Centering method for seamless steel tube blanks

Centering method for seamless steel tube blanks

When hot-rolling seamless steel pipes, the centering of the tube blank is to ensure that the plug head accurately corresponds to the axis of the tube blank during perforation, and the center position of the tube blank section is along the axis of the tube blank. Process a round hole of a certain size into a funnel shape.

The reasons why seamless steel pipes require billet centering:

(1) It can improve the problem of uneven capillary head wall thickness. When the perforation is bitten once, due to the centering hole at the front end of the broken pipe, the front end of the tube blank will be deformed and the depression will increase. After rolling the pipe, the wall thickness is uneven and the ends are damaged.

(2) Increase the amount of pressure before plugging to improve the secondary bite of the tube blank. When perforating, the secondary bite is greatly affected by the centering and uncentering of the tube blank. Due to the centering of the tube blank, the horizontal projection length of the contact arc within the perforation cone increases. Centering actually increases the amount of compression in front of the plug and increases the contact area. Therefore, the drag friction of the roller on the tube blank increases, which is beneficial to Achieve secondary bite. When perforating alloy steel, since the amount of compression in front of the plug is not given at the top, it is more important to improve the secondary bite conditions through centering and reduce the uneven wall thickness at the front end of the capillary tube.

(3) Reduce wear on the plug nose and extend tool life. Centering can reduce the instantaneous impact force of the contact between the tube blank and the plug nose during the perforation process, increase the instantaneous contact area, and make the contact smooth. This reduces wear on the nose of the plug and increases plug life. For small diameter (<80mm) tube blanks and rolled thin-walled tubes (S<5mm), the centering method can be used to simplify the process. At this time, automatic centering can be achieved by forming a funnel-shaped cavity on the front end of the pipe due to surface deformation during cross rolling between two rollers.

Tube blank centering method

There are two ways to center pipes: cold centering and hot centering.

(1) Cold centering: Before heating the tube blank, drill holes on a special tube centering lathe. Or use oxygen-b rapid flame or arc method to burn holes. Cold centering is only used for stainless steel and high alloy steel, etc., and uses mechanical processing methods to make the position of the centering hole more accurate. The disadvantage is that the drill hole shape is improper during cold centering, which can easily cause centering inward folding defects.

(2) Heat centering: After the tube blank is heated, it is sent to the heat centering machine for punching, and then enters the punching machine for perforation. Thermal centering equipment is set up on the process line, and a pneumatic or hydraulic punch is used to center the front end of the broken pipe in a hot state. This method has high production efficiency and can realize automated operation. The metal is in a concentrated thermal state, the energy consumption is small, and there is no metal consumption. In addition, since the shape of the heat centering punch is easily adapted to the plug nose, a good centering hole shape can be obtained, which is helpful to avoid centering inward folding defects.

Article source: https://article-realm.com/article/Business/51768-Centering-method-for-seamless-steel-tube-blanks.html