drive key provided 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, so that torque transmission among the drill rods is realized. Preferably, the inner drive key is welded to the drill rod. Preferably, the external drive key is welded to the drill rod.

Preferably, the radial sizes of the drill rods which are arranged in a multi-section layer-by-layer nested mode are different. Preferably, the wall thickness of the drill rods which are arranged in a multi-section layer-by-layer nested manner can be the same, and the wall thickness of at least two sections of drill rods can also be different.

Preferably, in an embodiment of the present invention, the drill rod structure may be applied to a rotary drilling rig. At this time, since the rotary drilling rig has the drill rod structure of the present application, the rotary drilling rig also has the above advantages of the drill rod structure of the present application, and will not be described here again.

In an embodiment of the invention, the outer diameter of the drill rod structure for the rotary drilling rig is between 406mm and 630mm, and the wall thickness is between 8mm and 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: smelting the metallurgical raw materials to obtain a blank.

Specifically, in the embodiment of the invention, the metallurgical raw material is subjected to electric furnace smelting, external refining, vacuum degassing and arc continuous casting to obtain the blank.

Step S20: heating the blank, and then perforating the heated blank by adopting a conical roller to obtain a blank pipe.

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

Then, the heated blank is perforated by a conical roller at 1130 ℃ to 1150 ℃ to obtain the capillary.

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

Specifically, in the embodiment of the invention, the pipe rolling is performed on the blank pipe by using a continuous pipe mill to obtain the pierced blank.

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

Specifically, in the embodiment of the invention, the pierced billet is heated in a heating furnace after being cooled on a cooling bed, and the temperature of the heating furnace is controlled to be 940-980 ℃ so that the temperature of the pierced billet is increased to be 940-980 ℃; sizing the heated pierced billet (sizing is finished through sizing process or reducing process); and cooling the pierced billet after sizing at a cooling rate of 20-40 ℃ per second, and controlling the final cooling temperature at 600-750 ℃ to obtain the hot rolled pipe with higher strength and better toughness.

Step S50: and performing hot expansion processing (namely, diameter expansion processing) on the hot rolled pipe to obtain a finished seamless steel pipe.

Specifically, in the embodiment of the invention, the hot rolled pipe is heated and subjected to hot expansion processing, so that the radial dimension of the hot rolled pipe after the hot expansion processing can meet the requirement of a user, wherein the temperature of the hot rolled pipe is increased to 740-780 ℃ by heating the hot rolled pipe, and the hot rolled pipe is subjected to hot expansion processing at 740-780 ℃; and then, performing controlled accelerated cooling on the thermal expansion pipe subjected to the thermal expansion processing, wherein the cooling speed is 1.0 ℃/s to 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 pipe in the embodiment of the invention is as follows:

smelting to obtain a blank, sawing the blank, heating the blank by a ring furnace, perforating the hot blank to obtain a blank pipe, rolling the blank pipe continuously to obtain a blank pipe, reheating the blank pipe by a step furnace, descaling by high-pressure water, sizing the blank pipe, cooling by rapid control after rolling to obtain a hot rolled pipe, cooling the hot rolled pipe by a cooling bed, cutting the head and the tail, heating the hot rolled pipe by hot expansion, heating to obtain a seamless steel pipe by rapid cooling after hot expansion, performing nondestructive inspection on the seamless steel pipe, manually inspecting, spraying characters, packaging and warehousing.

The weight percentages of the components of the metallurgical raw materials of the preparation method of the seamless steel pipe according to the embodiment of the 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 embodiment of the present invention are shown in table 2. Parameters in the piercing process, sizing or reducing process, and expanding process of the method for manufacturing a seamless steel pipe according to the embodiment 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 prepared by the preparation method of the seamless steel pipes according to the examples of the present invention are shown in the following table.

TABLE 1

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

The balance is the total content of the metallurgical raw material minus the total content of the components other than iron in the metallurgical raw material.

