Hot continuous rolling process for high-alloy seamless steel pipe

Abstract

The invention discloses a hot continuous rolling process for a high-alloy seamless steel pipe. The hot continuous rolling process is characterized by comprising the following steps of: heating in an annular furnace, perforating, continuously rolling, removing a pipe, sizing (tension reducing) diameter, cooling in a cooling bed and finishing, through preparation of a hot tool before rolling, establishment of an annular furnace heating system and technological parameters of key procedures such as perforation, continuous rolling, sizing and gang sawing, the surface quality and the geometric dimension of the hot-rolled steel pipe meet the standard requirements of users, and the hot-rolled steel pipe has good popularization value.

Description

Technical Field

[0001] The invention belongs to the technical field of metal technology, and in particular relates to a hot continuous rolling process for a high-alloy seamless steel pipe. Background Art

[0002] High alloy seamless steel pipe is a kind of pipe material with excellent mechanical properties and corrosion resistance, which is widely used in various industrial fields. Because of its higher strength and reliability, and no internal welds, this kind of seamless pipe can be used as a pipe that withstands higher pressure. In recent years, with the increasingly severe well conditions and use environment, the demand for high alloy seamless steel pipe has continued to increase. Summary of the invention

[0003] The purpose of the present invention is to provide a hot continuous rolling process for high alloy seamless steel pipes. The surface quality and geometric dimensions of the steel pipes after hot rolling meet the standard requirements of users and have good promotion value.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention discloses a hot continuous rolling process for high alloy seamless steel pipe, comprising: heating in an annular furnace → punching → continuous rolling → pipe stripping → sizing → cooling bed → finishing; wherein:

[0006] The heating system of the annular furnace is shown in the following table:

[0007]

[0008]

[0009] Annular furnace charging method: 5 blocking billets are placed before loading, 1 blocking billet is placed between the first and second billets, and from the second billet onwards, each billet is left empty for checking the top and guide plate, and the last 20 billets are tail billets;

[0010] perforation:

[0011] Tool preparation: Plug: Ф175 containing cobalt and thread; Plug: Φ171; Guide plate: 100 old guide plates after rolling and grinding; Glass powder is applied to the plug and guide plate before going online; The straightness and length of the plug are measured in advance, and it is put on line for trial use to observe the trend of the wall thickness curve; The actual guide distance is measured before rolling the high-alloy seamless steel pipe; Contact the annular furnace in advance whenever there is an empty material position. If the guide plate needs to be checked, notify the annular furnace to transfer the material to the back of the partition wall; The length of the rough pipe is 500mm longer than the process card requires. If the second bite is difficult, the front pressure reduction rate can be increased to ensure normal bite; When the rough pipe reaches the return roller in front of the holding roller, the holding roller is opened to prevent the rough pipe from shaking and irregular head; The overload of the punching machine is released to 150, and the power-off delay is increased to 6 seconds; The centering opening load in the machine is reduced to 5%. The steel throwing signal is adjusted from 10% to 5%;

[0012] When rolling starts, the cooling water of the guide plate is turned off, and the cooling water is turned on automatically after the production is in progress; when rolling starts, the water of the main machine is turned on automatically, and the water of the main machine for perforation is turned on normally after the production is in progress; the cooling water of the plug is given; the grinding wheel and the spool are prepared in advance, and the guide plate is quickly ground during the empty material position time; when rolling with cobalt-containing plugs, a dedicated person is arranged in the background to monitor the plug surface;

[0013] Continuous rolling: When rolling the first roll, the gap between the continuous rolling rolls is 1.5mm, and then gradually pressed into place; the mandrel is preheated in the furnace two hours in advance to ensure the temperature of the mandrel; a mandrel of specification 168.8 is used, and the mandrel number is used according to the instructions for use of the mandrel, with 6 used and 2 reserved; the graphite spraying length is increased by 0.5 meters to avoid the second half of the working section from not being able to spray graphite; the continuous rolling descaling water is turned off, and the cooling water of the continuous rolling main machine is turned off; the rolling force of each continuous rolling is adjusted in time if the rolling force is abnormal; the grinding wheel and the spool are prepared in advance, and the roller edge of the tube stripping machine is inspected and ground during the empty material position time;

