Summary of teaching materials for rolling adjustment training

　　Adjustment of roll gap

　　Whether the roll gap adjustment is correct or not directly affects the stability of the rolling process, and also determines the size of the rolled piece outlet. The judgment basis of roll gap adjustment quality is: the rolling process is stable, the rolled piece size is qualified, the rolled piece shape is normal and the reduction is evenly distributed.

　　There are three specific operations:

　　① Roll gap adjustment (compensation adjustment) to compensate the wear of rolling groove after rolling a certain amount.

　　② The roll gap shall be flexibly adjusted according to the change of rolled piece size and rolled steel or process parameters.

　　③ Axial adjustment (roll staggering and roll shifting).

　　Tension setting and adjustment

　　The tension affects the size of the rolled piece. Requirements for it: the tension of each stand shall be constant to reduce the impact of tension fluctuation on the rolled piece size and rolling process.

　　There are three inspection methods:

　　① Knock the rolled piece with iron bar and other tools, and check the tension between the two racks to judge its size

　　② Observe the width of the UN rolled parts on both sides of the rolled piece to judge its size (the greater the width change, the greater the tension).

　　③ It can also be judged by the change of motor load current.

　　The tension adjustment is mainly realized by adjusting the rolling mill speed. However, before this process is realized, the height and dimension of rolled pieces of each rolling mill must meet the process requirements. Do not adjust the roll gap while adjusting the speed, which is easy to cause confusion.

　　Rules for shape adjustment of finishing mill

　　I. It is not allowed to adjust the 20 \27\\. After adjustment, the micro tension between frames will be damaged, resulting in dimensional accuracy fluctuation, which is easy to cause steel stacking accidents.

　　II. When the size of the finished product is unstable, the guide shall be checked. When the height is large and the width is large, adjust 19\base note 28\.

　　III. when the size of the finished product fluctuates greatly, the material type of each Sorty shall be checked (mainly the lead test bar).

　　IV. check the material type of pre finishing rolling.

　　Analysis and treatment of common accidents in rough and medium rolling

　　Head steel stacking:

　　① The rolling speed and roll diameter are set incorrectly. (correctly set the rolling speed, roll diameter and tension).

　　② Because the size of the upper shelf does not meet the requirements (too wide or too high), it is stuck in the guide. (the treatment measure is to frequently observe the material shape, and the method of adjusting the roll gap is "quadratic ellipse and primary circle").

　　③ The raw material is cracked or mixed, the steel temperature is too low, it is difficult to bite, and there are foreign matters in the guide. (the treatment measure is to check carefully before passing the steel).

　　④ Steel pouring caused by damaged guide, steel sticking and too large or too small guide opening on the shelf. (change the guide timely or in advance).

　　⑤ Elbows caused by incorrect rolling line on the shelf and deviation of guide assembly. (the treatment measures are to watch the guide frequently, observe the material type frequently and measure the size frequently).

　　Intermediate reactor steel:

　　① Bad material type causes tension difference and breaks rolled piece. (the treatment method is to adjust the material type and control the tension).

　　② Broken material or cleavage.

　　③ Mill speed drop. (the treatment measure is to find out the cause of the electrical system).

　　④ Roll break.

　　⑤ Slipping. (the treatment measure is to regrind the rolling groove). Improper clamping plate at rough rolling outlet, shape control, height of guide beam (warping head and binding head)

　　Analysis and treatment of common accidents in pre finishing rolling

　　Head steel stacking:

　　① The rolling speed and roll diameter are set incorrectly (the rolling speed, roll diameter and tension are set correctly).

　　② Because the size of the upper shelf does not meet the requirements (too wide or too high), it is stuck in the inlet guide (the treatment measure is to measure the material type, the roll gap is often adjusted, and the adjustment method is "quadratic ellipse and primary circle").

　　③ There are foreign matters in the cleavage, inclusion or guide (the treatment measure is to check the raw materials and guide before passing the steel).

　　④ The looper is not dropped or the looper is removed too early (the treatment measure is to find out whether the electrical delay is appropriate).

　　⑤ The large opening of the guide guard causes steel pouring or guide guard damage (the treatment measures are "frequently watching the guide guard, frequently observing the material type and frequently measuring the size").

　　Intermediate reactor steel:

　　① The tension of rough and medium rolling is too large and the rolled piece is broken due to tail swing (adjust the material type and control the tension).

　　② The guide is broken, steel is stuck and iron sheet is scraped (the treatment measure is to replace the guide in time or in advance).

　　③ Automatic shutdown in case of lubrication system failure (the treatment measure is to check the lubrication system).

　　④ The looper automatically falls into the looper (the treatment measure is to find out the electrical cause).

　　⑤ Automatic speed increase or speed decrease of rolling mill.

　　Analysis and treatment of common accidents in finish rolling

　　8 looper stacking steel:

　　① Head collision caused by incorrect rolling line and looper not falling in place (the treatment measure is to adjust the rolling line).

　　② The looper is pulled out too early, delayed or fails to pull out (the treatment measures are to check whether the water mist is large before the thermal inspection signal, whether it is blocked or whether the electrical fault signal flashes).

　　③ The looper is stuck but not removed (handle the ferrule caused by machinery).

　　④ 3. The cutting edge of the shear is seriously worn, and the elbow is cut (the treatment measure is to replace the cutting edge in time or in advance).

　　⑤ The cutting head is too short and is stuck in the guide groove after being brought in (lengthening the cutting head length).

　　3\

　　① The cutting head (tail) is too long and stuck in the guide groove.

