Rolling method for reducing high-temperature shearing bending ratio of 42CrMo

Abstract

The application discloses a rolling method for reducing high-temperature shearing bending ratio of 42CrMo, adopts 250mm*300mm*10500mm billets to produce φ30mm-80mm round steel; online configuration of heating furnace, high-pressure water descaling, 22 short stress line rolling mills of flat-stand alternation, 4 three-roller KOCKS rolling mills, 5 flying shear frames and 7 water tanks of online control cooling, adoption of heat preservation cover above the cooling bed and offline entry into the slow cooling room to realize slow cooling by covering heat preservation cloth; the high-temperature shearing bending ratio of 42CrMo round steel is reduced through low-temperature opening, control of water tank water pressure, adoption of heat preservation cover of the cooling bed, offline entry into the slow cooling room, etc. The application can effectively control the bending degree problem of 42CrMo type steel and improves the production efficiency and delivery rate.

Description

Technical Field

[0001] This invention relates to the field of rolling, and more particularly to a rolling method for reducing the high-temperature shear bending ratio of 42CrMo. Background Technology

[0002] Due to the high hardness of the 42CrMo series in the hot-rolled state, it is usually delivered by low-temperature sawing. After sawing, the ends have heavy melt edges and burrs, requiring chamfering before delivery. The sawing and segmenting machine has an output of about 120 tons / hour, which is relatively inefficient. High-temperature shearing can easily lead to uneven cooling and bending, requiring straightening before delivery and increasing process costs. Low-temperature shearing can easily cause end cracking, resulting in customer complaints and quality issues.

[0003] Therefore, it is necessary to develop new rolling methods to control the curvature problem of 42CrMo steel and improve production efficiency and delivery rate. Summary of the Invention

[0004] Purpose of the invention: To address the shortcomings and defects of existing technologies, this invention provides a rolling method for reducing the high-temperature shear bending ratio of 42CrMo steel. By employing methods such as low-temperature initial rolling, controlling the water pressure in the water tank, using an insulation cover on the cooling bed, and placing the steel in a slow cooling chamber after it leaves the production line, the bending problem of 42CrMo steel can be effectively controlled, thereby improving production efficiency and delivery rate.

[0005] Technical solution: The present invention provides a rolling method for reducing the high-temperature shear bending ratio of 42CrMo, characterized in that: a 250mm×300mm×10500mm billet is used for production. Round steel; online heating furnace, high-pressure water descaling, 22 alternating horizontal and vertical short stress line rolling mills, 4 three-roll KOCKS rolling mills, 5 flying shears and 7 online controlled cooling water tanks, the cooling bed is covered with an insulation cover and the line enters a slow cooling room, covered with insulation cloth to achieve slow cooling; by low temperature rolling, controlling the water pressure of the water tank, putting the cooling bed with an insulation cover, and entering the slow cooling room after the line, the high temperature shear bending ratio of 42CrMo is reduced.

[0006] The 42CrMo round steel and the heated steel are produced simultaneously.

[0007] The heating furnace provides uniform heating, with individual thermocouple temperature fluctuations ≤30℃.

[0008] During the rolling mill operation, water tanks #3 and #4 are used and the booster pumps are turned off. The pressure in water tanks #3 and #4 is maintained at 8 Bar. All water tanks #5, #6, and #7 are taken offline.

[0009] The aforementioned cooling bed is lowered in advance with an insulation cover, the length of which is 88m-95m, and the steel on the upper cooling bed is slowly cooled inside the insulation cover.

[0010] The 42CrMo round steel bars are produced in groups of two, with a 30-90 second interval between each group, and the shearing temperature is ≥420℃.

[0011] When the steel bars are placed in the slow-cooling room, they are stacked in a straight line. The length of the end of the fixed-length bundle is less than 0.5 meters when the steel bars are placed in the air at high temperature. Fixed-length and non-fixed-length steel bars are stacked separately to avoid bending caused by high temperature and pressure.

[0012] After stacking, the rolled material is covered with insulation cloth, and it can only be removed from the slow cooling room when the surface temperature of the rolled material is less than 100℃.