[0014] Sizing: Reduce the overall speed of sizing by 20% when rolling, turn off all water in the rolling mill and auxiliary machines; use 177.8*12.65 buckle frame; turn off roller cooling water and descaling water; check and grind rollers and steel wires before rolling; check the quality of internal and external surfaces first after rolling; prepare the grinding wheel spool in advance, and use the empty material position time to check and grind the sizing roller edge; empty the large cooling bed step by step, and place all the other parts except the sampling tube at the south end of the cooling bed, and close the door in advance;

[0015] Pipe row saw: The saw machine uses a new large-diameter saw blade with a bevel of ≤2mm and no steps. Before cutting, verify whether the large cooling bed number is clear, and re-mark the number in the middle part of the pipe body corresponding to the large cooling bed number. Set the saw machine speed to 120 and the feed rate to 0.05. Manually operate the roller table, clamp the pipe row after it is completely against the fixed-length trolley, and then lift the trolley to prevent short length. Grind the unloading arm and bull horn before production.

[0016] Furthermore, the production rhythm is 90 seconds. When rolling starts, one piece is produced first, and then it will continue to be produced if there is no problem after perforation and continuous rolling.

[0017] Furthermore, during the production process, the production may be stopped for more than 30 minutes due to equipment and other reasons. When rolling is started, the furnace temperature will be reduced by 30 to 50°C.

[0018] Furthermore, when the glass powder is coated at 850°C, in order to ensure the spraying effect and uniformity, the coating is carried out by adding water.

[0019] Furthermore, in order to prevent the coating from falling off during transportation, the mandrel is directly hoisted onto the rolling line.

[0020] Furthermore, the thickness measurement system starts the 360° mode to detect the distribution of the horizontal and vertical roller pressure. When the wall thickness feedback is close to a full circle, the single-point wall thickness uniformity trend is observed.

[0021] Furthermore, the large cooling bed is numbered one by one using high temperature chalk according to the rolling sequence.

[0022] Compared with the prior art, the beneficial technical effects of the present invention are:

[0023] Through the preparation of hot tools before rolling, the key process parameters such as ring furnace heating system, piercing, continuous rolling, sizing, and gang sawing are formulated. The surface quality and geometric dimensions of the steel pipe after hot rolling meet the user's standard requirements and have good promotion value

[0024] Check the quality of the inner and outer surfaces of the pipe body. Within 100mm of the head ends of the first two pipes, there is a slight inward fold, and the second pipe has an external spiral. The quality of the inner and outer surfaces of the following steel pipes is good. DETAILED DESCRIPTION

[0025] A high alloy seamless steel pipe hot rolling process, comprising:

[0026] Use 6 Φ200mm round billets, the chemical composition is shown in Table 1:

[0027] Table 1 Chemical composition of blank (%)

[0028] C Si Mn P S Cu Ni+Cr+Mo+V+Nb Al ≤0.05 0.15-0.65 0.3-0.8 ≤0.020 ≤0.008 ≤0.2 20-25 ≤0.04

[0029] Rolling specification Ф177.8*12.65mm seamless steel pipe, finished pipe geometric size requirements, see Table 2:

[0030] Table 2 Geometrical dimension requirements of steel pipes

[0031] Serial number project Require 1 Outside diameter tolerance -0.2%D~+1.0%D; 2 Wall thickness tolerance -10.0％t； 3 Wall thickness unevenness ≤15.0％ 4 Pipe body out-of-roundness ≤0.6%(D:127.00mm~339.72mm);

[0032] Rolling process: heating in annular furnace → piercing → continuous rolling → tube removal → sizing (stretching and reducing) → cooling bed → finishing.

