CN114350923A - Method for heating rare earth-containing 5Cr low-carbon medium alloy steel round pipe blank by adopting annular furnace - Google Patents
Method for heating rare earth-containing 5Cr low-carbon medium alloy steel round pipe blank by adopting annular furnace Download PDFInfo
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Abstract
The invention discloses a method for heating a low-carbon medium alloy steel round pipe blank containing rare earth 5Cr by adopting an annular furnace, which mainly comprises the following production processes of heating the round pipe blank, perforating the round pipe blank to form a tubular billet, hot continuous rolling the tubular billet to form a pierced billet, and reducing the tensile force of the pierced billet to form a rolled seamless pipe. The invention aims to provide a method for heating a rare earth-containing 5Cr low-carbon medium alloy steel round pipe blank by adopting a ring furnace, wherein the temperature of the rare earth-containing 5Cr low-carbon medium alloy steel round pipe blank heated by the method is uniform from inside to outside and from front to back, the burning loss is less, the plasticity is high, and the thermal defect is effectively avoided.
Description
Technical Field
The invention relates to a method for heating a low-carbon medium alloy steel round pipe blank containing rare earth 5Cr by adopting a ring furnace.
Background
The rare earth 5 Cr-containing low-carbon medium alloy steel round pipe blank is a raw material which is independently researched and developed by steel cladding and is used for manufacturing a special oil casing pipe for resisting carbon dioxide and hydrogen sulfide corrosion, an annular furnace is needed to heat the rare earth 5 Cr-containing low-carbon medium alloy steel round pipe blank in the initial stage of pressure rolling, the purpose of heating is to improve the plasticity of steel, reduce the denaturation resistance and provide good denaturation conditions for rolling, and therefore, the heating of the round pipe blank is particularly important in the manufacturing process of the oil casing pipe. A circular tube blank of low-carbon medium alloy steel containing rare earth and 5Cr is heated by adopting an annular furnace, the heating temperature is accurate at first, and the tube blank is ensured to be perforated and deformed in a temperature range with the best perforability. Secondly, the heating temperature is consistent, the male and female surfaces are stopped, and the size and the quality of the inner and outer surfaces of the perforated capillary are guaranteed. Thirdly, the heating time is reasonably controlled, so that the temperature of the round pipe blank from the surface to the core is uniform, and meanwhile, serious burning loss and serious oxidation cannot be caused. Finally, the heating process must be reasonable and feasible, is easy to operate on site, and avoids the heating defects such as hot cracks, overheating and overburning. The technology of heating carbon manganese steel and low alloy steel by adopting an annular furnace for ladle steel is very mature, the medium and high alloy steel is changed due to chemical components, material conductivity, density and the like, and the condition that the circular tube blank does not reach the requirement of perforation after being heated because the existing process is adopted to heat the rare earth-containing 5Cr low carbon medium alloy steel circular tube blank has certain mismatching.
Through search, three patents in the literature are found to be most relevant to the technology, and the specific contents are as follows:
document 1 is a heating process of a hot-rolled pipe blank (patent application No. CN201010110235.8), which provides a circular furnace heating process of a hot-rolled pipe blank, and the temperature ranges and times of a preheating section, a heating section and a heating section are respectively given, and the temperature ranges outside the soaking section, the soaking section and the soaking section are given, and different internal heterodyne temperatures are adopted in the soaking section to ensure that the head temperature of the hot-rolled pipe blank out of the furnace is lower than the tail temperature, so that the head and tail temperatures of the pipe blank entering a continuous rolling mill are uniform, better conditions are provided for the rolling of the continuous rolling mill, and the quality and yield of the pipe blank are effectively improved. However, the specific heating process provided by the patent is only suitable for heating carbon manganese steel or low alloy steel round pipe billets.
The document 2 is a heating control method (patent application number: CN201610353484.7) for a 16Mn seamless steel tube blank, and the document provides a method for heating the 16Mn seamless steel tube blank by using an annular heating furnace, wherein the heating temperature requirement of a preheating section is not higher than 700 ℃, the heating temperature of a low-temperature heating section is 800 ℃ to 1100 ℃, the heating temperature of a high-temperature heating section is 1050 ℃ to 1290 ℃, and the heating temperature of a soaking section is 1260 ℃ to 1300 ℃. The method can eliminate the defects of low 16Mn yield strength performance index. The higher heating and soaking temperature of the process is not suitable for producing the low-carbon medium alloy steel seamless pipe containing the rare earth 5 Cr.
Document 3 is a seamless steel tube blank heating process (patent application No. CN201410644391.0), which provides various links of the seamless steel tube blank heating process, and provides heating temperatures for high-carbon low-alloy 55SiMnMo and 60Si2Mn, and the provided operational points of various links of the tube blank heating process flow can be considered, but the provided high-carbon low-alloy steel heating temperatures are not suitable for low-carbon medium-alloy steel.
