Method for improving rolling stability of steel for 700MPa-grade high-strength container
By optimizing the rolling process and parameter control, the rolling instability problem of 700MPa high-strength container steel was solved, improving production efficiency and yield, reducing the accident rate, and achieving efficient and low-cost production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANGANG STEEL CO LTD
- Filing Date
- 2026-03-10
- Publication Date
- 2026-05-12
AI Technical Summary
When rolling 700MPa high-strength steel for containers, there are rolling instability issues, which lead to frequent accidents such as strip deviation, head bending, tail swinging, and steel jamming, affecting production efficiency and product quality.
By optimizing the rolling process, controlling the time and temperature of the billet in the furnace, adjusting the rolling centerline, using looper and tension control, precisely controlling the mill load and temperature, adopting appropriate descaling methods and bending roll force, ensuring strip crown and shape, and combining hot rolling oil and speed mode control, stable rolling is achieved.
It improves the rolling stability and yield of 700MPa high-strength container steel, reduces the accident rate and processing time, increases the mill operation rate and production efficiency, and achieves low-cost and high-efficiency production.
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Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention belongs to the field of steel rolling technology, specifically relating to a method for improving the rolling stability of 700MPa high-strength container steel. Background Technology
[0002] 700Mpa grade high-strength container steel is mainly used to manufacture high-strength weather-resistant container bodies, lightweight container structural components, vehicle structural truck frames, trailer longitudinal beams, etc., which can achieve a weight reduction of more than 30%, improve load capacity and fuel economy, thereby reducing the weight of the container body and improving transportation efficiency.
[0003] The rolling of this steel grade is extremely difficult due to the large temperature fluctuations of the incoming material before finishing, the large side bending of the roughing stock, the irregular shape of the intermediate billet head and tail, and the uneven load distribution of the finishing mill. The rolling is unstable during finishing, and the occurrence of accidents such as strip deviation, head bending, tail throwing, and steel jamming increases, which reduces the rolling yield and affects the mill's operating rate. At the same time, it is also difficult to control the shape and accuracy of the strip, which causes great harm to production and product quality, and affects the smooth progress of production and contract delivery.
[0004] Therefore, improving the rolling stability of 700MPa high-strength container steel has become an important issue that urgently needs to be addressed. Summary of the Invention
[0005] Therefore, the purpose of this invention is to provide a method for improving the rolling stability of 700MPa high-strength container steel, which is easy to operate and adjust, and ensures smooth production.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] In a first aspect, the present invention provides a method for improving the rolling stability of 700MPa grade high-strength container steel, comprising the following steps: S1: Determine the total time the billet is in the furnace and the time the billet is in the soaking zone and the secondary heating zone according to the target thickness of the finished product and the billet charging temperature. The time the billet is in the soaking zone is controlled at 45min-60min. The temperature difference between the head and tail of the heating furnace is ≤20℃. The heating and tapping temperature is 1250℃-1260℃. S2: Adjust the rolling centerline in the roughing mill to ensure centered rolling, and adjust the tapping rhythm to avoid equal steel consumption; the roughing mill RT2 temperature is 1080℃-1120℃, and the temperature difference between the head and tail of the intermediate billet is ≤10℃; adjust the temperature to maintain consistent side bending of the intermediate billet in the transition material. S3: The finishing mill flying shear selects HMD mode, with a head shearing amount ≥230mm and a tail shearing amount ≥200mm; the looper is equipped with ILQ function; the final rolling temperature is 905℃-925℃; the descaling method is selected according to the target thickness of the finished product; the strip crown is 35μm-50μm; the bending roll force of the first three finishing mill stands is 80t-95t, and the bending roll force of the last four finishing mill stands is 40t-75t; the mill load is pre-adjusted in two stages, and the finishing mill load decreases sequentially from front to back, with the load difference between adjacent stands ≤500 tons.
[0008] During the process, placing steel is not allowed.
[0009] Among them, the looper input ILQ function performs closed-loop control of two variables: looper angle and tension.
[0010] Among them, F1-F5 are hot rolling oil from the first five stands of the finishing mill.