　　② The cutting edge and rotation are worn and deformed.

　　③ The reverse wear position is incorrect. ④ Split of rolled piece.

　　Finishing mill intermediate stack steel:

　　① The shape and size of the material are inappropriate.

　　② The inlet guide is damaged (steel sticking, bearing damage, scraping iron sheet).

　　③ The inlet and outlet guides are loose.

　　④ Split of rolled piece.

　　⑤ Steel pouring caused by large guide opening.

　　Scrap box steel stacking:

　　① Piling up steel without threading (caused by poor installation of pinch roll, incorrect roll gap, incorrect installation of inlet and outlet guides, etc.)

　　② Several rounds of steel stacking during threading (caused by mismatching speed between finishing mill and pinch roll, improper installation of 28\\; inlet guide, premature opening of water in water cooling section, poor assembly of water cooling section, improper pressure of pinch roll, serious wear of guide cone sleeve at the inlet of threading machine, etc.)

　　measures:

　　① Carefully install pinch roll and inlet and outlet guide; Adjust the roll gap of pinch roll.

　　② Carefully install and check the 28\\\n inlet guide, water-cooling section guide, and the inlet guide cone sleeve of the threading machine; Set the matching speed of finishing mill and pinch roll; Clamping force of pinch roll; Adjust the length of the cooling water passing head of the opening water cooling section.

　　Roll ring burst:

　　① Poor pressurization causes roll shifting.

　　② The cooling water pipe is blocked.

　　③ The steel stacking treatment was not timely, and the water was boiled after the roll ring was burnt out.

　　④ The lubrication system is not heated well, and the roll shaft temperature is not enough. Install the cold roll ring.

　　⑤ Low temperature steel.

　　⑥ The material of the roll ring is poor or hard.

　　measures:

　　① When pressurizing, observe the pressure of the hydraulic trolley and keep it for 10 seconds after reaching the standard pressure.

　　② Check the cooling water pipe frequently.

　　③ Timely handle the steel stacking.

　　④ The roll ring can be installed only when the temperature of the roll shaft is close to 35 ℃.

　　⑤ Carefully check the roll ring quality.

　　⑥ Do not roll low-temperature steel.

　　Some common formulas for calculating rolling tables

　　Continuous rolling refers to rolling in which the rolled piece passes through each rolling mill in an equal volume per unit time.

　　Principle: continuous rolling constant C must be a constant,

　　Continuous rolling conditions: continuous rolling constant c=f1*v1= f2*v2= f3*v3= fn*vn

　　F - red billet area of rolled piece

　　V - speed of rolled piece

　　1. 2, 3... N stands for the first, second, third... N

　　Motor speed: n motor =n roll × I reduction ratio

　　Rolling linear speed: ν Line = π × D roll × N roll /60

　　ν Line - rolling speed, M / S;

　　D roll - working diameter of roll, mm;

　　N roll - roll revolutions per minute, rpm.

　　D roll = d roll original diameter -k factor

　　The adjustment range of the workshop: the maximum joint adjustment of the rolling mill motor is 10%, and the maximum joint adjustment of the looper is 3%.

　　Common finished product defects:

　　Crack: generally linear, occasionally curved, extending to the product surface longitudinally, horizontally or at a certain angle, with variable length. Causes: steel-making causes (micro cracks, subcutaneous bubbles, scabs and pits on the surface of steel billets, etc.); Reasons for steel rolling (unreasonable heating and rolling process, worn roll surface, excessively rough or scratched surface, scratched guide of rough rolling, improper operation, etc.). Will cause cracks on the product surface. Inspection method: for relatively large cracks, the manual torsion test method (small specification) is used for general cracks.

　　Folding: surface defects with linear or serrated thin lines on the surface along the rolling line direction and with corners on the cross section. It may be continuous or discontinuous, and it will be warped after torsion. Causes: shrinkage cavity, segregation, inclusion and other defects exist in the blank itself; If the pass is too full or not, and the guide opening is too large, the rolled piece swings back and forth to produce irregular ears, which will cause irregular folding; If the guide is not aligned or one guide wheel does not rotate, it will cause unilateral folding. Most folding due to guide defects occurs in the first few passes of the finished product. The reason for the intermittent folding of the finished product is that the material shape of the intermediate rolling and pre finishing rolling has problems (too large) or the opening of the inlet guide is too large. Carefully check the shape and size of each rack, the wear degree of rolling groove and the opening of guide, and observe whether there is steel pouring during rough and medium rolling.

　　Flower scratch: the scratch looks like a groove mark and is longitudinally distributed along the line. Cause: it is scratched by sharp objects (the rolled piece will be scratched by "sticking steel" on the guide, other sundries or poor processing, wear, fracture and burr of the guide, and there are other sundries or bumps in the guide groove and threading pipe of the water cooling section)

　　Scarring: there are appendages on the surface that can be removed, which are usually brought by raw materials, or caused by the meat falling off the front rolling groove or roll ring, as well as other small sundries brought in during rolling. If there are intermittent scabs, and the front rolling groove or roll ring loses meat, the surface of the rolling groove and roll ring shall be carefully inspected in such a case.

　　Roller print: it is concave and convex, usually appearing periodically, with variable shape and size. Cause: the roll ring or pinch roll is dented or damaged or the roll ring is cracked.

　　Pockmarked surface: the defect with sheet distribution composed of irregular thin concave convex points on the surface. The roll rings of the finished sorties or the sorties before the finished products are seriously worn.