TABLE 2

TABLE 3 Table 3

TABLE 4 Table 4

TABLE 5

From tables 4 and 5, it is understood that the outer diameters of the seamless steel pipes prepared in the first example (fig. 4 shows the structure golden phase diagram of the seamless steel pipes of the first example) and the second example of the present invention are both larger than 340mm, the wall thicknesses are both between 12 and 14mm, the yield strengths are both above 550MPa, and the impact powers at-20 ℃ are both above 50J. The drill rod structure made of the seamless steel pipe prepared by the first embodiment or the second embodiment of the invention has higher 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 of 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 between 0.19 and 0.30 percent, so that the formed seamless steel tube can be ensured to have certain yield strength, and meanwhile, the formed seamless steel tube can be ensured to have better welding performance; the content of Mn is controlled between 1.20% and 1.70%, so that Mn can better play a solid solution strengthening role, thereby further improving the yield strength of the seamless steel tube, and the yield strength of the steel tube formed by adopting the metallurgical raw materials can reach 550MPa or more; the V and Nb of the microalloy elements can refine grains and play a role in precipitation strengthening in the process of rolling and cooling control, so that the strength and toughness of the seamless steel tube are further improved;

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

3. the C equivalent of the seamless steel tube prepared by the preparation method of the seamless steel tube is less than or equal to 0.56%, 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 drill rod structure of this application includes the drill rod of being made by the seamless steel pipe of this application, consequently for the yield strength of the drill rod structure of this application is higher, can satisfy the demand of high strength drilling better, and impact toughness is high simultaneously and makes the drill rod be difficult for forming fatigue fracture.

From the above description, it can be seen that the above 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; through the perforating process of the non-quenched and tempered steel blank in the step S20, a blank pipe can be obtained; the pierced billet can be obtained through the rolling process of the hollow billet in the step S30; the hot rolled pipe can be obtained through the sizing or reducing process of the pierced billet in the step S40; by the diameter expansion process of the hot rolled pipe in step S50, a non-quenched and tempered seamless steel pipe can be obtained. The yield strength of the seamless steel pipe is relatively higher than that of a welded pipe, and the service life of the seamless steel pipe is relatively longer under the condition of being stressed in the same way because the yield strength of the seamless steel pipe is relatively higher; compared with the quenched and tempered steel pipe, 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 flow 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 yield is high. In summary, the seamless steel tube of the non-quenched and tempered steel has the advantages of higher yield strength, longer service life, lower manufacturing difficulty and higher product qualification rate. Further, the seamless steel tube is prepared from the metallurgical raw materials, so that the formed seamless steel tube has the advantages of proper C equivalent, higher yield strength and better tensile strength, can meet the application requirements of the outermost layer drill rod of the drill rod structure for the rotary drilling rig, and has higher yield and lower cost in the production process.

It will be apparent that the embodiments described above are merely some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the 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 in accordance with the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated 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 the present application and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that embodiments of the present application described herein may be implemented in sequences other than those illustrated or described herein.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The preparation method of the seamless steel tube is characterized by comprising the following steps:

step S10: 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: perforating the blank to obtain a capillary;

step S30: rolling the capillary tube to obtain a pierced billet;

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

step S50: performing a diameter expansion process on the hot rolled pipe to obtain a seamless steel pipe;

the step S40 includes:

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

step S42: sizing or reducing the pierced billet;

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

the step S50 includes:

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

step S52: expanding the hot rolled pipe;

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

2. The method for producing a seamless steel pipe according to claim 1, wherein the step S20 comprises:

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

step S22: and perforating the hot blank to obtain the capillary.

3. The method for producing a seamless steel pipe according to claim 2, wherein the step S21 comprises:

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

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

step S213: and a soaking process of maintaining the temperature of the blank subjected to the heating process, wherein the heating temperature of the soaking process is 1270-1290 ℃.

4. A method for producing a seamless steel pipe according to claim 3, wherein,

the preheating time of the preheating process is 10 minutes to 14 minutes; or alternatively, the process may be performed,

the heating time of the heating section I is 15 to 19 minutes, the heating time of the heating section II is 25 to 29 minutes, and the heating time of the heating section III is 20 to 30 minutes; or alternatively, the process may be performed,

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

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

6. A method of producing a seamless steel pipe according to claim 2, further comprising the step of perforating the hot blank at 1130 ℃ to 1150 ℃ in step S22.

7. A seamless steel pipe, characterized in that the seamless steel pipe is produced by the production method of the seamless steel pipe according to any one of claims 1 to 6.

8. A drill rod structure, characterized in that the drill rod structure comprises one or more sections of drill rods nested layer by layer, at least one section of drill rods being made of the seamless steel pipe according to claim 7.