Hot rolling method for thin-gauge iron-nickel-based alloy
By optimizing the hot rolling process, the problem of unstable production of thin-gauge iron-nickel-based alloys on the hot continuous rolling production line was solved, resulting in higher yield and production efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANXI TAIGANG STAINLESS STEEL CO LTD
- Filing Date
- 2026-02-09
- Publication Date
- 2026-04-14
AI Technical Summary
On the 2250 hot strip rolling production line, thin-gauge iron-nickel-based alloys suffer from problems such as transverse cracks during furnace loading, rolling cracks, deviation, and fractures during the rolling process, leading to unstable production and a high scrap rate, which affects production efficiency.
The hot rolling process is optimized by comprehensively controlling the planning, billet preparation, heating requirements, and process parameters during rolling, including unit transition, head and tail billet arrangement, heating temperature control, roughing and finishing rolling reduction ratio distribution, laminar cooling method, and coiling tension control.
It improves the rolling stability of iron-nickel based alloys, reduces scrap rate, saves time, and increases production efficiency and yield.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of hot-rolled strip technology and relates to a hot rolling method for thin-gauge iron-nickel-based alloys. Background Technology
[0002] Iron-nickel based alloy materials are widely used in machinery, metallurgy, chemical industry, food, home appliances, electric heating, resistance elements, and metal carriers for three-way catalytic converters for vehicle exhaust purification. They are generally made into resistance heating tapes, wires, and rods (foil thickness ≤ 0.2 mm, wire φ > 1 mm) using foil, coarse wire, and rod materials, and operate at a working temperature of 1000-1300℃.
[0003] Since the hot continuous rolling 2250 production line began producing approximately 3.0mm iron-nickel based alloys, it has encountered problems such as transverse cracks during furnace loading, edge cracks inside the furnace, cracks during rough rolling, hot coil box misalignment, F6-F7 misalignment and rolling damage, and breakage during coiling. The production process is unstable, and the frequency of scrap steel is high. Iron-nickel based alloys are brittle and prone to fracture. Once scrap steel is generated, the processing time is long, averaging about 180-210 minutes per batch, which reduces production efficiency.
[0004] Therefore, achieving stable rolling of thin-gauge iron-nickel-based alloys is an urgent task. Summary of the Invention
[0005] This invention proposes a stable rolling method for hot rolling of thin-gauge iron-nickel-based alloys. By comprehensively controlling the planning, billet preparation, heating requirements, and process parameters during rolling, the stability of iron-nickel-based alloys during rolling is improved, the shortcomings of existing rolling processes are solved, and the yield is increased.
[0006] This invention provides a hot rolling method for thin-gauge iron-nickel-based alloys. The rolling process includes comprehensive control planning, billet preparation, heating, rough rolling, hot coiling, finish rolling, layer cooling, and coiling, specifically including the following: (1) The unit transition, head and tail billet arrangement principles and thickness transition steps in the comprehensive control plan arrangement; (2) Controlling the heating temperature and furnace temperature ensures the quality of the billets produced from the furnace; (3) The roughing rolling adopts 7 passes, and the side guide opening is automatically reduced by 15-25mm after the roughing rolling load relay is turned on for 1 second; (4) The hot roll box adopts the method of correcting and increasing the gap between the bending rollers and lowering the unwinding 1B roller (by 10mm) to ensure stable and smooth unwinding production; (5) The reduction ratio distribution of F1-F7 mills in the finishing mill was optimized (F1-F2 increased by 5%; F5-F6 decreased by 3%), and the looper tension control was optimized and increased (the tension of loopers 1-6# was increased by 3%). The correction value of the F5-F6 roll shifting was 120mm-145mm, and the threading speed was limited to 6.0-6.3m / s to ensure the stability of finishing mill rolling; The finishing rolling process of this invention involves 7 finishing mills, denoted as F1 to F7 respectively.
[0007] (6) Optimize the laminar flow cooling method. The head 100-meter cooling section adopts a relatively fixed water spray control gain. The relatively fixed water spray is in groups 17-19, and the water ratio is 6 / 8 in the upper and lower sections. (7) The lead rate of the finishing mill exit roller table speed was increased by 12%, and the specific control of coiling tension threading and steel throwing was optimized.
