RU2576718C1 - Rolling mill two-ply roll with axial cavity - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to pipe production. Claimed roll consists of outer chilled working ply and inner unchilled nonworking ply made of different composition iron alloys. Roll pass is made in said outer working ply. The latter is made of chilled iron. The latter contains the following elements in wt %: 2.9-3.8 C; 0.3-0.8 Mn; 0.4-1.0 Si; up to 0.16 S; up to 0.5 P; 0.6-1.2 Cr; 1.2-2.5 Ni. Note here that the content of Cr and Ni is defined from the ratio of components 1:(1.7-2.8). While inner nonworking play is made from gray cast iron its chemical composition not specified. Depth of said outer chilled working ply makes 40-55 mm at maximum radius of the groove not exceeding 35 mm.

EFFECT: higher hardness and wear resistance at regrinding and changeover to the pipe larger OD.

2 cl, 1 dwg, 1 tbl

Description

The invention relates to pipe production and can be used in the production of seamless hot-rolled pipes on reduction or calibration mills.

Known two-layer rolling rolls with an axial cavity of reduction and calibration mills, which are made of unalloyed cast iron SP-62, containing, by weight. %: 2.7-3.9 C; 0.2-0.8 Si; 0.2-0.6 Μn; up to 0.5 Ρ; to 0.12 S. The rolls are bleached. Rolls are made by casting billets into a stationary water-cooled chill mold. The depth of the obtained bleached layer ranges from 10 to 30 mm, the hardness is 62-72 Shore units (46-54 HRC). In addition to the bleached layer in the rolls, the transition and gray zones are distinguished, forming an internal unbleached non-working layer. The hardness of the rolls decreases from the bleached layer to not bleached. In the bleached layer, which is the worker, a caliber stream is made, the radius of which is determined by the outer diameter of the rolled pipe (G.I. Gulyaev et al. “Technology of continuous flawless rolling of pipes”, M., Metallurgy, 1975, p. 194). Known rolls do not have stable hardness and wear resistance due to insufficient depth and disordered and nonequilibrium microstructure of cast iron bleached layer, which does not ensure the preservation of hardness to the entire depth of the gauge stream when regrinding as it wears and when moving to a larger outer diameter of the pipe.

Closest to the proposed invention are two-layer rolls with an axial cavity, which have a working bleached layer of cast iron alloyed with 0.5-1.0% Cr and 2.0-3.0% Ni, and an inner non-working layer of gray cast iron, which get casting in a stationary water-cooled chill. The depth of the working bleached layer does not exceed 30 mm. In a bleached layer, a caliber stream is made, the radius of which is determined by the size of the rolled pipe (GI Gulyaev et al. “Technology of continuous flawless rolling of pipes”, M., Metallurgy, 1975, pp. 194-195). The rolls of the prototype also do not have stable hardness and wear resistance due to insufficient depth and disordered and nonequilibrium microstructure of cast iron of the working bleached layer, which does not ensure the preservation of hardness throughout the depth of the gauge stream when regrinding as it wears and when moving to a larger outer diameter of the pipe.

The objective of the invention is to remedy these disadvantages.

The technical result from the use of the invention consists in obtaining a two-layer roll of the rolling mill with an axial cavity, the working bleached layer of cast iron of which, at a depth of not less than the maximum radius of the gauge stream, has an ordered and equilibrium microstructure, which ensures hardness throughout the depth of the gauge stream during regrinding as it wears and when switching to a larger outer diameter of the pipe.

The technical result from the use of the invention is achieved in that in a two-layer roll of a rolling mill with an axial cavity, consisting of an external bleached working and internal unbleached inoperative layers made of cast iron alloys of different chemical compositions, in the outer bleached working layer of which is made a caliber stream, the outer bleached working the layer is made of wear-resistant cast iron, containing, by weight. %: 2.9-3.8 C; 0.3-0.8 Μn; 0.4-1.0 Si; up to 0.16 S; up to 0.5 P; 0.6-1.2 Cr; 1.2-2.5 Ni, in which the content of Cr and Ni is determined from the ratio of components 1: (1.7-2.8), and the internal unbleached non-working layer is made of gray cast iron, the chemical composition of which is not regulated, while the depth the outer bleached working layer is 40-55 mm with a maximum caliber radius of not more than 35 mm.

