RU2301714C1 - Method for straightening end curvature of cold rolled large- and mean-diameter tubes of alloyed hard-to-form steels and alloys - Google Patents

Abstract

FIELD: rolled tube production, namely process for straightening end curvature of cold rolled large- and mean-diameter tubes.

SUBSTANCE: method comprises steps of rolling tubes on cone mandrel in cold rolling mill while front end of cone mandrel is spaced from outer guide by distance 850 - 900 mm and inner diameter of guide exceeds outer diameter of tube by 30 - 40 mm. Then tube is straightened in six-roll straightening machine. End curvature of tube is straightened by means of detachable cylindrical inserts mounted onto mandrel stem with possibility of rotation and translation motion relative to stem. Said inserts are fixed at end side of stem by means of washer and fastening screw. Length of cylindrical inserts is determined according to expression Lin = K x Dt, where Dt - outer diameter of tubes, mm; K = (1.5 - 3.0), coefficient having large values for rolling tubes with smaller diameters. Diameter of cylindrical inserts is determined according to expression Din = Din. t - Δ, where Din.t - inner diameter of tubes, mm; Δ = (0.5 - 1.0) - gap between inner diameter of tube and outer diameter of insert whose large values correspond to tubes with larger wall thickness, mm. Front end of insert is rounded by radius whose value is determined according to expression R = Ro - R fr , where Ro - radius of cylindrical insert, mm; R fr - radius of front end of mandrel, mm. Detachable cylindrical inserts are made of cast iron with spherical graphite; lubricant layer is applied onto said inserts before rolling each tube.

EFFECT: lowered factor of metal consumption, lowered (or completely eliminated) quantity of curvature scrap of tube end.

7 cl, 1 dwg, 1 tbl, 1 ex

Description

The invention relates to pipe rolling production, in particular to a method for straightening the end curvature of cold-rolled large and medium-diameter pipes from alloyed hardly deformable grades of steel and alloys, and can be used in the production of pipes at KhPT 250 and KhPT 450 mills.

Correction of pipe curvature on all types of tube rolling units is carried out on 6-roll straightening machines with hyperboloid rolls (F.A. Danilov, A.Z. Gleiberg and V.G. Balakin. "Hot rolling of pipes", Moscow, 1962, p.290 -291. V.Ya. Osadchy and others. "Technology and equipment of pipe production", Moscow, "Intermet engineering", 2001, p. 177-182).

The disadvantage of this method is that it does not allow you to edit the end curvature at a length less than the distance between the rolls.

The closest technical solution is the method of straightening the end curvature of cold-rolled pipes of large and medium diameters from alloyed hard-to-deform steel grades and alloys in the deformation zone of the KhPT 250 and KhPT 450 mills, including rolling the tubes on a conical mandrel in a cold rolling mill, the front end of which is located from the outer wiring at a distance of 850-900 mm, and the inner diameter of the wiring is greater than the outer diameter of the pipe by 30-40 mm (drawing No. 1-122685 "Working line of the mill ХПТ 450", ТИ 158 - Тр.ТБ5 - 18 - 2002 "Rolling pipes on the mills of KhPT 160, HPT 250 and HPT 450 ").

The disadvantage of this method is that the output wiring is located from the front end of the conical mandrel at a distance of 850-900 mm, its inner diameter is 30-40 mm larger than the outer diameter of the pipe, and it is not intended to correct curvature, but acts as a guiding tool for output the front end of the pipe from the mill to the output roller table. This method cannot ensure the curvature of any portion of the pipe 1 mm per 1 m of length and, moreover, cannot correct the end curvature of the pipes (GOST 9941-81 "Seamless cold and heat-deformed pipes from corrosion-resistant steel").

The aim of the proposed method is the production of cold-rolled pipes of large and medium diameters from alloyed and difficult to deform steel grades and alloys on pipe mills ХПТ 250 and ХПТ 450 with an end curvature that meets the requirements of GOST 9941, reducing or completely eliminating the trimming of pipe ends according to curvature and reducing the cost coefficient of expensive of metals and alloys during the redistribution, the conversion pipe billet is a cold-rolled pipe, and consequently, a reduction in the cost of cold-rolled pipes from these grades of steel and alloy .