[0008] The above content is further explained as follows: (1) Planning and arrangement: The number of chromium steel blocks of the same width in the front row of the iron-nickel-based alloy shall not exceed 30. The iron-nickel-based alloy shall be arranged in a maximum of two furnaces of 12 blocks at a time, and the entire rolling unit shall not exceed 70 blocks.
[0009] (2) Transition principle: Before rolling the iron-nickel-based alloy, use two chromium steels with thicknesses of 3.5 mm and 3.0 mm. The iron-nickel-based alloy is transitioned to the target thickness by adjusting the thickness of the first 2-3 pieces in a stepped manner. The difference between adjacent thicknesses is controlled within 0.35 mm. The third or fourth piece directly reaches the target thickness. The coiling temperature transition principle is to transition sequentially according to the target temperature +30℃, +20℃, and +10℃.
[0010] (3) Billet preparation: The billet loading temperature should be ≥250℃ (temperature measurement point: midpoint of the width of the slab), and the time from entering the warehouse to loading into the furnace should not exceed 1 hour. If the billet is transported in an insulated vehicle, it should be loaded into the furnace directly without touching the ground, and the surface of the billet should be inspected. If any defects that affect rolling are found, the billet should not be loaded into the furnace.
[0011] (4) Heating control: The specific temperatures of each heating section of the walking beam furnace are as follows: the preheating section temperature is 950±20℃, the first heating section temperature is 1130±20℃, the second heating section and the soaking section temperature is 1160±20℃; the target steel temperature is 1150±20℃; the total furnace dwell time is ≥200min, of which the preheating section time is 55-60min, the first heating section time is 50-55min, the second heating section time is 55-60min, and the soaking section time is 40-45min.
[0012] (5) Rough rolling: After the heated slab is descaled once, it is rough rolled. The rough rolling adopts seven rolling passes. The descaling at the inlet and outlet of the rough rolling is not used. The thickness of the intermediate slab is 30mm~32mm. The side guide allowance of the 4th to 7th rough rolling passes is 55mm. On this basis, it is reduced by 15mm-25mm.
[0013] (6) Hot rolling box: The hot rolling box is used after the intermediate billet is rolled in the rough rolling. When the hot rolling box is rolled, the gap between the bending rolls is set to 32mm. On this basis, it is increased by 5mm. The tail value is corrected to the position of 4-5 o'clock. When there is a curling head at the uncoiling head, the height of the 1B roll is reduced by 10mm.
[0014] (7) Finishing: The intermediate billet is rolled in a finishing mill. The finishing process of this invention involves 7 finishing mills, which are denoted as F1 to F7 respectively.
[0015] To prevent slippage at F7 before rolling, the process lubricant at F7 should be removed. The L2 (secondary process control system) optimizes the reduction rate of F5 to between 21% and 23%, F6 to between 15% and 17%, and F7 to between 10% and 13%. The threading speed of F6-F7 is appropriately increased by 0.5% from 6.0 m / s to ensure controlled steel pulling at F6-F7. The F5-F6 roll shifting is controlled with slight undulation at a range of 120mm-145mm.
[0016] (8) Laminar flow cooling: Laminar flow cooling adopts front-end cooling. No cooling water is used in the first 30m of the strip. The cooling section after the first 30m adopts a relatively fixed water spray control gain. Relatively fixed water spray control means fixing the water spray valve frame and the number of water sprays.
[0017] (9) Coiling: Increase the lead rate of the exit roller speed of the finishing mill by 10-12%, and manually increase the tension by 10-13% after the coiling is set up to avoid the strip from deviating further after it is unrolled on the roller. When throwing the F3 strip, manually reduce the tension by 10-12% to avoid the surface imprint caused by the strip folding due to the excessively fast throwing speed at the tail.
[0018] (10) The development of the pinch roll lifting function is to simultaneously meet the two conditions of the roll load connection and the auxiliary roll opening command signal after the strip head enters the coiler and establishes tension. The pinch roll lifts the roll gap to 3 times the current value. This avoids the pinch roll pressure from the strip waviness from increasing, which would cause the strip to break brittlely under stress.