In FIG. 1 shows a cross section of a two-layer rolling roll with an axial cavity.

A two-layer rolling roll 1 with an axial cavity 2 consists of an external bleached working layer 3 and an internal unbleached non-working layer 4. The external bleached working layer 3 is made of wear-resistant cast iron containing, by weight. %: 2.9-3.8 C; 0.3-0.8 Μn; 0.4-1.0 Si; up to 0.16 S; up to 0.5 P; 0.6-1.2 Cr; 1.2-2.5 Ni with a layer depth not less than the maximum radius R of the stream of caliber 5, in which the content of Cr and Ni is determined from the ratio of components 1: (1.7-2.8). The depth of the outer bleached working layer is 40-55 mm with a maximum caliber radius of not more than 35 mm. The inner unbleached non-working layer 4 is made of gray cast iron MF, the chemical composition of which is not regulated. A two-layer rolling roll with an axial cavity is obtained after machining a cast hollow billet, including processing the outer and inner surfaces, cutting into parts and cutting a caliber stream in the outer working layer of each of the parts.

As a casting method of a workpiece, for example, a centrifugal casting method is used. When casting the workpiece, the first to pour wear-resistant cast iron containing, by weight. %: 2.9-3.8 C; 0.3-0.8 Μn; 0.4-1.0 Si; up to 0.16 S; up to 0.5 P; 0.6-1.2 Cr; 1.2-2.5 Ni with a layer depth not less than the maximum radius R of the stream of caliber 5, in which the content of Cr and Ni is determined from the ratio of components 1: (1.7-2.8). The inner unbleached non-working layer 4 is made of gray cast iron MF, the chemical composition of which is not regulated.

The choice of the interval of the content of components of wear-resistant cast iron is associated with favorable from the point of view of obtaining the required level of hardness, high depth of the bleached working layer, reducing the transition zone. It was experimentally obtained that the Cr and Ni content, determined from the ratio of components 1: (1.7-2.8), leads to a linear increase in the depth of the bleached working layer. The depth of the outer bleached working layer of 40-55 mm with a maximum gauge radius of not more than 35 mm ensures the preservation of hardness throughout the depth of the caliber stream during regrinding as it wears and when switching to a larger outer diameter of the pipe.

The implementation of the internal non-working layer of gray cast iron MF, the chemical composition of which is not regulated, allows to reduce the total consumption of metal, including alloying elements (nickel, chromium).

The technical solution was tested in an industrial environment. Wrought iron rolls of the proposed composition were made. The resulting rolls have:

- the maximum radius R of the stream of caliber is 35 mm;

- the hardness of the outer working layer at a depth of 15 mm is 43.5-51.5 HRC, at a depth of 45 mm - 41.0-51.5 HRC;

- the average resistance of the rolls of the reduction mill by one regrinding according to the proposed technical solution exceeds that of third-party rolls.

The effectiveness of the proposed technical solution is confirmed by testing the rolls of the TPA-80 reduction mill, manufactured according to the proposed solution in comparison with third-party rolls.

The test results are presented in table. one:

Claims (2)

1. A two-layer roll of a rolling mill with an axial cavity, in the outer working layer of which a gauge stream is made, while the outer working layer is made of bleached cast iron alloyed with chromium and nickel, and the inner non-working layer is made of gray cast iron, characterized in that the outer working layer made of wear-resistant cast iron, containing, by weight. %: 2.9-3.8 C; 0.3-0.8 Μn; 0.4-1.0 Si; up to 0.16 S; up to 0.5 P; 0.6-1.2 Cr; 1.2-2.5 Ni, in which the ratio of the content of Cr and Ni is 1: (1.7-2.8). 2. The roll according to claim 1, characterized in that the depth of the outer working layer is 40-55 mm with a maximum caliber radius of not more than 35 mm.