[0011] Among them, the looper input ILQ function controls the looper angle at the strip head at 22° and the tension is set incrementally.
[0012] Based on the above technical solution, further, in S1, determining the total furnace time of the billet and the time of the billet in the soaking zone and the secondary heating zone according to the target thickness of the finished product is specifically as follows: When the target thickness of the finished product is ≤2.0mm and the furnace loading temperature of the billet is >300℃, the time for the soaking zone and the second heating zone is 75min-90min, and the total time in the furnace is 195min-215min. When the target thickness of the finished product is ≤2.0mm and the furnace loading temperature of the billet is ≤300℃, the time for the soaking section and the second heating section is 80min-100min, and the total time in the furnace is 205min-225min; When the target thickness of the finished product is 2.0mm-3.0mm and the furnace loading temperature of the billet is >300℃, the soaking zone and the second heating zone time is 70min-90min, and the total furnace time is 190min-210min; When the target thickness of the finished product is 2.0mm-3.0mm, the furnace loading temperature of the billet is ≤300℃, the soaking zone and the second heating zone time is 75min-100min, and the total furnace time is 200min-220min.
[0013] The total time the billet spends in the furnace and the time it spends in the soaking zone and the secondary heating zone are determined based on the target thickness of the finished product, as shown in Table 1. In the table, the secondary heating zone plus the soaking zone refers to the total time spent in the soaking zone and the secondary heating zone.
[0014] Table 1: Total time in the furnace and time of the billet in the soaking zone and secondary heating zone.
[0015]
[0016] Based on the above technical solution, further, the adjustment of the rolling center line in S2 to ensure centered rolling specifically involves: before the centralized rolling of 700MPa grade high-strength container steel, a transition material is rolled first. The width difference between the transition material and the 700MPa grade high-strength container steel is controlled to be ≤40mm and the thickness difference to be ≤0.45mm. The rolling center line is adjusted using the transition material to ensure centered rolling; the number of transition materials is ≥10 pieces.
[0017] Among them, attention should be paid to the temperature difference between the beginning and end of the intermediate billet starting from the transition material, and adjustments should be made immediately if the difference is found to exceed the standard.
[0018] Based on the above technical solution, further, in step S3, selecting the descaling method according to the target thickness of the finished product specifically involves: When the target thickness of the finished product is ≤2.0mm, a single-row descaling method is adopted, and cooling water between the frames, roll gap water, and return spray water are not introduced before steel is fed in.
[0019] When the target thickness of the finished product is 2.0mm-3.0mm, a double-exhaust scale is adopted, and cooling water between the stands, roll gap water, and return spray water are not introduced before the steel is fed in.
[0020] Based on the above technical solution, further, when the final rolling temperature is >915℃, the next piece of steel is sequentially fed into the roll gap cooling water of the first and second finishing mills.
[0021] Based on the above technical solution, furthermore, the temperature is controlled by speed mode after the last stand of the rolling mill is threaded.
[0022] Based on the above technical solution, furthermore, the bending roll force is reduced from the first to the third finishing mill stand by stand.
[0023] Based on the above technical solution, the strip head further adopts micro-wave control.
[0024] Based on the above technical solution, the temperature of the roughing mill RT2 is further controlled by controlling the flow rate of the descaling cooling water.
[0025] Based on the above technical solution, the thickness of the intermediate billet is further controlled at 36-40mm.
[0026] The thickness of the intermediate billet is preferably 38 mm.
[0027] Compared with the prior art, the present invention has the following beneficial effects: This invention, through a series of effective technical measures such as process optimization, process parameter solidification, equipment precision improvement, temperature and intermediate billet thickness linkage control, tension solidification, and low-angle strip threading, significantly improves the stability and yield of rolling 700MPa high-strength container steel without increasing equipment costs. It solves the problems of strip misalignment causing head breakage and intermediate scrap jamming during rolling, reducing the accident rate and handling time, improving mill operating rate and rolling efficiency, achieving high-efficiency, low-cost, and large-scale production, and ensuring contract fulfillment rates. The invention's method is appropriate, the operation process is complete, the solutions are effective, and it is easy to master, operate, and implement. Detailed Implementation
[0028] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.