[0019] The beneficial effects of this invention are: (1) As a high-chromium ferritic steel, iron-nickel based alloys tend to grow grains rapidly at high temperatures (>800℃). This invention prevents the billet from being held in the furnace for too long at high temperatures, resulting in central perforation and affecting the hot plasticity of the billet by controlling the heating temperature and heating time. (2) The present invention reduces the amount of deviation during unwinding by increasing the setting of the bending roller gap (32+5mm) and avoids the head lifting caused by excessive pressure on the insertion arm by reducing the height of the 1B roller; (3) This invention prevents deviation or rolling damage caused by unstable reduction rate and tension by reasonably controlling the finishing rolling reduction rate, tension and threading speed; (4) The present invention controls the length of the non-cooled section at the head by using a relatively fixed water spray (i.e., a fixed water spray valve frame and water spray quantity) to control the gain of the 100-meter cooling section at the head, thereby avoiding excessively low temperature control before the steel is coiled and bitten. (5) By controlling the tension of the steel throwing mill stand and the lead rate of the steel throwing exit roller table, this invention avoids the steel strip from deviating further after being unrolled on the roller table and avoids the folding and imprinting caused by the excessive speed of steel throwing. (6) By developing the pinch roll lifting function, this invention avoids the phenomenon that the strip will break brittlely after being subjected to force due to the increased pressure of the pinch roll before the wavy shape at the head of the strip is eliminated. Detailed Implementation
[0020] The present invention will be further illustrated by the following embodiments, but is not limited to the following embodiments.
[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to specific examples.
[0022] Example 1: The 0CR21AL6 used in the experiment of this invention has a thickness of 3.05 mm and a width of 1230 mm. The total number of iron-nickel based alloy rolling units is 39, including 9 Q235B units, 20 SUH409L units, and 10 0CR21AL6 units. The number of units with the same width as the iron-nickel based alloy is no more than 30 (width ≤ 1300 mm).
[0023] (1) Production organization: Personnel are arranged at the exit of the roughing mill to check for cracks. If longitudinal or transverse cracks are found, rolling is stopped and the plate is pushed off the mill in time, and it cannot be rolled into the finishing mill. Personnel are arranged at the front of the finishing mill to observe the plate shape. During the threading process, the changes in the plate shape of F1 / F2 are observed. During the process, the changes in the plate shape before and after F4 are monitored and the operators are informed in a timely manner.
[0024] (2) Transition principle: Before rolling 0CR21AL6, transition two SUH409L steels with a target finishing thickness of 3.5mm. After 0CR21AL6 is loaded into the furnace, modify the target finishing thickness of the first steel to 3.5mm and the target finishing thickness of the second steel to 3.25mm, and transition the two steels to the limit material of 3.05mm. At the same time, according to the furnace loading sequence, modify the coiling target temperature to 350℃, 340℃, and 330℃ for transition.
[0025] (3) Billet preparation: The billets are transported in insulated vehicles and loaded directly into the heating furnace without touching the ground. The loading temperature of the billets is 260±20℃.
[0026] (4) Heating control: The specific temperatures of each heating section of the walking beam furnace are as follows: preheating section temperature 950±20℃, first heating section temperature 1130±20℃, and second heating and soaking section temperatures controlled at 1160±20℃. The target steel temperature is 1150±20℃; the total furnace dwell time is 200min, of which the preheating section time is 55min, the first heating section time is 50min, the second heating section time is 55min, and the soaking section time is 40min.
[0027] (5) Rough rolling: After one main descaling pass, rough rolling is carried out in seven passes. No descaling is applied during the rolling process. By reasonably setting the reduction rate of each pass, the final thickness of the intermediate slab in the rough rolling is 30mm~32mm. During the rolling process, after the strip load relay is turned on for 1 second during the 4th to 7th passes of rough rolling, the side guide allowance is reduced by 15mm-25mm, as shown in Table 1.