[0033] 1. Ring furnace

[0034] 1.1 Heating temperature:

[0035] Table 3 Ring furnace heating system

[0036]

[0037]

[0038] 1.2 Empty rolling furnace (turn on the fan), as the billets in each zone are emptied, the burner is closed and the temperature begins to drop. Use a handheld thermometer (blackness coefficient 0.73) to measure the furnace bottom temperature. Before the high-alloy seamless steel pipe is loaded into the furnace, 5 billet stoppers are placed, and 1 billet stopper is placed between the first and second billets. From the second billet onwards, each billet is emptied for one step to check the top head and guide plate, and the last 20 billet stoppers are placed (for burning billets).

[0039] 1.3 The production rhythm is 90 seconds. When rolling starts, one tube is produced first. After the perforation and continuous rolling, the tube can be produced again if there is no problem. 1.4 When the empty material position is noticed, attention should be paid to the preparation of the subsequent units at any time. It is not allowed to wait for the discharge at the furnace door in advance to prevent the low temperature of the first tube from causing a large perforation load or large shaking of the tube.

[0040] 1.5 After the empty material position is completed, the rolling mill will first discharge one piece, and the material will be poured behind the partition wall, and then the material will be discharged continuously after the perforation notification;

[0041] 1.6 During the production process, if the equipment and other reasons may cause the production to stop for more than 30 minutes, the furnace temperature will be reduced by 30 to 50°C when rolling begins.

[0042] 2. Perforation

[0043] 2.1 Tool Preparation

[0044] 2.1.1 Head: Φ175 with cobalt and thread; Ejector rod: Φ171; Guide plate: 100 old guide plates after rolling and grinding;

[0045] 2.1.2 The mandrel and guide plate are coated with glass powder before going online; the glass powder is 850℃ (600 mesh). When coating the glass powder, in order to ensure the spraying effect and uniformity, the coating is carried out by adding water. In order to prevent the coating from falling off during transportation, the mandrel is directly hoisted to the rolling line;

[0046] 2.1.3 Measure the straightness and length of the ejector rod in advance, put it on line for trial use, and observe the trend of the wall thickness curve;

[0047] 2.1.4 Rolling of drums is about 3000 pieces.

[0048] 2.2 Measure the actual lead length of high alloy seamless steel pipe before rolling.

[0049] 2.3 Contact the annular furnace in advance whenever there is an empty material position. If you need to check the guide plate, notify the annular furnace to transfer the material behind the partition wall;

[0050] 2.4 The length of the rough tube is 500mm longer than the requirement of the process card. If the secondary bite is difficult, the front pressure reduction rate can be increased to ensure normal bite;

[0051] 2.5 When the wool tube reaches the return roller in front of the holding roller, the holding roller is opened to prevent the wool tube from shaking and the head is irregular;

[0052] 2.6 The overload of the punching machine is released to 150, and the power-off delay is increased to 6 seconds. The centering load inside the machine is reduced to 5%. The steel throwing signal is adjusted from 10% to 5%;

[0053] 2.7 The cooling water of the guide plate is closed when rolling, and the cooling water is automatically turned on after the production is in progress. The water of the main machine is automatically turned on when rolling is started, and the water of the main machine is always turned on after the perforation is in progress. The cooling water of the header is given;

[0054] 2.8 Prepare the grinding wheel and spool in advance, and use the empty material time to quickly grind the guide plate;

[0055] 2.9 When using cobalt-containing plugs for rolling, a dedicated person is arranged in the background to monitor the plug surface;

[0056] 2.10 Use high steel grade borax, the melting point of borax is 750℃.

[0057] 3. Continuous rolling

[0058] 3.1 Start rolling the first roll, and let the gap between the continuous rolls be 1.5mm, and then gradually press them into place;

[0059] 3.2 The core rod should be preheated in the furnace two hours in advance to ensure the core rod temperature;

[0060] 3.3 Use 168.8 specification mandrels. The mandrels should be used according to the mandrel instructions. Use 6 and spare 2.