[0029] Example 1 The billet dimensions are 230×1240mm, and the rolled dimensions are 2.22×1220mm. Three heating furnaces are used, and the finishing mill has seven stands, designated F1, F2, F3, F4, F5, F6, and F7. To ensure that the 700MPa high-strength container steel is rolled under optimal conditions on the finishing mill, the billet rolling schedule is arranged for intermediate rolling. Before the final rolling, 14 transition steel pieces are rolled in a concentrated manner. The transition steel is SPHC hypoeutectoid steel, with finished dimensions of 10 pieces (2.65×1260mm) and 4 pieces (2.2×1255mm).
[0030] I. Heating System Control: 1. After the billet is loaded into the furnace, the total heating time of the cold material in the furnace is controlled at 210 min, with two heating elements and homogenization for 80 min and a total homogenization for 48 min. The billet exiting the furnace is then controlled at 1258℃. The total heating time of the hot material in the furnace is controlled at 195 min, with two heating elements and homogenization for 70 min and a total homogenization for 45 min. The billet exiting the furnace is then controlled at 1250℃.
[0031] 2. The temperature difference between furnaces and the temperature difference between the beginning and end of the heating furnace shall not exceed 20℃.
[0032] II. Roughing process control: 1. During rough rolling, it is not allowed to wait for the steel to roll or swing around; the thickness of the intermediate billet should be controlled at 38mm. 2. When rolling SPHC steel as a transition material, adjust the gap between the work rolls to prevent side bending when rolling 700MPa high-strength container steel, ensure a good material profile for finishing rolling, and ensure that the side bending trend of the three furnaces is consistent and the side bending difference is no more than 25mm.
[0033] 3. The temperature of roughing mill RT2 is controlled at 1080-1090℃. The flow rate of descaling cooling water in roughing mill is controlled to ensure that the temperature difference between the head and tail of intermediate billet does not exceed 10℃. The third descaling water is stopped in R2.
[0034] III. Finishing Rolling Process Control: 1. When using the flying shear, select HMD mode, with a head cutting amount ≥230mm and a tail cutting amount ≥200mm.
[0035] 2. The looper is put into ILQ function, the looper angle of the strip head is controlled at 22° and the tension is set incrementally.
[0036] 3. Before the intermediate billet enters the finishing mill, descaling water is applied using a double-stage descaling system to ensure the finishing mill's feed temperature. No interstand cooling water, roll gap water, or return spray water is used before the billet enters the mill. The strip exiting F7 is kept at a stable and uniform temperature, with the final rolling temperature controlled at 915±5℃. After the strip is threaded through the F7 mill, a speed-maintaining mode is used for temperature control. If the final rolling temperature is too high, the next strip is sequentially fed with roll gap cooling water from F1 and F2. Just before the strip is about to be ejected from the finishing mill, the roll gap cooling water from F2 and F1 is stopped sequentially from back to front to prevent tail-end accidents caused by excessively low strip tail temperatures. 4. To improve rolling stability, F1-F3 use large bending roll force to control strip crown, while F4-F7 focus on ensuring strip shape and straightness. Strip crown is controlled at 50μm, and wedge shape at 20μm. The bending roll force is set at 95t for F1, 91t for F2, 88t for F3, 74t for F4, 69t for F5, 64t for F6, and 50t for F7. Micro-wave control is used at the strip head.
[0037] 5. Hot rolling oil is used in F1-F5 mills, and the load of the finishing mill decreases sequentially from front to back. The load difference between adjacent stands does not exceed 500 tons, and the rolling force of F3-F7 shows a decreasing trend.
[0038] Example 2 The difference between this embodiment and embodiment 1 is that: The rolled 700MPa grade high-strength container steel has a specification of 1.922×1111mm. 22 transition plates are rolled in a centralized manner, and the finished product specifications after rolling are 2.65×1149mm and 2.22×1149mm, respectively.