[0028] Table 1
[0029] (6) Hot rolling box: After the intermediate billet is rolled by rough rolling, the hot rolling box is used. The gap between the bending rolls of the hot rolling box is increased by 3mm-5mm. The tail value is corrected to the 4-5 o'clock position, as shown in Table 2.
[0030] Table 2
[0031] (7) Finishing: The intermediate billet is rolled in the finishing mill. The F7 process lubrication is removed during the rolling process. The L2 (secondary control system) optimizes the F5 reduction rate range to 21%-23%, the F6 reduction rate range to 15%-17%, and the F7 reduction rate range to 10%-13%. The operator adjusts the F5 roll between 130mm-145mm and the F6 roll between 120mm-135mm to control the micro-wave. F6-F7 can be rolled by steel pulling. The threading speed is appropriately increased by 0.5%, and the tensions between the F1 and F7 stands are 8MPa, 12MPa, 14MPa, 16MPa, 18MPa, and 20MPa, respectively, as shown in Table 3 below.
[0032] Table 3
[0033] (8) Laminar flow cooling: Laminar flow cooling adopts front-end cooling. No cooling water is used in the first 30m of the strip. The cooling section after the first 30m adopts a relatively fixed water spray control gain. As shown in Table 4.
[0034] Table 4
[0035] (9) Coiling: The lead rate of the finishing mill exit roller table speed increased from 6.58 m / s to 7.3 m / s, and the manual tension after coiling was reduced from 23 N / mm. 2 Mentioning 26N / mm 2 To prevent the strip from deviating further after being unrolled on the roller conveyor, the tension during F3 strip throwing is reduced from 26 N / mm. 2 Manually reduce to 23 N / mm 2 To avoid surface imprints caused by excessively fast tail-end steel throwing speed resulting in strip folding.
[0036] (10) The development of the pinch roll lifting function is to simultaneously meet the two conditions of the roll load connection and the auxiliary roll opening command signal after the strip head enters the coiler and establishes tension. The pinch roll lifts the roll gap to 3 times the current value. This avoids the pinch roll pressure from the strip waviness from increasing, which would cause the strip to break brittlely under stress.
[0037] The actual data of heating and rough rolling of the 10 steel pieces described in the experiment are shown in Table 5, and the actual data of finish rolling are shown in Table 6.
[0038] Table 5
[0039] Table 6 .
[0040] Example 2: The 0CR18AL4RE used in the experiment of this invention has a thickness of 3.0 mm and a width of 1157 mm. The total number of iron-nickel based alloy rolling units is 55, including 8 Q235B units, 42 430 units, and 5 0CR18AL4RE units; and the number of units with the same width as the iron-nickel based alloy is no more than 30.
[0041] (1) Production organization: Personnel are arranged at the exit of the roughing mill to check for cracks. If longitudinal or transverse cracks are found, rolling is stopped and the plate is pushed off the mill in time, and it cannot be rolled into the finishing mill. Personnel are arranged at the front of the finishing mill to observe the plate shape. During the threading process, the changes in the plate shape of F1 / F2 are observed. During the process, the changes in the plate shape before and after F4 are monitored and the operators are informed in a timely manner.
[0042] (2) Transition principle: Before rolling 0CR18AL4RE, transition two pieces of 430 steel with a target finishing thickness of 3.2mm. After the 0CR18AL4RE is loaded into the furnace, modify the target finishing thickness of the first piece of steel to 3.4mm and the target finishing thickness of the second piece of steel to 3.2mm, and transition the two pieces to the limit material of 3.0mm. At the same time, according to the furnace loading sequence, modify the coiling target temperature to 350℃, 340℃, and 330℃ for transition.
[0043] (3) Billet preparation: The billets are transported in insulated vehicles and loaded directly into the heating furnace without touching the ground. The loading temperature of the billets is 260±20℃.
[0044] (4) Heating control: The specific temperatures of each heating section of the walking beam furnace are as follows: preheating section temperature 950±20℃, first heating section temperature 1130±20℃, and second heating and soaking section temperatures controlled at 1160±20℃. The target steel temperature is 1150±20℃; the total furnace dwell time is 220 min, of which the preheating section time is 60 min, the first heating section time is 55 min, the second heating section time is 60 min, and the soaking section time is 45 min.