[0013] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The present invention solves the problem of... The problem of high-temperature shear bending in 42CrMo grade bars can be effectively controlled by adopting methods such as low-temperature initial rolling, controlling the water pressure in the water tank, using an insulation cover on the cooling bed, and placing the bars in a slow cooling room after they come off the production line. This improves production efficiency and delivery rate. Detailed Implementation

[0014] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0015] The rolling method of the present invention for reducing the high-temperature shear bending ratio of 42CrMo:

[0016] 1. CrMo steel is placed together with Group IV heated steel grades. If it is placed together with other steel grades, the difference between the target values ​​of uniformity and uniformity II is ≥30℃, and the empty step is ≥16 steps or the transition steel is ≥16 pieces. If the furnace head waits for ≥15 minutes for changing rolls or other reasons, the furnace head will retreat 3 steps before rolling.

[0017] 2. Heating process:

[0018]

[0019] 3. During production, use water tanks #3 and #4 and turn off the water tank booster pumps. Use water tank #5 to remove the steel from the production line. Ensure that the temperature of the steel entering the sizing and reducing process is uniform. Lower the insulation cover of the cooling bed in advance. Optimize the length of multiple lengths to ensure that all multiple lengths of steel on the cooling bed are slowly cooled inside the insulation cover.

[0020] 4. Control the production rhythm: steel is produced in groups of 2, with a 30-90 second interval between groups. If only 1 steel is left, then only 1 steel is produced in the last group. The cooling bed has 3 teeth and 1 movement. The cooling bed is manually pushed during the interval. The steel output rhythm is matched with the cold shear capacity. In principle, the cooling bed should be pulled out of the trolley without steel support as the standard. The connection between the front and back is stable, and the shearing temperature is ≥420℃.

[0021] 5. The output roller conveyor from the cooling bed is sent to the inspection table. Rolled materials should not be left to stand still. Non-standard lengths should be packaged separately. Flying shears should not be handled online. Two or three packages should be labeled on the weighing table. The overhead crane should be taken off the line as soon as possible to increase the temperature of the material entering the pit.

[0022] 6. After coming off the production line, place the material in a slow-cooling room for slow cooling. Pre-select a base warming pit with a similar length to the original dimensions, and stack them in a straight line. The length of the ends of the fixed-length bundles should be less than 0.5 meters above the ground after high-temperature production. Separate fixed-length and non-fixed-length bundles to avoid bending caused by high-temperature stacking. Choose a low, sheltered location. The height of the slow-cooling material should not exceed the outer wall. Cover with insulation cloth to improve the slow-cooling effect.

[0023] The proportion of high-temperature shear curvature within 0.25% is over 99.00%. This process can save straightening costs, improve CrMo steel production efficiency and yield, and shorten delivery time.

Claims

1. A rolling method for reducing the high-temperature shear bending ratio of 42CrMo, characterized in that: Using 250mm×300mm×10500mm billets, φ30mm-80mm round steel is produced. The system includes an online heating furnace, high-pressure water descaling, 22 alternating horizontal and vertical short-stress line rolling mills, 4 three-roll KOCKS mills, 5 flying shears, and 7 online-controlled cooling water tanks. An insulation cover is used above the cooling bed, and a slow-cooling chamber is constructed after the steel is rolled, covered with insulation cloth for slow cooling. By using low-temperature initial rolling, controlling the water tank pressure, using an insulation cover on the cooling bed, and placing the steel in the slow-cooling chamber after rolling, the high-temperature shear bending ratio of 42CrMo round steel is reduced. The heating furnace provides uniform heating, with individual thermocouple temperature fluctuations ≤30℃. The rolling mills use No. 3 and No. 4 mills during rolling. # Water tank # and water tank booster pump are turned off. The pressure of water tanks #3 and #4 is maintained at 8 Bar. All water tanks #5, #6, and #7 are taken offline. The insulation cover of the cooling bed is lowered in advance. The length of the steel is 88m-95m. The steel on the cooling bed is slowly cooled inside the insulation cover. Two 42CrMo round bars are produced in each group. The next group is produced after a 30s-90s interval. The shearing temperature is ≥420℃. When entering the slow cooling room, the round bars are stacked in a "I" shape. The length of the end of the fixed-length bundle after high-temperature production is <0.5m. Fixed-length and non-fixed-length bars are stacked separately to avoid bending caused by high-temperature pressing. After stacking, the steel is covered with insulation cloth. The surface temperature of the rolled material is <100℃ before it can be taken out of the slow cooling room.

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