JP3429157B2 - Large diameter ring manufacturing method of austenitic stainless steel - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an austenitic stainless steel.
Manufacturing of seamless large diameter rings of stainless steel .

[0002]

2. Description of the Related Art A seamless steel pipe of high alloy such as austenitic stainless steel is extruded by a press machine of Eugene Segerne hot extrusion method and heat treated. To meet the demand for steel pipes with high dimensional accuracy, cold drawing, cold drawing, and other processes are applied, followed by heat treatment.

The large-diameter ring is produced by cutting the large-diameter steel pipe manufactured by these methods with a cutting machine such as a band saw and supplying it to the customer.

When shipped with hot working finish, 2000 to obtain a large diameter ring having an outer diameter of 145 mm or more.
It is necessary to have a press machine that exceeds t. 1250t,
The maximum manufacturable outer diameter of press machine of 2000t and 3100t is 70mm at 1250t and 1 at 2000t.
It is limited to 45 mm and 230 mm at 3100 t due to the hot deformation resistance and the pushing force determined by the extrusion ratio.

In order to obtain a steel pipe having a large diameter and high dimensional accuracy when shipped by cold working finish, a steel pipe having a diameter larger than a desired size is subjected to cold drawing or cold drawing accompanied by reduction in outer diameter and wall thickness. Manufactured by cold drawing. Therefore, the outer diameter is 145 mm
In order to obtain the above steel pipe, the existence of a large cold drawing machine is indispensable. Regarding cold drawing, the outer diameter is currently 1
There is no large facility of 45 mm or more.

[0006]

SUMMARY OF THE INVENTION In order to obtain a large-diameter steel pipe, a large press machine of more than 2000 t is required, and in order to obtain a steel pipe with high dimensional accuracy, a large-scale cold drawing machine is required. A large amount is required, and small-scale production is expensive.

It is an object of the present invention to obtain a large-diameter ring of austenitic stainless steel , which is suitable for low-cost, high-mix low-volume production, and a large-diameter ring produced by the production method.

[0008]

[Means for Solving the Problems] A required number of steel pipes made of austenitic stainless steel , which is a base material having an outer diameter of up to 145 mm extruded by a medium-sized press machine of 2000 t or less, are band-sawed or cut off to obtain a ring. After that, burrs caused by cutting and adhering to the ring are removed by shot blasting and expanded by cold rolling to form a large diameter ring.

Since the cold rolling is finished by expanding the pipe into a predetermined size, it is possible to manufacture various kinds of rings having different outer and inner diameters from the same base material. Another feature is that a groove or the like can be circumferentially formed on the outer diameter surface or the inner diameter surface by changing the shape of the main roll or mandrel which is the rolling tool of the cold rolling device.

By this processing, not only the austenitic stainless steel is hardened but also magnetized (that is, the magnetic permeability is increased). However, in this case,
It has the drawback that it cannot be turned because it is too hard when turning the final part . For austenitic stainless steel is found, the general corrosion resistance becomes poor remains cold rolling,
It also has a drawback that stress corrosion easily occurs.

Work-hardening is performed by this cold rolling,
By subjecting the ring having magnetism to solution heat treatment , the hardness is made to facilitate cutting, and excellent corrosion resistance is obtained.

Further, sizing is performed by a sizing press in order to improve the outer diameter dimension and roundness which are distorted by the solution heat treatment . Then, shot blasting or pickling is performed for the purpose of removing scale by solution heat treatment .