Disclosure of Invention
The invention aims to provide a method for heating a rare earth-containing 5Cr low-carbon medium alloy steel round pipe blank by adopting a ring furnace, wherein the temperature of the rare earth-containing 5Cr low-carbon medium alloy steel round pipe blank heated by the method is uniform from inside to outside and from front to back, the burning loss is less, the plasticity is high, and the thermal defect is effectively avoided.
In order to solve the technical problems, the invention adopts the following technical scheme:
the invention relates to a method for heating a low-carbon medium alloy steel round pipe blank containing rare earth 5Cr by adopting an annular furnace, wherein the main production process for rolling the low-carbon medium alloy steel round pipe blank containing the rare earth 5Cr into a seamless pipe comprises the steps of heating the round pipe blank, perforating the round pipe blank to form a tubular billet, hot continuous rolling the tubular billet to form a pierced billet, and reducing the tensile force of the pierced billet to form a rolled seamless pipe; the method specifically comprises the following steps:
s1, determining the heating temperature of the round tube blank of the low-carbon medium-alloy steel containing the rare earth 5Cr, wherein the process parameters are closely related to the chemical components of the round tube blank of the low-carbon medium-alloy steel containing the rare earth 5Cr, and the heating temperature of the tube blank is required to ensure that metal is always in the austenite structure temperature range under the states of best plasticity and minimum deformation resistance in the whole denaturation process from initial rolling to final rolling of the tube blank. The heating temperature is determined mainly according to the liquidus temperature of the low-carbon medium-alloy steel containing rare earth 5Cr, a continuous cooling structure transformation curve (CCT), the plastic deformation capacity and the deformation resistance strength of different temperature sections, and the heating temperature is determined by combining the specifications of a pipe blank, a hollow billet, a pierced billet and a rolled pipe and the temperature change from piercing continuous rolling to sizing;
s2, determining the heating speed, wherein the heating speed of the tube blank refers to the thickness of the tube blank heated along the radial direction of the tube blank in unit time, and for convenience of calculation in the industry, the time required for heating the tube blank with unit thickness to the temperature required by the process is usually adopted to represent the heating speed; the determination of the process parameters is mainly influenced by the thermal conductivity and the heating temperature of the heating material, the heating speed is reduced along with the reduction of the thermal conductivity of the material under the condition of certain heating temperature, and the thermal conductivity of the material is different due to different chemical components, high-temperature tissues of the material and the content of nonmetallic inclusions in the material; the heating speed of the rare earth-containing 5Cr low-carbon medium alloy steel round pipe billet is determined according to the self thermal conductivity and the production efficiency;
s3, determining the heating time, wherein the heating time required by the temperature required by the round tube blank heating process is inversely proportional to the heating speed, and the faster the heating speed is, the shorter the heating time is; in addition, factors such as the size, the heating method, the fuel type and the like of the heating tube blank are considered in the heating time; in actual production, the heating time of the round pipe blank is generally calculated by an empirical formula, in addition, in order to improve the temperature uniformity of the round pipe blank, the heating time is generally prolonged, and the actual heating time of the round pipe blank is 25-30% longer than the time calculated by the empirical formula;
s4, if the round pipe blank is directly put into the process design temperature environment, the heating degree is 1100-1300 ℃ under the normal condition.
Furthermore, the actual heating time of the round pipe blank is 30% longer than the time calculated by an empirical formula.
Further, the heating temperature of the low-carbon medium alloy steel round pipe blank containing the rare earth 5Cr is 1225-1250 ℃.
Compared with the prior art, the invention has the beneficial technical effects that:
the rare earth-containing 5Cr low-carbon medium alloy steel round pipe blank heated by the method has the advantages of uniform temperature from inside to outside and from front to back, less burning loss, high plasticity and effective avoidance of thermal defects.
Detailed Description
The invention is described in detail with reference to examples 1 to 3 of low carbon medium alloy steel round pipe billets containing rare earth 5Cr, examples 1 to 3 of which are all the same in chemical composition, metallurgical quality, round pipe billet length, ring furnace conditions and round pipe billet distribution rules except that the diameter of the round pipe billet is different and the rolled seamless pipe is different in specification, which is shown in table 1.