The problem is achieved in that in the known method of editing the end curvature of cold-rolled pipes of large and medium diameters from alloyed hardly deformable grades of steel and alloys, including rolling pipes on a conical mandrel in a cold rolling mill, the front end of which is located from the outer wiring at a distance of 850-900 mm and the inner diameter of the wiring is larger than the outer diameter of the pipe by 30-40 mm, with subsequent straightening of the pipe curvature in a six-roll straightening machine, the straightening of the curvature is carried out by removable cylinders with indigenous inserts that are mounted on the mandrel shank and fixed from the end of the shank by a washer and a fixing screw, removable cylindrical inserts are planted with rotational and translational motion relative to the shank, the length of the cylindrical inserts is determined from the expression

Lв = К · Dт,

where Dt is the outer diameter of the pipes, mm;

K = 1.5-3.0 - coefficient, large values of which relate to pipes of smaller diameter,

the diameter of the cylindrical inserts is determined from the expression

Dв = Dt int.-Δ,

where Dt ext. - inner diameter of pipes, mm;

Δ = 0.5-1.0 - the gap between the inner diameter of the pipe and the outer diameter of the insert, large values of which apply to pipes with a larger wall thickness, mm,

the front end of the insert is made along the radius, the value of which is determined from the expression

R = Ro-R.p.,

where Ro is the radius of the cylindrical insert, mm;

Rp.k - radius of the front end of the mandrel, mm,

removable cylindrical inserts are made of nodular cast iron, which is coated with a layer of lubricant before rolling each pipe.

The essence of the method lies in the fact that to solve this problem, straightening the end curvature of cold-rolled pipes of large and medium diameters from alloyed hardly deformable grades of steel and alloys, editing the end curvature is carried out in the center of deformation of the stands of the mills ХПТ 250 and ХПТ 450 with removable cylindrical inserts, which are mounted on the mandrel shank and is fixed from the end of the shank by a washer and a fixing screw. To give a degree of freedom, the landing of removable cylindrical inserts is carried out with the provision of their rotational and translational motion relative to the shank. To eliminate defects on the outer surface of the pipes in the form of scratches and scratches, the front end of the inserts is made in radius, and to reduce the coefficient of friction between the pipe and the inserts, the inserts are made of nodular cast iron and before rolling each pipe is additionally coated with a lubricant layer in the form of a mixture of machine oil, graphite and table salt. Since the trimming of the pipes along the end curvature does not exceed 600-700 mm, the length of the cylindrical inserts is determined in accordance with paragraph 3 of the claims, which, depending on the diameter of the rolled pipes, should be in the range of 600-700 mm. To obtain the end curvature of the pipes within GOST 9941 (not more than 1.0 mm per meter of length), the diameter of the cylindrical inserts is determined in accordance with paragraph 4 of the claims, which should be less than the inner diameter of the pipe by Δ = 0.5-1, 0 mm, large values of which apply to pipes with a larger wall thickness.

A comparative analysis of the proposed solution with the prototype shows that the claimed method for editing the end curvature of cold-rolled pipes of large and medium diameters from alloyed hardly deformable grades of steel and alloys differs from the known one in that the end curvature is made by removable cylindrical inserts that are mounted on the mandrel shank and fixed from the end the shank with a washer and a fixing screw, the landing of removable cylindrical inserts is carried out with the provision of rotational and translational motion relative to the shank, the length of the cylindrical inserts is determined from the expression Lв = К · Dt, where Dt is the outer diameter of the pipes, mm; K = 1.5-3.0 is a coefficient, large values of which relate to pipes of smaller diameter, the diameter of the cylindrical inserts is determined from the expression Dв = Dt int.-Δ, where Dt int. - inner diameter of pipes, mm; Δ = 0.5-1.0 - the gap between the inner diameter of the pipe and the outer diameter of the insert, large values of which relate to pipes with a larger wall thickness, mm, the front end of the insert is performed along the radius, the value of which is determined from the expression R = Ro-Rп .k., where Ro is the radius of the cylindrical insert, mm; Rp.k is the radius of the front end of the mandrel, mm, removable cylindrical inserts are made of nodular cast iron, which is coated with a lubricant layer before each tube is rolled. Thus, these differences allow us to conclude that the criterion of "inventive step" is met.