[0045] (5) Rough rolling: After one main descaling pass, rough rolling is carried out in seven passes. No descaling is applied during the rolling process. By reasonably setting the reduction rate of each pass, the thickness of the intermediate billet obtained in the rough rolling is 30mm~32mm. During the rolling process, the side guide allowance of the rough rolling 4th-7th passes is further reduced by 15mm-25mm, as shown in Table 7 below.
[0046] Table 7
[0047] (6) Hot rolling box: After the intermediate billet is rolled by rough rolling, the hot rolling box is used. The gap of the bending rolls in the hot rolling box is increased by 5mm. The tail value is corrected to the 4-5 o'clock position, as shown in Table 8 below.
[0048] Table 8
[0049] (7) Finishing: The intermediate billet is rolled in the finishing mill. The F7 process lubrication is removed during the rolling process. The L2 (secondary control system) optimizes the F5 reduction rate range to 21%-23%, the F6 reduction rate range to 15%-17%, and the F7 reduction rate range to 10%-13%. The operator adjusts the F5 roll between 130mm-145mm and the F6 roll between 120mm-135mm to control the micro-wave. F6-F7 can be rolled by steel pulling. The threading speed is appropriately increased by 0.5%, and the tensions between the F1 and F7 stands are 8MPa, 12MPa, 14MPa, 16MPa, 18MPa, and 20MPa, respectively, as shown in Table 9 below.
[0050] Table 9
[0051] (8) Laminar flow cooling: Laminar flow cooling adopts front-end cooling. No cooling water is used in the first 30 meters of the strip. The coiling temperature is increased by 100℃ in the 30~80 meter section. The cooling section in the first 100 meters adopts a relatively fixed water spray control gain. As shown in Table 10 below.
[0052] Table 10
[0053] (9) Coiling: The lead rate of the finishing mill exit roller table speed increased from 6.58 m / s to 7.3 m / s, and the manual tension after coiling was reduced from 23 N / mm. 2 Mentioning 26N / mm 2 To prevent the strip from deviating further after being unrolled on the roller conveyor, the tension during F3 strip throwing is reduced from 26 N / mm. 2 Manually reduce to 23 N / mm 2 To avoid surface imprints caused by excessively fast tail-end steel throwing speed resulting in strip folding.
[0054] (10) The development of the pinch roll lifting function is to simultaneously meet the two conditions of the roll load connection and the auxiliary roll opening command signal after the strip head enters the coiler and establishes tension. The pinch roll lifts the roll gap to 3 times the current value. This avoids the pinch roll pressure from the strip waviness from increasing, which would cause the strip to break brittlely under stress.
[0055] The actual data of heating and rough rolling of the five steel pieces described in the experiment are shown in Table 11 below, and the actual data of finish rolling are shown in Table 12 below.
[0056] Table 11
[0057] Table 12 This invention improves the stability of thin-gauge iron-nickel-based alloy rolling, reduces the scrap rate of iron-nickel-based alloys, saves time, increases output, and reduces costs.
Claims
1. A hot rolling method for thin-gauge iron-nickel-based alloys, characterized in that, This includes comprehensive control planning, billet preparation, heating, rough rolling, hot coiling, finishing rolling, layer cooling, and coiling, specifically including the following: (1) The unit transition, head and tail billet arrangement principles and thickness transition steps in the comprehensive control plan arrangement; (2) Controlling the heating temperature and furnace temperature ensures the quality of the billets produced from the furnace; (3) The roughing rolling adopts 7 passes, and the side guide opening is automatically reduced by 15-25mm after the roughing rolling load relay is turned on for 1 second; (4) The hot roll box adopts the method of correcting and increasing the gap between the bending rolls and lowering the unwinding roll 1B to ensure stable and smooth unwinding production; (5) The reduction ratio distribution of F1-F7 mills was optimized in the finishing mill, the looper tension control was increased, the correction value of F5-F6 roll shifting was 120mm-145mm, and the strip threading speed was limited to 6.0-6.3m / s to ensure the stability of finishing mill rolling; (6) Optimize the laminar flow cooling method, and use a relatively fixed water spray to control the gain in the 100-meter cooling section at the head; (7) The lead rate of the finishing mill exit roller table speed was increased by 12%, and the specific control of coiling tension threading and steel throwing was optimized.