[0061] 3.4 Increase the graphite spraying length by 0.5 meters to avoid the graphite not being sprayed in the second half of the working section;

[0062] 3.5 Turn off the descaling water of the continuous rolling mill and the cooling water of the main machine of the continuous rolling mill;

[0063] 3.6 Check the rolling force of each continuous rolling mill. If the rolling force is abnormal, adjust it in time.

[0064] 3.7 Prepare the grinding wheel and spool in advance, and use the empty material time to inspect and grind the roller edge of the tube stripping machine;

[0065] 3.8 The thickness measurement system starts the 360° mode to detect the distribution of the horizontal and vertical roller pressure. When the wall thickness feedback is close to a full circle, observe the trend of the single-point wall thickness uniformity;

[0066] 3.9 The continuous rolling mill frame uses about 1,000 old rollers to ensure that they are rough enough. And the roller diameter is large;

[0067] 4. Calibration

[0068] 4.1 Reduce the overall rolling and sizing speed by 20% and shut off all water in the rolling mill and auxiliary machines;

[0069] 4.2 Use 177.8*12.65 special buckle rack;

[0070] 4.3 The roller cooling water is turned off, and the descaling water is turned off;

[0071] 4.4 Check and grind the roller table and the steel wire before rolling;

[0072] 4.5 After rolling, first check the quality of the inner and outer surfaces;

[0073] 4.6 Prepare the grinding wheel spool in advance and use the empty material position time to inspect and grind the sizing roller edge;

[0074] 4.7 The large cooling bed is empty one step at a time. Except for the sampling tube, all other items are placed at the south end of the cooling bed and the door is closed in advance;

[0075] 4.8 The large cooling bed is numbered one by one using high temperature chalk according to the rolling sequence (1 meter away from the head or tail end)

[0076] 5. Pipe Gang Saw

[0077] 5.1 The saw machine uses a new large-diameter saw blade with a bevel of ≤2mm and no steps;

[0078] 5.2 Before cutting, verify whether the large cooling bed number is clear, and re-mark the number corresponding to the large cooling bed number in the middle part of the pipe body;

[0079] 5.3 The saw speed is set to 120 and the feed rate is set to 0.05;

[0080] 5.4 Manually operate the roller table, clamp the pipe row after it completely supports the sizing trolley, and then lift the trolley to prevent short length;

[0081] 5.5 Grind the unloading arm, horn, etc. before production;

[0082] 5.6 All production is done in-line.

[0083] 6. Conclusion

[0084] 6.1 Surface quality

[0085] Check the quality of the inner and outer surfaces of the pipe body. The first two pipes have a slight inward bend within 100mm of the head end, and the second pipe has an external spiral. The inner and outer surface quality of the rear steel pipe is good.

[0086] 6.2 Geometric dimensions

[0087] Table 4 External diameter measurement records

[0088]

[0089] Table 5 Wall thickness measurement records

[0090]

