COMBINED RING ROLLING METHOD FOR SPHERICAL VALVE BODY

摘要

This invention relates to a combined ring rolling method for spherical valve body, which has the following procedures: 1) design for ring blank by computing ring blank volume and selecting reasonable rolling ratio according to the dimensions of forged ring; 2) design for rolling gap which includes the shapes and dimensions of working surfaces of main roll, mandrel and passive rolls according to the dimensions of ring blank and forged ring, the stable deformation condition of combined ring rolling and structure requirement of rolling equipment; 3) rolling forming with three stages of surface cross rolling, ring rolling and shaping by controlling of feeding speed of main roll and working positions of passive rolls. This invention has the technical economical advantages of low consumptions of energy and materials, high productivity and low production cost.

主权项

1. A combined ring rolling method for spherical valve body, comprising following steps:
1) design for ring blank
a ring blank section is designed to rectangular section, and its size can be designed as following steps: (1) determining ring blank volume
a forged ring volume V can be calculated as following equationV=πBRs2-πB312-πBr2, where Rs, B and r are respectively spherical radius, height and inner radius of the forged ring, and r is half value of the forged ring inner diameter d;
a oxidation loss coefficient α is 3%˜5%;the ring blank volume V0 can be designed as V0=(1+α)V; (2) determining rolling ratio
a rolling ratio k=s0/s, where s0 is section area of the ring blank and s is section area of the forged ring;the ring blank section area s0 can be calculated as s0=(R0−r0)B0, where R0, B0 and r0 are respectively outer radius, height and inner radius of the ring blank, and R0 is half value of the ring blank outer diameter D0, r0 is half value of the ring blank inner diameter d0;the forged ring section area s can be calculated ass=Rs2arcsinB2Rs-0.5BRs2-0.25B2+B(Rs2-0.25B2-r); a valve of k is 1.2˜3; (3) determining ring blank size the ring blank height B0=B; the ring blank inner radius r0 can be designed asr0=V02πks-ks2B0; the ring blank outer radius R0 can be designed asR0=V02πks+ks2B0; 2) rolling gap design
the combined ring rolling includes two stages, surface cross rolling and general ring rolling;during surface cross rolling stage, a rolling gap is made up of working surfaces of a main roll and two passive rolls;during general ring rolling stage, a rolling gap is made up of working surfaces of a main roll and a mandrel; (1) working surface of main roll
working surface of the main roll is adopted closed structure, and the main working surface is spherical surface;spherical radius of the main roll Rsm=Rs;working surface height of the main roll Bm=B+(1˜4) mm;linear velocity of the main roll vm is (1.0˜1.2) m/s;maximum working surface radius of the main roll can be determined asRm2=vm2πnm, where nm is rotational speed of the main roll, and it can be calculated by equationnm=nη, where n is rotational speed of motor, η is the transmission ratio;
minimum working surface radius of the main roll can be determined asRm1=Rm2-(Rsm-Rsm2-Bm24); there is a raised step respectively on upper and lower working surface of the main roll, which constitute a closed rolling gap;
radial length of the step should smaller than radial thickness of upper and lower surface of the forged ring, that isLmuaxial height of the step on main roll Bmu=Bml=(0.1˜0.3)B, where Bmu and Bml are respectively axial heights of the upper and lower step on the main roll; (2) working surface of mandrel
axial working surface height of a mandrel Bi=B+(20˜80) mm;working surface radius of the mandrel should satisfyRi≥Rm1(R0-r0)17.5βRm1-(R0-r0), where frictional angle β=arctan μ, μ is friction coefficient;
working surface radius of the mandrel should also satisfy Ri≦r0−10; (3) working surface of passive roll
spherical radius of a passive roll Rsc=Rs;working surface height of the passive roll Bc=Bm+(1˜4) mm;minimum working surface radius of the passive roll Rc1=(0.3˜0.7) Rm1;radial length of upper step Lcu and lower step Lcl on the passive roll can be determined by Lcu=Lcl=(1.5˜3) Lmu;axial height of upper step Bcu and lower step Bcl on the passive roll can be determined by Bcu=Bcl=(0.1˜0.3)B;two passive rolls are respectively arranged on the left and right sides below the mandrel;θ1 is the angel between the vertical and the line of the center points of left passive roll to the mandrel, and θ2 is the angel between the vertical and the line of the center points of right passive roll to the mandrel; valves of θ1 and θ2 are in the range of 50°˜70°;
during surface cross rolling stage, the two passive rolls are symmetrically arranged on the left and right sides of the mandrel, θ1 and θ2 are both about 60°;during general ring rolling stage, the arranged angel of the right passive roll θ2 is slightly larger than the left passive roll θ1, θ2 is about 65°˜70°, and θ1 is 50°˜55°; 3) rolling process
manufacture a ring blank and rolling gap according to the above design method, install the rolls in the rolling equipment, put the heated ring blank on the mandrel;rolling ring blank to forged ring should experience three stages of surface cross rolling, ring rolling and shaping;during rolling process, a operator should adjust position of the passive rolls and control feed speed of the main roll;in the first stage, adjust the passive rolls to the symmetrically arranged position, and make the ring blank into the rolling gap composed by the main roll and two passive rolls, control the main roll move downward with slow feed speed, which make the ring blank produce surface cross rolling deformation;in the second stage, when the ring surface profile completely fills the rolling gap, adjust the passive rolls to the asymmetrically arranged position, and make the ring blank into the rolling gap composed by the main roll and mandrel, control the main roll move downward with fast feed speed, which make the ring blank produce ring rolling deformation;in the third stage, when the ring out surface is close to contact the working surface of the left passive roll, control the main roll move downward with slower feed speed, precisely shaping the forged ring, while the ring out surface completely contacts the working surface of the left passive roll, stop downward feed motion of the main roll and move it upward, and the rolling process is over.