2. The hot rolling method for thin-gauge iron-nickel-based alloys according to claim 1, characterized in that, Before rolling the iron-nickel-based alloy, two chromium steels with thicknesses of 3.5 mm and 3.0 mm are used as a transition. The iron-nickel-based alloy is transitioned to the target thickness by adjusting the thickness of the first 2-3 pieces in a stepped manner, with the difference between adjacent thicknesses controlled within 0.35 mm. The third or fourth piece directly reaches the target thickness. The coiling temperature transition principle is to transition sequentially according to the target temperature +30℃, +20℃, and +10℃.
3. The hot rolling method for thin-gauge iron-nickel-based alloys according to claim 1, characterized in that, The billet loading temperature is ≥250℃, and the temperature measurement point is the midpoint of the width of the slab. The time from entering the warehouse to loading into the furnace shall not exceed 1 hour.
4. The hot rolling method for thin-gauge iron-nickel-based alloys according to claim 1, characterized in that, The heating control method is as follows: The specific temperatures of each heating section of the walking beam furnace are as follows: the preheating section temperature is 950±20℃, the first heating section temperature is 1130±20℃, and the second heating and soaking section temperatures are 1160±20℃; the target steel temperature is 1150±20℃; the total furnace dwell time is ≥200min, of which the preheating section time is 55-60min, the first heating section time is 50-55min, the second heating section time is 55-60min, and the soaking section time is 40-45min.
5. The hot rolling method for thin-gauge iron-nickel-based alloys according to claim 1, characterized in that, Rough rolling: After heating, the slab is subjected to one main descaling pass and then rough rolling. The rough rolling process consists of seven passes. The descaling at the inlet and outlet of the rough rolling mill is not used. The thickness of the intermediate slab is 30mm~32mm. The side guide allowance for the 4th to 7th passes of the rough rolling is 55mm, and then reduced by 15mm-25mm.
6. The hot rolling method for thin-gauge iron-nickel-based alloys according to claim 1, characterized in that, After the intermediate billet is rolled by roughing, a hot rolling box is used. When the hot rolling box is used to roll the bending roll gap, it is set to 32mm. On this basis, it is increased by 5mm. The tail value is corrected to the position of 4-5 o'clock. When there is a curling head at the uncoiling head, the height of roll 1B is reduced by 10mm.
7. The hot rolling method for thin-gauge iron-nickel-based alloys according to claim 1, characterized in that, The intermediate billet is rolled in the finishing mill. The finishing rolling process involves 7 finishing mills, which are designated as F1 to F7. Before rolling, slippage in F7 is prevented, and the process lubricant in F7 is removed. The reduction rate of F5 is between 21% and 23%, the reduction rate of F6 is between 15% and 17%, and the reduction rate of F7 is between 10% and 13%. The threading speed of F6-F7 is appropriately increased by 0.5% based on 6.0 m / s to ensure that the steel pulling control is achieved in F6-F7.
8. The hot rolling method for thin-gauge iron-nickel-based alloys according to claim 1, characterized in that, Laminar flow cooling adopts front-end cooling, with no cooling water used in the first 30m of the strip, and the cooling section after the first 30m uses relatively fixed water spray to control the gain.
9. The hot rolling method for thin-gauge iron-nickel-based alloys according to claim 1, characterized in that, Increase the lead rate of the finishing mill exit roller speed by 10-12%, and manually increase the tension by 10-13% after coiling to avoid the strip from deviating further after being uncoiled on the roller. When throwing the F3 strip, manually reduce the tension by 10-12% to avoid surface imprints caused by excessively fast throwing speed at the tail end.
10. The hot rolling method for thin-gauge iron-nickel-based alloys according to claim 1, characterized in that, The development of the pinch roll lifting function in the coiler is achieved when two conditions are met simultaneously: the roll load is turned on and the auxiliary roll opening command signal is received after the strip head enters the coiler and tension is established. The pinch roll lifts to three times the current roll gap value.