[0039] I. Heating System Control: After the billet is loaded into the furnace, the total heating time of the cold material in the furnace is controlled at 215 minutes, with two heating elements and homogenization for 85 minutes and a final homogenization for 50 minutes. The billet exiting the furnace is then controlled at 1260℃. The total heating time of the hot material in the furnace is controlled at 200 minutes, with two heating elements and homogenization for 75 minutes and a final homogenization for 48 minutes. The billet exiting the furnace is then controlled at 1260℃.
[0040] II. Roughing process control: Ensure that the lateral bending trend of the three furnaces is consistent and the lateral bending difference is no more than 20mm.
[0041] The temperature of roughing mill RT2 is controlled at 1090-1100℃. The flow rate of descaling cooling water in roughing mill is controlled to ensure that the temperature difference between the head and tail of intermediate billet does not exceed 10℃. The third descaling water is stopped in both R1 and R2.
[0042] III. Finishing Rolling Process Control: When using the flying shear in HMD mode, the head cutting depth should be ≥260mm and the tail cutting depth should be ≥230mm.
[0043] Before the intermediate billet enters the finishing mill, descaling water is applied in a single-stage process to ensure the finishing mill's feed temperature. During the rolling mill, interstand cooling water, roll gap water, and return spray water are not introduced. The strip exiting F7 is kept at a stable and uniform temperature, and the final rolling temperature is controlled at 920℃. After the strip is threaded through the F7 mill, a speed-maintaining mode is used for temperature control.
[0044] To improve rolling stability, the strip crown is controlled at 35μm, and the wedge shape is smaller than the crown. The bending roll force is set to 90t for F1, 88t for F2, 81t for F3, 66t for F4, 64t for F5, 61t for F6, and 46t for F7. The set value and feedback value of the bending roll force are controlled within 10 tons.
[0045] Hot rolling oil is used in F1-F5 mills, and the load on the finishing mill decreases sequentially from front to back, with the load difference between adjacent stands not exceeding 300 tons. The rolling force of F3-F7 mills shows a decreasing trend.
[0046] Comparative Example 1 The difference between this comparative example and Example 1 is that: First, arrange for the centralized rolling of 8 transition steel pieces. The transition steel selected is SPHC hypoeutectoid steel, and the finished product specifications after rolling are 6 pieces of 2.75×1280mm and 2 pieces of 2.3×1260mm.
[0047] I. Heating System Control: After the billet is loaded into the furnace, the total heating time of the cold material in the furnace is controlled at 180 min, with two heating elements and homogenization for 70 min and 45 min respectively. The billet exiting the furnace is then controlled at 1258℃. The total heating time of the hot material in the furnace is controlled at 185 min, with two heating elements and homogenization for 65 min and 40 min respectively. The billet exiting the furnace is then controlled at 1230℃.
[0048] The temperature difference between furnaces and the temperature difference between the beginning and end of the heating furnace must not exceed 30℃.
[0049] II. Roughing process control: The thickness of the intermediate billet is controlled at 42mm; Ensure that the lateral bending trend of the three furnaces is consistent and the lateral bending difference is no more than 30mm.
[0050] The temperature of the roughing mill RT2 is controlled at 1040-1060℃. The flow rate of the descaling cooling water in the roughing mill is controlled to ensure that the temperature difference between the head and tail of the intermediate billet does not exceed 20℃.
[0051] III. Finishing Rolling Process Control: When using the flying shear, select CPG mode, with a head cutting depth of ≥300mm and a tail cutting depth of ≥260mm.
[0052] The looper is engaged with the CONV function, and the angle at which the strip head is threaded through the looper is controlled at 25° and the tension is set incrementally.
[0053] Before the intermediate slab enters the finishing mill, descaling water is applied using a double-stage descaling system to ensure the finishing mill's feed temperature. Before feed, water is introduced into the roll gaps of mills F1, F2, and F3, and return water is introduced into mills F6 and F7. The final rolling temperature is controlled at 900±10℃. After strip threading on mill F7, temperature control is achieved using a speed-maintaining mode. If the final rolling temperature is too high, the next strip is sequentially fed with cooling water between stands F1 and F2. Just before the strip is about to be ejected from the finishing mill, the cooling water between stands F1 and F2 is stopped to prevent tail-spinning accidents caused by excessively low strip tail temperatures. To improve rolling stability, F1-F3 use large bending roll force to control strip crown, while F4-F7 focus on ensuring strip shape and straightness. Strip crown is controlled at 55μm, and wedge shape at 30μm. The bending roll force is set at 98t for F1, 95t for F2, 92t for F3, 80t for F4, 73t for F5, 70t for F6, and 55t for F7. Micro-wave control is used at the strip head.
