CN112893470B - Seamless steel tube forming process - Google Patents
Seamless steel tube forming process Download PDFInfo
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- CN112893470B CN112893470B CN202110073289.XA CN202110073289A CN112893470B CN 112893470 B CN112893470 B CN 112893470B CN 202110073289 A CN202110073289 A CN 202110073289A CN 112893470 B CN112893470 B CN 112893470B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B23/00—Tube-rolling not restricted to methods provided for in only one of groups B21B17/00, B21B19/00, B21B21/00, e.g. combined processes planetary tube rolling, auxiliary arrangements, e.g. lubricating, special tube blanks, continuous casting combined with tube rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/32—Soft annealing, e.g. spheroidising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
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- Heat Treatment Of Steel (AREA)
Abstract
A technology for forming seamless steel tube includes such steps as drilling central hole on round steel rod axially to obtain product A, heating to 100 deg.C within liquidus temp range at speed less than 6 deg.C/min, holding temp to obtain product B, extruding the Mo top through the central hole of product B by perforating machine to make product B become longer and become bigger in diameter, making the guide plate of perforating machine to guide product B to become longer in fixed direction, putting round rod-shaped internal mould in product D and product C, hot rolling by hot rolling machine and external mould to make product D become shorter and longer, naturally cooling product D, holding product D at 240-300 deg.C, taking out internal mould, annealing and spheroidizing. The invention has the advantage of forming the high-hardness material into the seamless steel pipe, and is particularly suitable for forming Cr12MoV into the seamless steel pipe.
Description
Technical Field
The invention belongs to the field of seamless steel tube forming technology.
Background
The existing seamless steel tube forming process comprises an extrusion method process and a cold drawing method process. The extrusion method process is that a puncher is used for punching round steel, and then an extruder is used for extruding the punched round steel into a seamless steel pipe; the cold drawing process is to draw the steel pipe blank through a pipe drawing die to make the steel pipe become thin and elongate gradually to form a seamless steel pipe. The extrusion method process and the cold-drawing method process have high requirements on raw materials, and the soft materials are required to ensure that the ductility of the materials is good, so that the raw materials can be smoothly extended into the seamless steel pipe, the obtained seamless steel pipe has low hardness and cannot be applied to occasions with high requirements on the hardness of the steel pipe, particularly Cr12MoV with high hardness and poor ductility, and the seamless steel pipe cannot be formed by the extrusion method process and the cold-drawing method process. Therefore, the existing seamless steel pipe forming process has the defect that a high-hardness material cannot be formed into a seamless steel pipe, and particularly, cr12MoV cannot be formed into the seamless steel pipe.
Disclosure of Invention
The invention aims to provide a seamless steel tube forming process. The invention has the advantage of forming the high-hardness material into the seamless steel pipe, and is particularly suitable for forming Cr12MoV into the seamless steel pipe.
The technical scheme of the invention is as follows: a seamless steel tube forming process comprises the following steps,
a. making central hole on the round steel to obtain product A,
b. heating the product A to the liquidus temperature within 100 deg.C at a heating speed of less than 6 deg.C/min, maintaining the temperature to obtain product B,
c. extruding the molybdenum plug through the center hole of the B product by using a puncher, lengthening the length of the B product, increasing the diameter of the center hole, rotating at 50-70r/min, guiding the B product by a guide plate of the puncher, lengthening the B product in a fixed direction to obtain a C product,
d. putting round rod-shaped inner mold into product C to obtain product D,
e. continuously hot rolling the outer peripheral surface of the product D by using a hot rolling mill and an external mold to reduce the outer diameter and lengthen the length of the product D, naturally cooling the product D to 240-300 ℃ during hot rolling to obtain a product E, extracting the internal mold in the product E to obtain a product F,
g. and performing spheroidizing annealing on the F product to obtain a finished product.
In the seamless steel tube forming process, in the step a, the round steel has the diameter of 150-190mm, the length of 1.8-3m, the hardness of 207-255HBW, and the diameter of the central hole is 45-55mm.
In the seamless steel tube forming process, the diameter of the round steel is 170mm, and the diameter of the central hole is 50mm.
In the seamless steel pipe forming process, in the step a, the round steel is made of Cr12MoV, and in the step b, the product A is heated to 1180-1220 ℃.
In the seamless steel tube forming process, in the step c, the rotating speed of the plug is 60r/min.
In the seamless steel tube forming process, in the step c, the roller of the piercer is directionally cooled at regular time.
In the seamless steel pipe forming process, the rollers of the hot rolling mill are cooled in a timed and directional manner.