Regarding the dimensional accuracy, the outer diameter dimensional accuracy is ± 0.2.
.About.0.3 mm, inner diameter dimension accuracy of ± 0.4 to 0.9 mm, and width dimension accuracy of ± 0.3 to 0.5 mm.
Generally, in the case of cutting a steel pipe having an outer diameter dimension of 145 mm or more as it is extruded, the outer diameter dimension tolerance is ± 0.9 mm or more and the inner diameter dimension tolerance is ± 1.0 mm or more, and the accuracy is very high. Here, the cold rolling apparatus will be briefly described.
As shown in FIG. 1 (a), the cold rolling device has a mandrel 1 having a circumferential groove 2 which matches a predetermined ring width, a receiving roll 3 which is in circumferential contact with the mandrel and allows the mandrel to rotate axially. The main roll 4 has a circumferential groove 5 matching the ring width and rotates about an axis parallel to the rotation axis of the receiving roll 3. Then, as shown in FIG. 1B, the mandrel 1 is inserted into the material 6 so that it comes into contact with the inner surface of the material 6, and the main roll 4 is rotated and pressed against the outer peripheral surface of the material 6. In this way, as shown in FIG. 1 (b), the axial rotation and pressing action of the mandrel 1 and the main roll 4 reduce the wall thickness of the ring-shaped portion, and as a result, the entire diameter is expanded. As shown in FIG. 1C, when the diameter of the expanded material 6 hits the outer surface of the material 6 whose diameter has been expanded, the proximity switch 8 installed in association with the sizer 7 is advanced. Is activated, the main roll 4 retracts and its pressing action stops. In this way a given ring is obtained.

Next, the sizing device will be briefly described. The sizing apparatus comprises a sizing punch 9 and a sizing case 10 as shown in FIG. After the material 11 is fed between the sizing punch 9 and the sizing case 10, the material 11 is inserted inside the sizing case 10 which is fixed by the sizing punch 9 which operates linearly. The sizing case 10 includes a sizing portion 12 having an inclination angle, a bearing portion 13 which is a parallel portion, and a relief portion 14 which is a portion to be discharged.
Therefore, the outer diameter of the material 11 is reduced as it is inserted, and the desired outer diameter of the ring is obtained by the bearing portion 13. The size of the bearing portion 13 is about 0.3 mm to 0.
Although it is reduced by about 5 mm, this is determined in consideration of spring back (elastic deformation).

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION C: 0.08% or less by weight,
Si: 1.00% or less, Mn: 2.00% or less, P:
0.040% or less, S: 0.030% or less, Ni: 8.
0.00-11.00%, Cr: 18.00-20.00%
In SUS304, which is a representative steel type of austenitic stainless steels including, a steel pipe extruded by a 2000t medium-sized press machine is cut with a band saw or a cut-off to form a ring. After removing cutting burrs from this ring by shot blasting, cold rolling is performed at a pipe expansion ratio of 1.2 to 1.8. Then, after heating to 1070 ° C., rapid solid solution heat treatment is performed to adjust the circularity and outer diameter dimension by sizing, and then shot blasting is performed to remove the scale by solution heat treatment to obtain a large diameter ring. .

[0016]

[Example] A steel tube having an outer diameter of 120 mm and an inner diameter of 95 mm was manufactured with a 2000t press using SUS304, which is a typical austenitic stainless steel, and was cut with a band saw to have a width of 29 mm, followed by shot blasting. The cutting burr was removed and used as the material. This material was cold rolled to an outside diameter expansion ratio of 1.1 to 1.45 defined by the formula shown below. Outer diameter expansion ratio = Outer diameter dimension after cold rolling / Outer diameter dimension of material Note that Table 1 shows the dimension after cold rolling.

[0017]

[Table 1]

Then, a solution heat treatment was carried out by quenching from a high temperature of 1070 ° C., and sizing was carried out.

Next, the difference in hardness and magnetic permeability of the ring obtained by cold rolling the material to a predetermined expansion ratio is shown in FIGS. 3 and 4, respectively. The hardness is measured by cutting the ring in the axial direction and measuring the cross section from the outer diameter surface to the inner diameter surface with a Vickers hardness measuring machine. The magnetic permeability is measured with a magnetic permeability measuring machine at the same position as the hardness measurement. The following measurements of hardness and permeability follow these. From this 1.14
It is confirmed that the tube has been hardened to 300 HV or more even at a pipe expansion ratio of a certain degree, and is magnetized due to the high magnetic permeability.