[0054] Hot rolling oil is used in F1-F5 mills, and the load on the finishing mill decreases sequentially from front to back, with the load difference between adjacent stands not exceeding 700 tons. The rolling force of F3-F7 mills shows a decreasing trend.
[0055] Comparative Example 2 The difference between this comparative example and Example 2 is that: The rolled 700MPa grade high-strength container steel has a specification of 1.922×1111mm. Sixteen transition plates are rolled in a centralized manner, and the finished product specifications are 11 plates of 2.75×1280mm and 5 plates of 2.3×1260mm.
[0056] I. Heating System Control: After the billet is loaded into the furnace, the total heating time of the cold material in the furnace is controlled at 190 min, with two heating elements and homogenization for 75 min and 46 min respectively. The billet exiting the furnace is then controlled at 1245℃. The total heating time of the hot material in the furnace is controlled at 185 min, with two heating elements and homogenization for 70 min and 43 min respectively. The billet exiting the furnace is then controlled at 1240℃.
[0057] II. Roughing process control: Ensure that the lateral bending trend of the three furnaces is consistent and the lateral bending difference is no more than 30mm.
[0058] The temperature of roughing mill RT2 is controlled at 1080-1100℃. The flow rate of descaling cooling water in roughing mill is controlled to ensure that the temperature difference between the head and tail of intermediate billet does not exceed 20℃. The third descaling water is stopped in R1.
[0059] III. Finishing Rolling Process Control: When using the flying shear, select CPG mode, with a head cutting depth of ≥350mm and a tail cutting depth of ≥300mm.
[0060] The looper is engaged with the CONV function, and the angle at which the strip head is threaded through the looper is controlled at 25° and the tension is set incrementally.
[0061] Before the intermediate billet enters the finishing mill, descaling water is applied using a double-stage descaling method to ensure the finishing mill's feed temperature. During rolling, F1, F2, and F3 roll gap water are introduced, and F7 return spray water is added. This ensures that the strip exiting F7 has a stable and uniform temperature. The final rolling temperature is controlled at 900 ± 10°C. After the strip is threaded through the F7 mill, a speed-maintaining mode is used for temperature control.
[0062] To improve rolling stability, the strip crown is controlled at 40μm, and the wedge shape is smaller than the crown. The bending roll force is set to 95t for F1, 90t for F2, 88t for F3, 74t for F4, 68t for F5, 64t for F6, and 55t for F7. The set value and feedback value of the bending roll force are controlled within 20 tons.
[0063] Hot rolling oil is used in F1-F5 mills, and the load on the finishing mill decreases sequentially from front to back, with the load difference between adjacent stands not exceeding 500 tons. The rolling force of F3-F7 mills shows a decreasing trend.
[0064] Example 3 The technical solutions of Example 1 and Comparative Example 1 were used to roll 700MPa high-strength container steel seven times. The technical solution of Example 1 had an accident rate of 0 and a yield of 98.7%. The technical solution of Comparative Example 1 had an accident rate of 45% and a yield of 85.6%.
[0065] It is evident that the technical solution of Example 1 has a lower accident rate and a higher yield than the technical solution of Comparative Example 1, highlighting the technical solution of the present invention. It improves the stability of rolling, increases the yield, reduces the occurrence of accidents, thereby reducing accident handling time and saving accident handling costs.
