DD244569A1 - ROLLER BODY OR BANDAGE FOR HOT ROLLING MILLS MANUFACTURED IN THE SLOTTED CASTING METHOD - Google Patents

Abstract

The invention relates to rollers produced by centrifugal casting and bandages for hot rolling mills of wire and fine steel. These have a shell-hard casting structure and contain the following alloying elements: 2.4-4.0% C; 0.3-3.6% Ni; 0.4-2.0% Cr; 0.8-1.2% Mn; 0.3-2.4% Si as well as the usual accompanying and residual elements. It is intended to minimize the use of the centrifugal casting process, the alloying elements to save the heat treatment and to achieve long service life. In this case, a Gefuegestruktur is set, which gives the roller body with high Oberflaechenhaerte sufficient machinability. According to the invention, the cast iron additionally contains carbide-stabilizing fine grain formers, such as up to 1% V, up to 0.5% Ti and up to 1% Nb (V / Ti 2: 1). This results in a ledeburitic cementite matrix (at least ZEG4) with embedded, fine-grained carbide with a low Graphiteinschlessen. It reaches a hardness of about 80 HShD.

Description

Field of application of the invention

The invention relates to roll bodies or drums produced by the centrifugal casting process for hot rolling mills, in particular wire and fine steel mills, having shell casting structures containing the following conventional alloying elements,

2.4-4.0% C 0.3-3.6% Ni 0.4-2.0% Cr 0.8-1.2% Mn 0.3-2.4% Si

with the usual accompanying and residual elements in the working shift.

Characteristic of the known technical solutions

The materials used for roll bodies in hot rolling mills can be divided essentially into the following groups:

- High alloyed cast iron with high contents of chromium or nickel, as well as tungsten, vanadium and molybdenum, which increase the heat resistance and make the machinability difficult. Due to these high alloy contents, these rolls are relatively expensive also in view of the ever increasing world market prices;

White or gray solidified cast iron rolls called "indefinite" rolls These rolls may optionally be subjected to a heat treatment to obtain required hardness at the surface and toughness in the core;

- Rollers of nodular cast iron (GGG). For this purpose, an alloying of the melt with magnesium or other master alloys is required so that they form the responsible for the good material properties spherical graphite precipitates;

- There are also known rolling elements of hard metals, with priority carbide carbides are processed in the sintering to roll bodies. These materials are very expensive only at very high rolling speeds with good cooling on wire lines in use and in production based on Co;

- Furthermore, centrifugal casting and composite casting rolls are also known which have different material properties and microstructures in the shell and in the core.

In DE-OS 32 36 268 a wear-resistant cast iron alloy with relatively low alloy contents anSi, Mn, Ni and increased levels of Cr, Mo, W, V and Co is disclosed. From this it is preferable to make roll rings, which are then subjected to a heat treatment by hardening and tempering.

The disadvantages of the known roller bodies are that they either require relatively high contents of Cr, Ni, W, V, Mo or Co and / or are associated with a subsequent heat treatment.

Object of the invention

The invention aims to avoid the disadvantages of the known roller bodies and to find a roller material with minimized alloy contents, which, adapted to the centrifugal casting process, subsequently requires no heat treatment and guarantees a long service life.

-2- 244 569 Explanation of the nature of the invention

The invention has for its object to develop a material for roll body or bandages, which forms a microstructure when using the centrifugal casting, which still gives the roller body with high wear resistance sufficient machinability.

According to the invention, this object is achieved in that the cast iron additionally contains carbide-stabilizing fine grain formers in the following proportions

to 1% V to 0.5% Ti to 1% Ni

with a maximum ratio V / Ti = 2: 1 and a ledeburitic, basic cementite matrix of at least ZEG4 with embedded, fine-grained carbide fractions with low graphite inclusions having a hardness of up to 80HShD. Advantageously, this material for roll body or bandages can still contain up to 0.2% Nb.

embodiment

The invention will be explained in more detail below with reference to two material compositions according to the invention.

1. It was made a working layer of less than 50 mm thickness for a finish roller with 0320 mm. The melt contained 3.6% C; 0.5% Ni; 0.5% Cr; 1.1% Mn and with the following additives in the pan alloyed 0.3% V and 0.15% Ti.

The centrifugal casting was carried out at a Kokillenneigung of 20 ° at a speed of 690 U / min. The structure was ledeburitic, cementitic with insignificant graphite precipitates. The hardness of the working layer was determined by a specially calibrated test method = 600 Hv or ^ 80HSh-D. When rolling smooth and flat dimensions for a fine steel rolling mill in the end stands caliber increases in performance of 01.3fach compared to hard shell casting rollers of the known type GHKNiCr530 were achieved.

2. There was a base alloy cast iron with 2.7% C; 0.5% Si; 0.6% Mn; 0.5% Cr for the working layer of a rebar roll 0320mm melted.

In the pan, the following additives were added

0.4% V; 0.1% Ti and 0.2% Nb.

The centrifugal casting was carried out at a Kokillenneigung of 20 ° at a speed of 500 rev / min. The structure consists of a ledeburitic matrix with insignificant graphite precipitates. The hardness of the working layer was determined by a specially calibrated test method to be 500 HV or 67HShD. These rolls were used in a fine steel mill and achieved a caliber increase performance of 01.2 times over a roll of the known type GHG400. Ribbed profiles were incorporated with conventional impaction cutters.

Claims (2)

Claim: 1. Rolled bodies or drums produced by centrifugal casting for hot rolling mills, in particular wire and fine steel mills, having shell casting structures containing the following conventional alloying elements 2.4-4.0% C
, 0.3-3.6% Ni 0.4-2.0% Cr 0.8-1.2% Mn 0.3-2.4% Si with the usual accompanying and residual elements, characterized in that the cast iron additionally contain carbide-stabilizing fine grain formers in the following proportions * up to 1% V to 0.5% Ti to 1% Ni with a maximum ratio V / Ti = 2: 1 and a ledeburitic, cementitic matrix of at least ZEG4 with embedded fine-grained carbide with low Graphiteinschlüssen having a hardness up to 80HShD. 2. Roller bodies or bandages produced by centrifugal casting for hot rolling mills according to claim 1, characterized in that the cast iron additionally contains up to 0.2% Nb.