Next, the hardness and magnetic permeability after solution heat treatment are shown in FIG.
And FIG. 6 respectively. As a result, the hardness is stable at 200 HV or less, and the magnetic permeability is improved as much as the base material.

Next, the change in roundness before and after the solution heat treatment is shown in FIG. ST in the figure means solution heat treatment. The roundness also deteriorates in proportion to the increase in the pipe expansion ratio.

FIG. 8 shows the change in roundness due to sizing after solution heat treatment. This data is the change in circularity when the material is manufactured to have an outer diameter of 110 mm, an inner diameter of 90 mm, and a width of 90 mm, and a ring that has been cold worked at a pipe expansion ratio of 1.20 to 1.22 is sized. is there. Of course, the manufacturing method is the same as above. According to this data, the roundness was 0.27 mm to 1.53 mm after the heat treatment, but 0.04 mm to 0.
It has been improved to 12 mm.

Regarding the dimensional accuracy, the outer diameter dimensional accuracy ±
0.2 mm to 0.3 mm, inner diameter dimension accuracy ± 0.4 mm
0.5 mm, and width dimension accuracy is ± 0.3 mm to 0.5
mm is possible.

The hardness after sizing is 196 HV (187 HB equivalent) or less as shown in FIG.
47 and JIS C3214 Category C-1 are satisfied.

[0025]

As described above, the present invention is extruded by a medium-sized press machine without using a large-scale press machine or a large-scale cold drawing machine of more than 2000 tons, which is costly and difficult to produce in small lots and in various types. Outer diameter of 145 mm
As described above, a large-diameter ring with high dimensional accuracy can be obtained by expanding by cold rolling and molding, and is suitable for low-volume, multi-product production.

[Brief description of drawings]

FIG. 1 is a schematic view showing a cold rolling device, (a) shows a state in which a raw material is set in the device when viewed from above,
(B) shows the material in the state of being cold-rolled while viewed from above, and (c) shows the material at the end of cold rolling as viewed from the side.

FIG. 2 is a schematic view showing a sizing press device.

FIG. 3 is a graph showing hardness during cold rolling.

FIG. 4 is a graph showing changes in magnetic permeability during cold rolling.

FIG. 5 is a graph showing hardness during solution heat treatment.

FIG. 6 is a graph showing magnetic permeability during solution heat treatment.

FIG. 7 is a graph showing changes in circularity during cold rolling and solution heat treatment.

FIG. 8 is a graph showing changes in roundness during solution treatment.

FIG. 9 is a graph showing hardness during sizing.

[Explanation of symbols]

1 Mandrel 2 Mandrel circumferential groove 3 receiving roll 4 main rolls 5 Circumferential groove of main roll 6 material 7 sizer 8 proximity switch 9 Sizing punch 10 sizing cases 11 material 12 Sizing section 13 Bearing part 14 Runaway

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B21J 1/00-13/14 B21J 17/00-19/04 B21K 1/00-31/00 B21H 1 / 06 B21D 41/02

Claims (2)

(57) [Claims] In an austenitic stainless steel, a steel pipe extruded by a medium-sized press machine of 2000 t or less is used as a base material by cold rolling to form a groove in the outer or inner diameter surface in the circumferential direction. solid solution in the ring but to be molded
After heat treatment , sizing, and then shot blasting or pickling, JIS G3447
(Stainless steel sanitary pipe) and JIS G3214
(Stainless steel forged steel for pressure vessels) Category C-1 is satisfied, and a large-diameter ring having an outer diameter of 145 mm or more is obtained seamlessly with dimensional accuracy equivalent to that of cold drawing. Large diameter ring manufacturing method. 2. The JIS manufactured by the method of claim 1.
G3447 (Stainless Steel Sanitary Pipe) and JISG
3214 (Stainless steel forged steel for pressure vessels) Category C-
A large-diameter ring with an outer diameter of 145 mm or more that satisfies 1 and has a dimensional accuracy equivalent to that of cold drawing.