TABLE 1 examples of the embodiment of the pipe blank and the specification of the seamless pipe after rolling
An excessively high heating temperature of the pipe blank causes quality problems such as overheating, overburning, steel sticking, decarburization and burning loss, so that the heating of the round pipe blank is generally about 200 ℃ lower than the solidification point of steel. The liquidus temperature of the material calculated by adopting the chemical components of the rare earth-containing 5Cr low-carbon medium alloy steel through an empirical formula is 1509 ℃, so the heating temperature of the round tube blank is controlled below 1300 ℃. Sampling, and measuring a CCT curve of the low-carbon medium alloy steel containing rare earth 5Cr by using a thermal expansion instrument to obtain a complete austenitizing temperature Ac3 of 855 ℃; the circular tube blank has a certain distance from the outlet of the annular furnace to the front of the perforation and needs to be conveyed by a guide roller, the temperature of the circular tube blank is reduced by about 120-. The deformation resistance of the rare earth 5Cr low-carbon medium alloy steel is measured to be the lowest within the range of 1150-1300 ℃ by a gleeble thermal simulation experiment machine, the plastic deformation reaches more than 90% within the range of 1150-1250 ℃, therefore, the optimal piercing temperature is controlled to be 1150-1250 ℃, the temperature of the tube blank is required to be 1225-1300 ℃, and in order to meet the final rolling temperature and ensure good plastic deformation and low deformation resistance in the rolling process, the heating temperature of the rare earth 5Cr low-carbon medium alloy steel round tube blank can be determined to be 1225-1250 ℃.
The cast structure of the rare earth-containing 5Cr low-carbon medium alloy steel is a bainite structure, the transformation from the bainite structure to a martensite structure mainly occurs in the heating process, the structure transformation stress is generated, if the heating speed is too high, the thermal stress cannot be released in time, and the stress defect generation trend is greatly increased by overlapping the structure transformation stress. Therefore, a slow heating technique is used from the beginning to the end of the tissue transformation. In addition, since the heating time is inversely proportional to the heating speed, only the heating temperature is designed, the heating time can be calculated according to an empirical formula t ═ κ × D (where t is the heating time, κ is the heating time per unit thickness, medium alloy steel is generally 6.5-8.0min/cm, and D is the diameter of the round pipe blank), and in order to ensure the uniformity of the temperature of the round pipe blank, the actual heating time of the round pipe blank is generally prolonged by about 30% more than the time calculated by the empirical formula, and the theoretical heating time and the actual heating time of the round pipe blank of the rare earth-containing 5Cr low-carbon medium alloy round pipe blank in the embodiment 1 to the embodiment 3 are shown in table 2.
Table 2 shows the theoretical heating time and the actual heating time of the round pipe blank
| Blank outer diameter/mm | Theoretical heating time/min | Actual heating time/min | |
| Example 1 | 200 | 140 | 182 |
| Example 2 | 245 | 172 | 223 |
| Embodiment 3 | 270 | 189 | 245 |
Note: heating time per unit thickness was 7.0 min/cm.
The 35 m annular heating furnace comprises a furnace body and a rotary furnace bottom, the furnace body comprises 270 material levels from a charging port to a discharging port, wherein the number of effective material levels is 261, in order to ensure that the round pipe billet is gradually heated from a low level number to a high level number, six sections including a preheating section, a heating section, a soaking section and a soaking section are artificially divided, the inner side and the outer side of each section are respectively provided with a group of burners, each group of burners is controlled by a reversing valve, and the burners are sequentially and circularly combusted according to a set reversing period and a reversing interval. The heating temperature of the rare earth 5 Cr-containing low-carbon medium alloy round pipe blank is 1220-1250 ℃, the heating temperature of the rare earth 5 Cr-containing low-carbon medium alloy steel Ac1 is 784 ℃, the heating temperature of Ac3 is 855 ℃, rapid heating is adopted when the temperature is lower than the phase transition temperature, and the austenite transformation area is heated at a low speed, so that the heating speed can be properly improved, the heating speed is controlled by the number of material level divisions and the flow rate of a burner. The heating temperature and time for each section are shown in Table 3.
TABLE 3 heating temperature and time for each section
The implementation effect of the invention is as follows:
firstly, controlling the tapping temperature of a rare earth-containing 5Cr low-carbon medium alloy steel round pipe blank heated by adopting the heating process at 1250 +/-5 ℃ from top to bottom;
② the rare earth-containing 5Cr low-carbon medium alloy seamless tube produced by adopting the above heating process has good quality of inner and outer surfaces, the unevenness of wall thickness is not more than 10 percent, and the ovality is not more than 0.4'
The yield of the rare earth-containing 5Cr low-carbon medium alloy seamless tube produced by the heating process reaches more than 92 percent, and the production process is reasonable and smooth.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.