Compared with the prior art, the blank with the central hole is heated at a lower temperature rise speed, so that the difference between the internal temperature and the external temperature of the blank is smaller, the difference between the internal temperature and the external temperature of the blank in the heating process is reduced, the surface crack of the blank is not easy to generate in the heating process, and the possibility of the blank cracking in the subsequent processing process is reduced. The blank is heated to the temperature near the liquidus temperature, so that the blank is in a semi-solid state, is soft and has good ductility, and is subjected to heat preservation, so that the solid phase structure of the alloy of the blank is converted from dendrite to granular crystal grains through a rosette shape, and the obtained fine, uniform and round granular non-dendrite structure further improves the ductility of the blank and retains certain strength, thereby facilitating subsequent perforation and hot rolling. Through the improvement, the blank made of harder materials can also be formed into the seamless steel pipe. Therefore, the invention has the advantage of forming the high-hardness material into the seamless steel pipe, and is particularly suitable for forming Cr12MoV into the seamless steel pipe.
Detailed Description
The present invention is further illustrated by the following examples, which are not to be construed as limiting the invention.
Example 1. A seamless steel tube forming process comprises the following steps,
a. making a central hole with diameter of 50mm on the round steel in the axial direction, making the round steel material Cr12MoV (liquidus temperature 1270 ℃), external diameter 170mm, length 2m, hardness 230HBW, obtaining A product,
b. slowly heating the product A to 1200 ℃ by using a circular furnace or a linear furnace, raising the heating temperature at a speed of 5 ℃/min, and preserving heat for 40min to obtain a product B, wherein the slow heating aims at avoiding surface cracks caused by the difference between the internal temperature and the external temperature of the product B, the heat preservation aims at enabling the internal temperature and the external temperature of the product B to be consistent and changing the metallographic structure, and the obtained fine, uniform and round granular non-dendritic crystal structures have good ductility, so that the product B has good ductility, is convenient for subsequent perforation and hot rolling, and retains certain strength, and cannot cause poor forming in the subsequent perforation and hot rolling processes,
c. extruding the molybdenum top head through a center hole of the B product by using a puncher, wherein the rotating speed of the molybdenum top head is 60r/min, the punching speed is 0.73m/min, and the length of the B product is lengthened, and the diameter of the center hole is enlarged; a guide plate of the puncher guides the B product to be lengthened towards a fixed direction; the heat generated by the friction between the product B and the molybdenum top is basically close to the heat dissipated by the natural cooling of the product B, so that the temperature of the product B is ensured to be relatively constant in the perforation process, and the product B is prevented from cracking and damaging due to temperature reduction; and (3) in the process of punching, cooling water is not introduced into the roller of the puncher, and after the punching is finished, the roller is cooled by introducing water to protect the roller, wherein the water flowing direction is the roller direction, so that the product C is obtained.
d. Putting a round rod-shaped inner mold into the product C, wherein the length of the inner mold exceeds the length of the product C, the diameter of the inner mold is equal to the inner diameter of a finished product, and obtaining a product D,
e. continuously hot rolling the outer peripheral surface of the D product by using a hot rolling mill and an external mold to reduce the outer diameter and lengthen the length of the D product; when in hot rolling, the product D is naturally cooled to 280 ℃; when in hot rolling, the roller of the hot rolling mill is not filled with water, and after the perforation is finished, the roller is filled with cooling water to protect the roller, wherein the water filling direction is the roller direction; to obtain the product E, namely the product E,
f. extracting the inner mold of the product E, keeping the temperature of the product E at 280 ℃ to obtain a product F,
g. and (3) rapidly feeding the F product into a heat treatment furnace for spheroidizing annealing, cutting off two ends (the end has larger deformation and needs to be cut off) of the annealed F product, and cutting off the total length by 20-30cm to obtain a finished product, wherein the hardness of the finished product is 245HBW. The spheroidizing annealing aims at eliminating stress and preventing cracking.
The finished product can be further heat treated until the hardness is more than or equal to 68HRC.
The 500 finished products of the example 1 were inspected, the number of the finished products with surface cracks was zero, and then ultrasonic flaw detection was performed, and 1 finished product had fine cracks inside, and the defective rate was 0.2%.
Example 2. The difference from example 1 is:
in the step a, the length of the round steel is 2.33m, and the hardness is 207HBW;
in the step b, the product A is slowly heated to 1180 ℃;
in the step c, the rotating speed of the molybdenum plug is 50r/min, and the perforation speed is 0.71m/min;
in the step e, the temperature of the D product is kept at 280 ℃ when the hot rolling is finished.
In the step f, the temperature of the product E is kept at 280 ℃.
After 500 finished products of example 2 were examined, the number of surface cracked finished products was zero, and ultrasonic flaw detection was performed, 7 finished products had fine cracks inside, and the defective rate was 1.4%.
Example 3. The difference from example 1 is:
in the step a, the length of the round steel is 2.68m, and the hardness is 255HBW;
in the step b, the product A is slowly heated to 1220 ℃;
in the step c, the rotating speed of the molybdenum plug is 70r/min, and the perforation speed is 0.76m/min;
in the step e, the product D is kept at 300 ℃ when the hot rolling is finished.
In the step f, the temperature of the product E is kept at 300 ℃.