[0091] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A hot rolling process for high alloy seamless steel pipe, characterized in that: include: Ring furnace heating → piercing → continuous rolling → tube removal → sizing → cooling bed → finishing; Among them: The heating system of the annular furnace is shown in the following table: Annular furnace charging method: 5 blocking billets are placed before loading, 1 blocking billet is placed between the first and second billets, and from the second billet onwards, each billet is left empty for checking the top and guide plate, and the last 20 billets are tail billets; perforation: Tool preparation: Plug: Ф175 containing cobalt and thread; Plug: Φ171; Guide plate: 100 old guide plates after rolling and grinding; Glass powder is applied to the plug and guide plate before going online; The straightness and length of the plug are measured in advance, and it is put on line for trial use to observe the trend of the wall thickness curve; The actual guide distance is measured before rolling the high-alloy seamless steel pipe; Contact the annular furnace in advance whenever there is an empty material position. If the guide plate needs to be checked, notify the annular furnace to transfer the material to the back of the partition wall; The length of the rough pipe is 500mm longer than the process card requires. If the second bite is difficult, the front pressure reduction rate can be increased to ensure normal bite; When the rough pipe reaches the return roller in front of the holding roller, the holding roller is opened to prevent the rough pipe from shaking and irregular head; The overload of the punching machine is released to 150, and the power-off delay is increased to 6 seconds; The centering opening load in the machine is reduced to 5%. The steel throwing signal is adjusted from 10% to 5%; When rolling starts, the cooling water of the guide plate is turned off, and the cooling water is turned on automatically after the production is in progress; when rolling starts, the water of the main machine is turned on automatically, and the water of the main machine for perforation is turned on normally after the production is in progress; the cooling water of the plug is given; the grinding wheel and the spool are prepared in advance, and the guide plate is quickly ground during the empty material position time; when rolling with cobalt-containing plugs, a dedicated person is arranged in the background to monitor the plug surface; Continuous rolling: When rolling the first roll, the gap between the continuous rolling rolls is 1.5mm, and then gradually pressed into place; the mandrel is preheated in the furnace two hours in advance to ensure the temperature of the mandrel; use a 168.8 specification mandrel, and use the mandrel number as required by the mandrel instructions, with 6 in reserve for 2; increase the graphite spraying length by 0.5 meters to avoid the latter half of the working section from not being able to spray graphite; turn off the continuous rolling descaling water, and turn off the cooling water of the continuous rolling main machine; adjust the rolling force of each roll, and adjust it in time if the rolling force is abnormal; prepare the grinding wheel and the spool in advance, and use the empty material position time to check and grind the roll edge of the tube stripping machine; Sizing: Reduce the overall speed of sizing by 20% when rolling, turn off all water in the rolling mill and auxiliary machines; use 177.8*12.65 buckle frame; turn off roller cooling water and descaling water; check and grind rollers and steel wires before rolling; check the quality of internal and external surfaces first after rolling; prepare the grinding wheel spool in advance, and use the empty material position time to check and grind the sizing roller edge; empty the large cooling bed step by step, and place all the other parts except the sampling tube at the south end of the cooling bed, and close the door in advance; Pipe row saw: The saw machine uses a new large-diameter saw blade with a bevel of ≤2mm and no steps. Before cutting, verify whether the large cooling bed number is clear, and re-mark the number in the middle part of the pipe body corresponding to the large cooling bed number. Set the saw machine speed to 120 and the feed rate to 0.

05. Manually operate the roller table, clamp the pipe row after it is completely against the fixed-length trolley, and then lift the trolley to prevent short length. Grind the unloading arm and bull horn before production.

2. The hot rolling process for high alloy seamless steel pipe according to claim 1 or 2, characterized in that: The production rhythm is 90 seconds. When rolling starts, one piece is produced first, and then it will continue to be produced after there are no problems after perforation and continuous rolling.

3. The hot rolling process for high alloy seamless steel pipe according to claim 1 or 2, characterized in that: During the production process, equipment problems may cause production downtime for more than 30 minutes. When rolling begins, the furnace temperature will be reduced by 30 to 50°C.

4. The hot rolling process for high alloy seamless steel pipe according to claim 3, characterized in that: When glass powder is coated at 850℃, in order to ensure the spraying effect and uniformity, the coating is carried out by adding water.

5. The hot rolling process for high alloy seamless steel pipe according to claim 1, characterized in that: To prevent the coating from falling off during transportation, the mandrel is directly lifted onto the rolling line.

6. The hot rolling process for high alloy seamless steel pipe according to claim 1, characterized in that: The thickness measurement system starts the 360° mode to detect the distribution of the horizontal and vertical roller pressure. When the wall thickness feedback is close to a full circle, the single-point wall thickness uniformity trend is observed.

7. The hot rolling process for high alloy seamless steel pipe according to claim 1, characterized in that: The large cooling beds are numbered one by one using high-temperature chalk according to the rolling sequence.

Images