JPS6240097B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the rotational speed of an axial roll in a ring rolling mill.

When manufacturing wheels, gears, and other annular products by rolling, as shown in FIG. Object R
Among them, a king roll K and a mandrel M are brought into rolling contact with the outer peripheral surface, and upper and lower axial rolls AX, AX are brought into rolling contact with both end faces in the axial direction. A method is adopted in which the annular product is rolled in the radial and axial directions to form an annular product having predetermined radial and axial dimensions. By the way, when such a Wagner mill is used to greatly reduce the radial thickness and axial height of a rolled object at the same time, the balance between the diameter elongation due to wall thickness reduction and the diameter elongation due to height reduction tends to be lost. The discrepancy between the rotational speed of the king roll K and mandrel M that contact the inner and outer circumferential surfaces of the rolled product and the rotational speed of the upper and lower axial rolls AX, AX that contact and press both end surfaces of the rolled material R in the axial direction. Due to this, the center of the rolled object shifts from the mill center, resulting in an unstable rolling condition with roll slippage, and especially when rolling a thin-walled annular product, the annular product may be distorted and not perfectly round. There was a problem.

For this reason, in the past, as shown in Figs.
A truncated cone-shaped upper and lower axle with an apex angle _θ so as to be able to roll into contact with both end faces in the axial direction of the rolled workpiece without crossing over, and whose circumferential speed varies depending on the driving rotation speed N K and the distance from the center. A rotation speed setting circuit was provided so that the drive rotation speeds of the rolls AX and _AX could be mutually adjusted based on the relationship between the drive rotation speed NAX and equation (1).

N _AX = D _K /D _AX・N _K …(1) However, D _K … King roll diameter (constant) D _AX … Axial roll diameter of the part facing the outer periphery of the rolled object The value of D _AX is (2 ) can be obtained using the formula.

D _AX = 2 (a + W _A ) sin θ/2 … (2) where a: Distance from the position corresponding to the apex to the tip of the axial roll assuming the axial roll is a cone θ: Vertex angle of the axial roll (Constant) W _A : Tracer roll position (distance from the tip of the axial roll to the part facing the outer periphery of the rolled object) and tracer roll position between the upper and lower axial rolls AX, AX to follow the outer periphery of the rolled object R. Based on the information regarding the tracer roll position W _A detected by the tracer roll T brought into rolling contact with this, from equation (2), the diameter D _AX of the axial roll AX and AX in the portion facing the outer peripheral edge of the rolled object is determined. At the same time, an axial controller obtains information on the rotation speed N _K of the king roll K detected by the tacho dynamo P ₁ and calculates the axial roll rotation speed N _AX according to the above equation (1) based on this information. The axial roll rotation speed N _AX (the same rotation speed for both axial rolls AX and AX) is set by the axial roll rotation speed setting device Q, and this axial roll rotation speed N _AX is sent to comparison circuits C ₁ and C ₂ . Axial rolls AX, which are input to the comparison circuits C ₁ and C ₂ , are detected by tachodynamometers P ₂ and P ₃ directly connected to the rotation shafts of the drive motors E ₁ and E ₂ of AX, respectively. roll
The actual rotation speeds of AX and AX are compared, and the drive motors E ₁ and E ₂ are controlled respectively so that the actual rotation speeds match the set rotation speeds. Theoretically, it is possible to set and control the rotation speed of the king roll K, that is, N _K , as is clear from equation (1), but in this case, both the axial rolls AX and AX are drive rolls. Compared to this, the king roll K is a drive roll, but the corresponding mandrel M is an idle roll. Therefore, controlling the rotation speed N _K of the king roll K changes the material speed at the inner and outer periphery of the rolled material R. Since the difference may vary and the curvature of the rolled object may change locally, no control is generally performed on the king roll K.

By the way, in the control method described above, the circumferential speeds of the king roll K and the axial rolls AX, AX are simply balanced, so for example, when the thickness reduction amount and the height reduction amount are small, the rolled The circumferential speed of the object approximately matches the circumferential speed of each roll, so
The rotational speed of the axial rolls can be controlled without any problem, but if the rolling reduction of both is large, the circumference of the rolled object will increase due to the thickness reduction in the radial direction, in other words, the diameter of the rolled object will increase. Because the elongation of the circumferential length of the rolled object due to height reduction in the axial direction, in other words, the elongation of the diameter of the rolled object, is greatly different, the material circumferential speed of the rolled object on the king roll side and the axial roll side are different. A large difference occurs between the circumferential speed of the material to be rolled and the material circumferential speed of the material to be rolled, and the control based on equation (1) cannot sufficiently compensate for this difference, causing the center of the material to be rolled O' to deviate from the mill center O (see Figure 4). ), rolling is performed under unstable conditions accompanied by roll slipping.

