Precision-rolling process

Details Precision-rolling process Precision-rolling process

2000-07-13

2001-04-17

Butler, Rodney A. (Department: 3725)

Metal deforming

By use of roller or roller-like tool-element

With cleaning or conditioning of tool, or lubrication of...

C072S226000, C072S227000, C072S250000, C072S225000

Reexamination Certificate

active

06216517

ABSTRACT:

The invention relates to a precision-rolling process for producing rolled stock in bar or wire form which is circular in cross section, while maintaining tight shape and size tolerances, and to a profile-rolling device for carrying out the process.
Currently, a plurality of systems for the precision-rolling (sizing) of rolling stock in bar form are known. The known systems are employed after continuous bar steel rolling mill trains or before or after wire blocks for the purpose of improving the dimensional accuracy of the rolling stock.
A known system comprises three two-high roll stands, in the order horizontal-vertical-horizontal. In this system, the round emerging from the continuous rolling mill train is deformed with the pass sequence oval-oval-round, with a low degree of deformation, to the desired final dimensions.
The drawbacks of this system are as follows: the oval cross sections are difficult to guide using the known rolling-stock guides. The rolling stock tends to become tilted, i.e. to twist in cross section, in particular if the distance between the stands is too great. Therefore, the rolling stock is not guided between the stands and the distance between the stands is selected to be as short as possible. This results in the further drawback that, in the event of disruption to the passage of rolling stock, the rolling stock which has become jammed can only be removed with difficulty. Maintenance of the stands is also complicated and laborious. A third drawback is the very complicated dimensional setting of the roll passes to the final dimensions, owing to the need to take into account the bearing clearances and the thermal expansion of the stands during operation.
A further system comprises two two-high stands, in the sequence vertical-horizontal, the second stand having preloaded rolls. In this case too, the round emerging from the continuous rolling mill train is deformed, with the pass sequence oval-round, to the desired final size. The preloaded rolls of the finishing stand compensate for the bearing clearances and the thermal expansion of the stand. In this case too, the major drawback of the difficulty of guiding the oval cross section into the round pass remains.
A third system comprises a rolling block with three rolling stands, in each of which three rolls are arranged at 120° to one another. The round emerging from the continuous rolling mill train is deformed, with the pass sequence trigonal-trigonal-round, to the desired final size. The drawbacks in this case are, firstly, the high mechanical outlay for driving and synchronizing the three rolls per stand, and, secondly, the fact that there is no compensation for the bearing clearances and thermal expansion of the stands.
The fourth known system comprises two roll frames, each with four rolls, of which in each case only a pair of rolls is driven, while the other pair is moved by the rolling stock. The roll axles of the second roll stand are arranged rotated through 45° with respect to the first. This system too has the drawback of the difficulty of presetting the roll passes, since the bearing clearances and thermal expansion have to be taken into account. Further drawbacks result from the position of the drive of the second stand, which is rotated through 45°, requiring a complicated mechanical drive. A further drawback is that the undriven pairs of rolls have to be accelerated to their working speed by the entry of the start of the rolling stock, which may result in damage to the base of the pass.
The invention aims to avoid these drawbacks and difficulties and is based on the object of providing a precision-rolling process for producing rolling stock in bar form or wire with a circular cross section, resulting in rolled stock with a particularly high level of accuracy and in a specific size while nevertheless—unlike in the prior art—providing ease of access to each of the roll stands, so that rolling can be continued again within a short period even in the event of disruption, i.e. so that the operating readiness of the installation can be restored as quickly as possible and simple maintenance is possible.
In a process of the type described in the introduction, this object is achieved by means of the combination of the following features:
rolling of the rolling stock in at least one two-high roll stand with an open pass, starting from any desired cross section, to form rolled stock which is polygonal, in particular tetragonal, in cross section,
guiding the rolled stock over a predetermined distance along one or more longitudinal edges and/or along those surfaces of the rolled stock which adjoin longitudinal edges, to a further roll stand, and
subsequent rolling to form rolled stock which is circular in cross section in at least one closed pass, in which rolling forces act on and deform the rolling stock in a star shape from at least three directions.
As a result of the bar steel being guided in order to be introduced into the further roll stand, which guidance is made possible by the polygonal cross section of the bar steel emerging from the two-high roll stand, it is possible to ensure that the feed of the bar steel into the further roll stand remains precisely constant along the entire length of the bar steel, so that both uniform deformation of the bar steel and, as a result, a uniform cross section can be achieved, and, owing to the uniform deformation, there is no tilting or the like even after the bar steel has emerged from the roll stand.
Preferably, the rolling stock is rolled in two two-high roll stands, which are arranged one behind the other, to form rolled stock which is tetragonal in cross section, and is guided between these two two-high roll stands.
A profile-rolling device for carrying out the process according to the invention is characterized by:
at least one two-high roll stand with an open, polygonal, in particular tetragonal, roll pass,
a rolled-stock guide which adjoins the two-high roll stand in the rolling direction and has guide devices which guide the rolled stock emerging from the two-high roll stand on one or more longitudinal edges and/or on the surfaces of the rolled stock which adjoin longitudinal edges of the rolled stock, and
at least one further roll stand with a closed, circular pass with at least three rolls arranged in a star shape.
A roll stand with a closed pass is known, for example, from DE-A-1,527,722. It has four discs, the working surfaces of which form a closed pass. Two opposite disc rolls are driven, whereas the other two disc rolls are moved by means of the material which is to be rolled. The disc rolls may be adjusted with respect to one another, so that the size of the pass can be varied. Each disc roll is acted on by another disc roll, displacement of the disc rolls in the radial direction of the other disc rolls enabling this change in the pass to take place. However, this means that the disc rolls can only be held together by relatively low forces, since it is impossible to apply any oppositely directed forces in order to prevent the disc rolls from becoming bent. Even without the additional action of forces which is brought about by the rolling, a closed pass of this nature is rather unsuitable for the long-term formation of a closed pass, and in fact there tends to be an undesirable change in size of the pass, so that the desired dimensioning of rolled stock cannot be achieved.
A particularly advantageous embodiment according to the invention is characterized in that two two-high roll stands with a tetragonal roll pass are provided with a guide arranged between them.
According to the invention, to make it easy to produce a pass which is always closed even under heavy rolling conditions, according to a preferred embodiment the rolls of the further roll stand are supported against one another by way of conical surfaces, the rolls being pressed against one another by a screw-down force which exceeds the rolling force by a preloading force.
A roll stand with a closed pass of the type described above is known per se, for example from EP-A-0,264,849.

Affiliated with

Also associated with

Rating

Precision-rolling process does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Precision-rolling process, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Precision-rolling process will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2525488