[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for improving the rolling stability of 700MPa high-strength container steel, characterized in that, Includes the following steps: S1: Determine the total time the billet is in the furnace and the time the billet is in the soaking zone and the secondary heating zone according to the target thickness of the finished product and the billet charging temperature. The time the billet is in the soaking zone is controlled at 45min-60min. The temperature difference between the head and tail of the heating furnace is ≤20℃. The heating and tapping temperature is 1250℃-1260℃. S2: Adjust the rolling centerline in the roughing mill to ensure centered rolling, and adjust the tapping rhythm to avoid equal steel consumption; the roughing mill RT2 temperature is 1080℃-1120℃, and the temperature difference between the head and tail of the intermediate billet is ≤10℃; adjust the temperature to maintain consistent side bending of the intermediate billet in the transition material. S3: The finishing mill flying shear selects HMD mode, with a head shearing amount ≥230mm and a tail shearing amount ≥200mm; the looper is equipped with ILQ function; the final rolling temperature is 905℃-925℃; the descaling method is selected according to the target thickness of the finished product; the strip crown is 35μm-50μm; the bending roll force of the first three finishing mill stands is 80t-95t, and the bending roll force of the last four finishing mill stands is 40t-75t; the mill load is pre-adjusted in two stages, and the finishing mill load decreases sequentially from front to back, with the load difference between adjacent stands ≤500 tons.
2. The method for improving the rolling stability of 700MPa high-strength container steel according to claim 1, characterized in that, In S1, the total furnace time of the billet and the time of the billet in the soaking zone and the secondary heating zone are determined according to the target thickness of the finished product as follows: When the target thickness of the finished product is ≤2.0mm and the furnace loading temperature of the billet is >300℃, the time for the soaking zone and the second heating zone is 75min-90min, and the total time in the furnace is 195min-215min. When the target thickness of the finished product is ≤2.0mm and the furnace loading temperature of the billet is ≤300℃, the time for the soaking section and the second heating section is 80min-100min, and the total time in the furnace is 205min-225min; When the target thickness of the finished product is 2.0mm-3.0mm and the furnace loading temperature of the billet is >300℃, the soaking zone and the second heating zone time is 70min-90min, and the total furnace time is 190min-210min; When the target thickness of the finished product is 2.0mm-3.0mm, the furnace loading temperature of the billet is ≤300℃, the soaking zone and the second heating zone time is 75min-100min, and the total furnace time is 200min-220min.
3. The method for improving the rolling stability of 700MPa high-strength container steel according to claim 1, characterized in that, The adjustment of the rolling centerline in S2 to ensure centered rolling specifically involves: before the centralized rolling of 700MPa grade high-strength container steel, a transition material is rolled first. The width difference between the transition material and the 700MPa grade high-strength container steel is controlled to be ≤40mm and the thickness difference to be ≤0.45mm. The rolling centerline is adjusted using the transition material to ensure centered rolling; the number of transition materials is ≥10 pieces.
4. The method for improving the rolling stability of 700MPa high-strength container steel according to claim 1, characterized in that, The specific steps for selecting the descaling method based on the target thickness of the finished product in S3 are as follows: When the target thickness of the finished product is ≤2.0mm, a single-row descaling method is adopted, and cooling water between the frames, roll gap water, and return spray water are not introduced before steel is fed in. When the target thickness of the finished product is 2.0mm-3.0mm, a double-exhaust scale is adopted, and cooling water between the stands, roll gap water, and return spray water are not introduced before the steel is fed in.
5. The method for improving the rolling stability of 700MPa high-strength container steel according to claim 4, characterized in that, When the final rolling temperature is >915℃, the next piece of steel is sequentially fed into the roll gap cooling water of the first and second finishing mills.
6. The method for improving the rolling stability of 700MPa high-strength container steel according to claim 1, characterized in that, Temperature control is performed using speed mode after the last rolling mill strip is threaded.
7. The method for improving the rolling stability of 700MPa high-strength container steel according to claim 1, characterized in that, The bending roll force is reduced progressively from the first to the third finishing mill.
8. The method for improving the rolling stability of 700MPa high-strength container steel according to claim 1, characterized in that, The strip head is controlled by micro-wave.
9. The method for improving the rolling stability of 700MPa high-strength container steel according to claim 1, characterized in that, The temperature of the roughing mill RT2 is controlled by controlling the flow rate of the descaling cooling water.
10. The method for improving the rolling stability of 700MPa high-strength container steel according to claim 1, characterized in that, The thickness of the intermediate billet is controlled at 36-40mm.