The present invention has been made in view of the above circumstances, and its purpose is to provide a process in which thickness reduction and height reduction of a workpiece to be rolled are performed at the same time. To provide a method for controlling the rotation speed of an axial roll in a ring rolling mill, which makes it possible to prevent distortion of an annular product by preventing the center from deviating from the mill center.

The method of the present invention is characterized by a ring rolling machine equipped with a king roll and a mandrel that roll down the ring-shaped rolled object in the radial direction, and a pair of upper and lower axial rolls that roll down the rolled object in the axial direction. A king roll and a mandrel that roll down the ring-shaped rolled object in the radial direction before and after the rolled object passes between the king roll and the mandrel, and a pair of upper and lower rollers that roll down the rolled object in the axial direction. In a ring rolling mill equipped with axial rolls, each wall thickness h _K , h′ _K in the radial direction before and after passing the rolled material between the king roll and the mandrel, and the thickness of the rolled material passing between both axial rolls. Each height h _AX in the axial direction before and after the object passes,
Based on h′ _AX , the distance W _A from the tip of the axial roll to the part facing the outer periphery of the rolled object, and the king roll rotation speed N _K , the material average circumferential speed of the rolled object on the king roll side, The rotational speed N of both the upper and lower axial rolls is adjusted so that the average peripheral speed of the material to be rolled on the axial roll side matches the material average circumferential speed of the rolled object.
The purpose is to set _AX using the following formula.

However, c: Width expansion coefficient D _K : King roll diameter D _AX = 2 (a + W _A ) sin θ/2 a: Distance from the position corresponding to the apex to the tip of the axial roll when the axial roll is assumed to be a cone θ : Apex angle of axial roll Hereinafter, the method for controlling the rotation speed of an axial roll in a ring rolling mill according to the present invention (hereinafter referred to as the method of the present invention) will be specifically explained based on drawings showing examples thereof. Figures 2 and 3 are explanatory diagrams of the method of the present invention, first of all, the average circumferential speed of the material to be rolled before and after passing between the king roll K and the mandrel M, and the relationship between the upper and lower axial rolls AX, AX. Looking at the average peripheral speed of the material before and after passing through the rolls, these can be considered to be similar to the average speed of the plate material before and after passing through the rolls in the case of plate rolling. Therefore, when calculating the average speed of the plate material in the case of plate rolling, the speed v of the plate material before passing through the rolls and the speed v' of the plate material after passing the rolls can be expressed as follows.

v=e ^El v′ v′=(1+ψ)V where V: Roll circumferential speed ψ: Advance ratio El: Elongation strain Therefore, the average speed of the plate material can be expressed by equation (3).

=(v+v')/2=(1+e ^El /2)(1+ψ
)V...(3) Therefore, in the case of a ring rolling mill, the average speed _K of the material to be rolled when passing between the king roll K and the mandrel M, and the rolling material passing between the upper and lower axial rolls AX, AX. Applying to the average speed _AX of the material, the condition that the center of the ring-shaped rolled material does not deviate from the mill center, that is, _K = _A
When _X is given, the rotation speed of axial roll AX, AX (both upper and lower axial rolls are the same) N _AX
is obtained from equation (4).

N _AX = (1+ψ _K /1+ψ _AX ) (1+e- ^ElK /
1+e− ^ElAX ) (D _K /D _AX )N _K …(4) However, ψ _K , ψ _AX : Advanced rate of king roll side and axial roll side El _K , El _AX : Advance rate of king roll side and axial roll side Elongational strain _K , _AX : Diameter of the king roll and axial roll facing the wall thickness centers of the king roll side and the axial roll side Here, in the case of ring rolling, the advance ratio ψ is as small as approximately 0.01, so 1+ψ _K /1+ψ _AX 〓It can be considered as 1. Furthermore, the roll diameters _K and _AX facing the center of wall thickness are respectively _K = d-s/dD _K ...(5) _AX = d-s/dD _AX ...(6) where d: Outer diameter of the rolled object s: Outer diameter of the rolled object Since there is a relationship between the wall thickness in the radial direction of the rolled product, D _K /D _AX = D _K /D _AX after all.

Therefore, formula (4) is simplified to N _AX 〓(1+e- ^ElK /1+e- ^ElAX )(D _{K
/DAX)NK...(4 '} ).

Here, the elongation strain El is generally calculated using the equation (7) using the width expansion coefficient c, that is, El = (1-c) l _o h/h'... (7) where h: rolling reduction of the rolled material before rolling. Height h′: Can be determined from the rolling height of the rolled object after rolling.

The width expansion coefficient c is, for example, the ratio of the width expansion strain E _w to the rolling strain E _h c=-E _w /E _h ...(7') However, E _w = l _o w'/w E _h = l _o h'/ h w, w': A well-known constant expressed as the wall thickness in the radial direction before and after rolling.

The width expansion coefficient c can be determined by measuring El, h, and h' by performing ring rolling experiments of the applicable size multiple times. A plurality of c's are obtained by substituting , and the average value is used.