Comparison of the proposed method not only with the prototype, but also with other technical solutions in the art did not allow them to identify signs that distinguish the claimed method from the prototype, which corresponds to the patentability "inventive step".

Example

The method was carried out at the KhPT 450 pipe rolling mill of ChTPZ OJSC when rolling pipes 325 × 5 mm in size from VT1-0 titanium alloy. 40 conversion welded billets of 470 × 14 × 4000 mm in size made of VT1-0 titanium alloy were set into production, of which 20 were rolled into 325 × 5 mm pipes along the route 470 × 14 → 426 × 10 → 377 × 7 → 325 × 5 mm according to the existing technology, and 20 blanks according to the proposed method in accordance with the claims.

Data on rolling pipes 325 × 5 mm in size from VT1-0 titanium alloy at the KhPT 450 mill of ChTPZ OJSC according to the existing and proposed technologies are given in the table. The table shows that when rolling 20 pipes according to the existing technology, the cuts along the curvature of the ends amounted to 15.95 m: of these, the cuts of the front ends were 19 pipes, and the rear ends were 11 pipes. The average value of the trimmings was 0.53 m. Waste along the curvature was 0.367 kg. According to existing technology, 257.3 m or 5.918 tons of pipes were commissioned in accordance with GOST 22897-77. The expenditure coefficient of the VT1-0 alloy for this batch of pipes was 1.231. According to the proposed technology, there were no cuts along the curvature from the front ends of the pipes, and from the rear ends there were two pipes. Completed in accordance with GOST 22897 - 272.4 meters of pipes measuring 325 × 5 mm or 6.265 tons. The consumption coefficient of the alloy was 1.163. When rolling pipes using the proposed method for editing the end curvature of the pipes, a decrease in the expenditure coefficient of the expensive VT1-0 alloy 68 kg per each ton of pipes is obtained.

Table Data on rolling pipes 325 × 5 mm in size from VT1-0 titanium alloy at the KhPT 450 mill of ChTPZ OJSC according to the existing and proposed technologies Type of technology Assigned to the production of billets Rejected pipes by curvature Pipes handed over Consumption. coefficient metal Size (mm) PC. tons pcs (lane / rear) m t m t Creatures. 470 × 14 × 4000 twenty 7,281 19/11 15.95 0.367 257.3 5,918 1,231 Suggestion 470 × 14 × 4000 twenty 7,281 0/2 0 / 0.8 - 272.4 6,265 1,163

A diagram of the method for editing the end curvature of cold-rolled pipes of large and medium diameters from alloyed hardly deformable grades of steel and alloys at the KhPT 450 mill of OAO ChTPZ is shown in the drawing, where 1 is a conversion pipe; 2 - conical mandrel of the mill HPT; 3 - a cylindrical sleeve; 4 - mandrel shank; 5 - external output wiring; 6 - washer; 7 - cold rolled pipe; 8 - fixing screw.