After 500 finished products of example 3 were examined and the number of surface cracked finished products was 1, ultrasonic flaw detection was performed, and 4 finished products had fine cracks inside and a defective rate of 1%.
The three examples described above are compared as follows:
example 4. The difference from example 1 is:
in the step a, the diameter of the round steel is 150 or 190mm, the length of the round steel is 1.8 or 3m, and the diameter of the central hole is 45 or 55m.
The invention has the advantage of forming the high-hardness material into the seamless steel pipe, and is particularly suitable for forming Cr12MoV into the seamless steel pipe.
Claims (4)
1. A seamless steel tube forming process is characterized in that: comprises the following steps of (a) carrying out,
a. making central hole on the round steel to obtain product A,
b. heating product A to a temperature within 100 deg.C of liquidus temperature at a heating speed of less than 6 deg.C/min, maintaining the temperature to obtain product B,
c. extruding the molybdenum plug through the center hole of the B product by using a puncher, lengthening the length of the B product, increasing the diameter of the center hole, rotating at 50-70r/min, guiding the B product by a guide plate of the puncher, lengthening the B product in a fixed direction to obtain a C product,
d. putting round rod-shaped inner mold into product C to obtain product D,
e. continuously hot rolling the outer peripheral surface of the product D by using a hot rolling mill and an external mold to reduce the outer diameter and lengthen the length of the product D, naturally cooling the product D to 240-300 ℃ during hot rolling to obtain a product E,
f. extracting the inner mold from the product E to obtain a product F,
g. spheroidizing and annealing the F product to obtain a finished product;
in the step a, the diameter of the round steel is 150-190mm, the length of the round steel is 1.8-3m, the hardness of the round steel is 207-255HBW, and the diameter of the central hole is 45-55mm;
in the step a, the round steel is made of Cr12MoV, and in the step b, the product A is heated to 1180-1220 ℃;
in the step c, the rotating speed of the molybdenum plug is 60r/min, the perforation speed is 0.73m/min, or the rotating speed of the molybdenum plug is 50r/min, the perforation speed is 0.71m/min, or the rotating speed of the molybdenum plug is 70r/min, and the perforation speed is 0.76m/min.
2. The seamless steel tube forming process according to claim 1, characterized in that: the diameter of the round steel is 170mm, and the diameter of the central hole is 50mm.
3. The seamless steel tube forming process according to claim 1, characterized in that: and in the step c, the roller of the perforator is cooled in a timed and directional mode.
4. The seamless steel tube forming process according to claim 1, characterized in that: and (3) performing timed and directional cooling on the roller of the hot rolling mill.
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| CN202110073289.XA CN112893470B (en) | 2021-01-20 | 2021-01-20 | Seamless steel tube forming process |
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| CN202110073289.XA CN112893470B (en) | 2021-01-20 | 2021-01-20 | Seamless steel tube forming process |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102527722A (en) * | 2011-12-31 | 2012-07-04 | 湖北新冶钢有限公司 | Perforating and rolling equipment and method of high-alloy and hard-deformation seamless steel tube |
| CN103464507A (en) * | 2013-07-25 | 2013-12-25 | 攀钢集团成都钢钒有限公司 | Production method for high-precision austenite seamless steel pipe |
| CN103736734A (en) * | 2013-12-30 | 2014-04-23 | 江苏常宝钢管股份有限公司 | Process of preparing high-chromium alloy supper 13-Cr seamless steel tubes through CPE (cross-roll piercing and elongation) hot rolling mill |
| CN106238465A (en) * | 2016-08-11 | 2016-12-21 | 攀钢集团成都钢钒有限公司 | A kind of preparation method of PH stainless steel seamless steel pipe |
| CN106269980A (en) * | 2016-08-30 | 2017-01-04 | 安吉县鹏大钢管有限公司 | A kind of preparation technology of seamless steel pipe |
-
2021
- 2021-01-20 CN CN202110073289.XA patent/CN112893470B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102527722A (en) * | 2011-12-31 | 2012-07-04 | 湖北新冶钢有限公司 | Perforating and rolling equipment and method of high-alloy and hard-deformation seamless steel tube |
| CN103464507A (en) * | 2013-07-25 | 2013-12-25 | 攀钢集团成都钢钒有限公司 | Production method for high-precision austenite seamless steel pipe |
| CN103736734A (en) * | 2013-12-30 | 2014-04-23 | 江苏常宝钢管股份有限公司 | Process of preparing high-chromium alloy supper 13-Cr seamless steel tubes through CPE (cross-roll piercing and elongation) hot rolling mill |
| CN106238465A (en) * | 2016-08-11 | 2016-12-21 | 攀钢集团成都钢钒有限公司 | A kind of preparation method of PH stainless steel seamless steel pipe |
| CN106269980A (en) * | 2016-08-30 | 2017-01-04 | 安吉县鹏大钢管有限公司 | A kind of preparation technology of seamless steel pipe |
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