Claims (3)
1. A method for heating a low-carbon medium alloy steel round pipe blank containing rare earth and 5Cr by adopting an annular furnace is characterized by comprising the following steps of: the main production process of rolling the rare earth-containing 5Cr low-carbon medium alloy steel round pipe blank into a seamless pipe comprises the steps of heating the round pipe blank, perforating the round pipe blank to form a tubular billet, hot continuous rolling the tubular billet to form a pierced billet, and reducing the tension of the pierced billet to form a rolled seamless pipe; the method specifically comprises the following steps:
s1, determining the heating temperature of the round tube blank of the low-carbon medium-alloy steel containing the rare earth 5Cr, wherein the process parameters are closely related to the chemical components of the round tube blank of the low-carbon medium-alloy steel containing the rare earth 5Cr, and the heating temperature of the tube blank is required to ensure that metal is always in the austenite structure temperature range under the states of best plasticity and minimum deformation resistance in the whole denaturation process from initial rolling to final rolling of the tube blank. The heating temperature is determined mainly according to the liquidus temperature of the low-carbon medium-alloy steel containing rare earth 5Cr, a continuous cooling structure transformation curve (CCT), the plastic deformation capacity and the deformation resistance strength of different temperature sections, and the heating temperature is determined by combining the specifications of a pipe blank, a hollow billet, a pierced billet and a rolled pipe and the temperature change from piercing continuous rolling to sizing;
s2, determining the heating speed, wherein the heating speed of the tube blank refers to the thickness of the tube blank heated along the radial direction of the tube blank in unit time, and for convenience of calculation in the industry, the time required for heating the tube blank with unit thickness to the temperature required by the process is usually adopted to represent the heating speed; the determination of the process parameters is mainly influenced by the thermal conductivity and the heating temperature of the heating material, the heating speed is reduced along with the reduction of the thermal conductivity of the material under the condition of certain heating temperature, and the thermal conductivity of the material is different due to different chemical components, high-temperature tissues of the material and the content of nonmetallic inclusions in the material; the heating speed of the rare earth-containing 5Cr low-carbon medium alloy steel round pipe billet is determined according to the self thermal conductivity and the production efficiency;
s3, determining the heating time, wherein the heating time required by the temperature required by the round tube blank heating process is inversely proportional to the heating speed, and the faster the heating speed is, the shorter the heating time is; in addition, factors such as the size, the heating method, the fuel type and the like of the heating tube blank are considered in the heating time; in actual production, the heating time of the round pipe blank is generally calculated by an empirical formula, in addition, in order to improve the temperature uniformity of the round pipe blank, the heating time is generally prolonged, and the actual heating time of the round pipe blank is 25-30% longer than the time calculated by the empirical formula;
s4, if the round pipe blank is directly put into the process design temperature environment, the heating degree is 1100-1300 ℃ under the normal condition.
2. The method for heating the rare earth-containing 5Cr low-carbon medium alloy steel round pipe blank by using the annular furnace according to claim 1, which is characterized by comprising the following steps of: the actual heating time of the round pipe blank is 30% longer than the time calculated by an empirical formula.
3. The method for heating the rare earth-containing 5Cr low-carbon medium alloy steel round pipe blank by using the annular furnace according to claim 1, which is characterized by comprising the following steps of: the heating temperature of the low-carbon medium alloy steel round pipe blank containing the rare earth 5Cr is 1225-1250 ℃.
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Citations (4)
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|---|---|---|---|---|
| CN102228905A (en) * | 2011-04-03 | 2011-11-02 | 胡顺珍 | Production process of hot continuous rolling seamless steel tube with small caliber |
| WO2017050229A1 (en) * | 2015-09-24 | 2017-03-30 | 宝山钢铁股份有限公司 | Process for on-line quenching of seamless steel tube using waste heat and manufacturing method |
| CN108393355A (en) * | 2018-03-26 | 2018-08-14 | 天津商业大学 | A kind of manufacturing method of oil/gas well novel seamless steel tube |
| CN112853215A (en) * | 2021-01-06 | 2021-05-28 | 包头钢铁（集团）有限责任公司 | Preparation method of rare earth Ce-containing high-strength high-toughness high-collapse-resistance petroleum casing pipe |
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- 2021-12-03 CN CN202111464977.5A patent/CN114350923A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102228905A (en) * | 2011-04-03 | 2011-11-02 | 胡顺珍 | Production process of hot continuous rolling seamless steel tube with small caliber |
| WO2017050229A1 (en) * | 2015-09-24 | 2017-03-30 | 宝山钢铁股份有限公司 | Process for on-line quenching of seamless steel tube using waste heat and manufacturing method |
| CN108393355A (en) * | 2018-03-26 | 2018-08-14 | 天津商业大学 | A kind of manufacturing method of oil/gas well novel seamless steel tube |
| CN112853215A (en) * | 2021-01-06 | 2021-05-28 | 包头钢铁（集团）有限责任公司 | Preparation method of rare earth Ce-containing high-strength high-toughness high-collapse-resistance petroleum casing pipe |
Non-Patent Citations (1)
| Title |
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| 成海涛: "管坯加热工艺技术―《热轧无缝钢管实用技术》", 钢管, vol. 47, no. 4, pages 78 - 83 * |
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