The conversion pipe 1 was fed to the front table of the HPT 450 mill, into which the mandrel 2 was inserted, the front end of the mandrel 2 is made in the form of a shank 4 with a diameter of 200 ± 0.2 mm and a length of 650 ± 1.0 mm. A cylindrical insert with an outer diameter of 314.5 ± 0.1 mm was put on the shank of the mandrel, which corresponds to paragraph 3 of the claims, namely Db = Dt ext.-Δ or 325-2S-Δ = 325-10-0.5 = 314 5 mm, the length of which is 3.0 mm shorter than the shank (Lв = К · Dт = 647 mm). The inner diameter of the cylindrical sleeve was made with a sliding fit, i.e. the cylindrical sleeve had two degrees of freedom (rotational and translational). A cylindrical insert was fixed from the end of the shank with a washer 6 and a fixing screw 8, which was screwed along the axis of the shank to a depth of 10-15 mm. The front end of the cylindrical insert, in the course of rolling, was made along the radius, the value of which was determined from the expression R = Ro-Rp.k., which corresponded to paragraph 4 of the claims. The cylindrical insert was made of nodular iron castings. After rolling each pipe, a lubricant from a mixture of machine oil, graphite and sodium chloride was applied to the cylindrical sleeve and its mating parts.

The essence of the method for editing the end curvature of cold-rolled pipes of large and medium diameters from alloyed hardly deformable grades of steel and alloys lies in the fact that the front end of the conversion pipe 1 is reduced to the mill axis by rolls (calibers) in diameter, and then the wall of the conversion pipe S _{1 is} deformed to walls S ₂ with an extractor μ = (D ₁ -S ₁ ) S ₁ / (D ₂ -S ₂ ) S ₂ , where D ₁ is the outer diameter of the front pipe, mm, and D ₂ is the outer diameter of the cold-rolled pipe, mm. From pinch, the inner diameter of the cold-rolled pipe 7 is torn off from the mandrel and begins to bend due to uneven deformation along the gauge axis and outlets (especially when using single-seam welded pipes as conversion parts). The front end of the cold-rolled pipe is located on a cylindrical insert (sleeve) 3, which prevents its curvature, i.e. acts as an internal caliber, and then, as it rolls, it enters the external output wiring and the output rolling table of the HPT mill. A similar picture is observed when rolling the rear ends of pipes.

Using the proposed method for editing the end curvature of cold-rolled pipes of large and medium diameters from alloyed hard-to-deform steel grades and alloys at the KhPT 250 and KhPT 450 mills of ChTPZ OJSC will allow reducing or completely eliminating the trimming of the pipe ends along the curvature, reducing the metal consumption coefficient, and increasing the yield and consequently, reduce the cost of cold-rolled pipes from expensive grades of steel and alloys.

Claims (7)

1. The way to edit the end curvature of cold-rolled large and medium diameter pipes from alloyed hardly deformable grades of steel and alloys when rolling pipes in a cold rolling mill on a conical mandrel, the front end of which is located from the outer wiring at a distance of 850-900 mm, and the inner diameter of the wiring is larger than the outer pipe diameter of 30-40 mm, with straightening of pipes after rolling in a six-roll straightening machine, characterized in that the rolling is carried out on a mandrel, on the shank of which removable inserts are mounted, are fixed from the end of the shank washer and retaining screw. 2. The method according to claim 1, characterized in that the landing of removable cylindrical inserts is made with the provision of rotational and translational motion relative to the shank. 3. The method according to claim 1, characterized in that the length of the cylindrical inserts is determined from the expression Lв = K · Dт, where Dt is the outer diameter of the pipes, mm; K = 1.5-3.0 - coefficient, large values of which relate to pipes of smaller diameter. 4. The method according to claim 1, characterized in that the diameter of the cylindrical inserts is determined from the expression Dв = Dt int-Δ, where Dt int - inner diameter of the pipe, mm; Δ = 0.5-1.0 - the gap between the inner diameter of the pipe and the outer diameter of the insert, large values of which apply to pipes with a larger wall thickness, mm 5. The method according to claim 1, characterized in that the front end of the insert is made along the radius, the value of which is determined from the expression R = Ro-Rp.k, where Ro is the radius of the cylindrical insert, mm; Rp.k is the radius of the front end of the mandrel, mm 6. The method according to claim 1, characterized in that the removable cylindrical inserts are made of nodular cast iron. 7. The method according to claim 1, characterized in that the removable cylindrical insert before rolling each pipe is covered with a layer of lubricant.