Then, using the above equation (7), the equation (4′) finally becomes However, h _K , h' _K : Each thickness in the radial direction before and after rolling on the king roll side h _AX , h' _AX : Each height in the axial direction before and after rolling on the axial roll side. Therefore, the rotation speed setting circuit for axial rolls AX and AX is configured to satisfy this requirement. That is, in the method of the present invention, it is sufficient to set N _AX so as to satisfy the above equation (8).

In the above formula (8), is the elongation ratio in the circumferential direction of the rolled object in rolling by the king roll side and rolling by the axial roll side, and this is set as K ₁ , and D _K /D _AX is the elongation ratio in the circumferential direction of the rolled object in rolling by the king roll side and rolling by the axial roll side. , AX is the roll diameter ratio, so if we set this as K ₂ , equation (8) becomes N _A
X 〓K ₁ , K ₂ , N _K . In the embodiment of the method of the present invention, an optical width measuring instrument is used to obtain information on the radial wall thickness h _K of the workpiece R on the king roll side before rolling, which is necessary for calculating the above-mentioned _K1 . A potentiometer S ₁ is provided in the rolling direction of the mandrel M to obtain information on the radial wall thickness h′ _K after rolling on the king roll side, and a potentiometer S ₁ is provided in the rolling direction of the mandrel M. An optical width meter F ₂ is installed to obtain information on the axial height h _AX , and a potentiometer S ₂ is movable up and down to obtain information on the axial height h′ _AX after rolling. A tacho dynamo P ₁ is provided in the rolling direction of the upper axial roll _AX , which is configured as shown in _FIG . It is provided.

These optical width meters F ₁ , F ₂ , potentiometers S ₁ , S ₂ , tracer roll T and tacho dynamo
Based on the information input from P ₁ to the axial roll rotation speed setting device Q and the information on the king roll diameter D _K input as known information in advance, the axial rolls AX, AX are set according to formula (8). The rotation speed setting value _NAX is calculated and this calculated value is input to the comparator circuits _C1 and _C2 . Comparison circuits C ₁ and C ₂ include upper and lower axial rolls AX, and a tacho dynamo directly connected to AX.
Axial roll AX detected by P ₂ and P ₃ ,
The actual rotation speed of AX is input, and this is compared with the rotation speed setting value _NAX input from the axial roll rotation speed setting device Q, so that the actual rotation speed matches the rotation speed setting value _NAX . axial roll
Controls the drive motors E ₁ and E ₂ of AX and AX.

As described above, the method of the present invention uses a ring rolling mill equipped with a king roll and a mandrel that roll down a ring-shaped rolled object in the radial direction, and a pair of upper and lower axial rolls that roll down the rolled object in the axial direction. , each thickness in the radial direction before and after the object to be rolled passes between the king roll and the mandrel, each height in the axial direction before and after the object to be rolled passes between the two axial rolls, and the tip of the axial roll. Based on the distance of the axial roll from to the part facing the outer periphery of the rolled object and the rotation speed of the king roll, calculate the average peripheral speed of the material of the rolled object on the king roll side and the material of the rolled object on the axial roll side. Since the rotation speed of the axial roll is set based on equation (8) so that the average circumferential speed is the same, the center of the rolled object does not deviate from the center of the ring mill, and therefore the king roll, mandrel and So-called roll sliding between the upper and lower axial rolls and the rolled object is suppressed as much as possible,
The method of the present invention has excellent effects, such as the rolled product being accurately rolled into an annular product without distortion.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the rolling mode of a ring-shaped product; FIGS. 2 and 3 are a plan view and a sectional side view of a ring rolling mill for explaining the method of the present invention, respectively;
4 and 5 are a plan view and a sectional side view of a main part of a ring rolling mill for explaining the conventional method. K...King roll, M...Mandrel, AX...Axial roll.

Claims (1)

[Scope of Claims] 1. A ring rolling mill equipped with a king roll and a mandrel that roll down a ring-shaped rolled object in the radial direction, and a pair of upper and lower axial rolls that roll down the rolled object in the axial direction. Each thickness in the radial direction h _K , h′ _K before and after passing the rolled object between the king roll and the mandrel, and each height h in the axial direction before and after passing the rolled object between both axial rolls Based _{on AX} , h' _AX , the distance W _A from the tip of the axial roll to the part facing the outer periphery of the rolled object, and the king roll rotation speed N _K , the material average circumferential speed of the rolled object on the king roll side. and,
The rotational speed _NAX of both the upper and lower axial rolls is set according to the following formula so that the material average circumferential speed of the rolled object on the axial roll side matches the axial roll speed of the axial roll in a ring rolling mill. Rotation speed control method. However, c: Width expansion coefficient D _K : King roll diameter D _AX = 2 (a + W _A ) sin θ/2 a: Distance from the position corresponding to the apex to the tip of the axial roll when the axial roll is assumed to be a cone θ : Vertical angle of axial roll