GB2262745A

GB2262745A - Use of a steel for cold-rollers.

Info

Publication number: GB2262745A
Application number: GB9226777A
Authority: GB
Inventors: Karl Steinhoff; Edmund Haberling; Wilfried Hueckelhoven
Original assignee: Steinhoff & Co oHG GmbH; Thyssen Edelstahlwerke AG
Current assignee: Steinhoff & Co oHG GmbH; Thyssen Stahl AG
Priority date: 1991-12-24
Filing date: 1992-12-23
Publication date: 1993-06-30
Anticipated expiration: 2012-12-23
Also published as: FR2685348A1; FR2685348B1; DE4143012A1; BE1006545A3; GB9226777D0; ES2054582B1; ES2054582A1; GB2262745B; DE4143012C2

Description

1 2262745 Use of a steel for cold-rollers The present invention relates to

the use of a steel for coldrollers.

Steels used for cold-rollers which are usual in the trade, have the composition shown in Table 1.

Table 1

Short name Material Chemical Composition in No. c S Mn Cr Mo v W 86 CrMoV7 1.2327 0.85 0.3 0.3 1.8 0.3 0.1 X210Cr12 1.2080 2.00 - - 12.0 - X155CrWo12 1 1.2379 1.55 - - 12.0 0.7 1.0 X63CrMoV5 1 1.2362 0.63 1.1 0.4 5.2 1.5 0.5 S6-5-2 1.3343 0.90 4.0 5.0 1 1.9 6.4 1 From DE-Patent No 30 06 512 wear-resistant cold-rollers are known, which are hardened in depth and made of a steel containing 0.7 to 0.9 % C, 0.2 to 2.0 % Si, 0.2 to 1.0 % Mn, 2. 5 to 3. 5 % Cr, 0. 5 to 2. 0 % -Mo, 0. 7 to 1. 5 % Ni and 0. 1 to 0.8 % V. Safety against fracture of the rollers is ensured by a mild cooling agent, such as oil, after the austenitising. This has a result that the steels have to be alloyed with up to 1.5% Ni in order to reach a sufficient hardening depth. The wear resistance is achieved by the addition of up to 0.8 % V. Vanadium in alloy steel does not form a pure Vanadium carbide of the VC-type, but mixed (MC-) carbides, in which also other alloy elements, such as chromium and molybdenum are dissolved. MC-carbides, however, are not very stable. During the hardening of the rollers they are partially dissolved thereby releasing in their environment a high content of carbon into the matrix. This results in an undesired localised stabilisation of residual austenite. On one hand the danger of breaks and tension cracks is higher, whilst on the other hand, the wear resistance is lower.

1 1 It is the aim of the invention to provide a steel for coldrollers which has an increased wear resistance.

Thus, according to the invention there is provided a steel having (in weight %) more than 0.7 to 1.0 % C 0.1 to 1.5 % Si 0.1 to 1.5 % Mn 1.8 to 3.5 % Cr 0.1 to 1.0 % Mo 0.1 to 1.0 % Ni 0.05 to 1.0 % Nb as well as optionally up to 0.8 % V, up to 2.0 % W, up to 0.05 % B, rest iron and impurities from smelting. Preferably, for the named use there is provided a steel having (in weight more than 0.70 0.30 0.10 2.0 0.10 0.10 to 0. 95 % C to 1. 5 % Si to 1. 0 Mn to 3.0 Cr to 0.7 Mo to 0.7 Ni 0. 10 to 0.5 V 0. 10 to 0.5 Nb rest iron and impurities from smelting.

Furthermore, for the proposed use there is suggested a steel having on average the following composition (in weight 0.85 c 1.0 si 0.3 Mn 2.5 Cr 0.5 Mo 0.3 Ni 0.2 V 0.1 Nb rest iron and impurities from smelting.

2 1 Particularly by using cold-rollers of diameter of up to goo mm and a width of up to 3000 mm, after solution treatment (austenitising at 800 to 1000 'C) followed by abrupt chilling, a hardening depth of up to 30 mm, relative to 60 HRC (700 HV30) with a roller diameter of 600 mm is achieved.

The steel according to the present invention has a matrix which can be hardened and in which are embedded nearly insoluble, stable niobiumcarbides (NbC). Cold rollers made from this steel, preferably of a diameter of up to 900 mm and a width of up to 3000 mm, are subjected to solution treatment at 800 to 1000C and chilled abruptly. Thereby greater hardening depth can be achieved. The niobiumcarbides embedded into the matrix are not influenced during austenitising and thereby neither change the hardening of the rollers nor the portion of residual austenite through emission of carbon. Thereby, the danger of tension cracks and sheeting which could result in bad accidents and damage is reduced. In contrast, the wear resistance, which results from the niobium carbides which are embedded in the matrix and which have a hardness of approximately 3000HV, is fully maintained.

An addition of up to 2 % tungsten can even increase the hardness and the resistance to wear. An addition of up to 0.050 % B increases the hardness, the depth of the hardness and the fine grain composition of the steel.

Figure 1 illustrates the surface hardness and the depth of the hardness of cold rollers made either of a steel according to the present invention or of a known steel. The analysis therefrom is shown in Table 2.

Table 2

Steel c si Mn Cr Mo Ni v Nb 1. 2327 0.85 0.3 0.3 1.8 0.3 0.1 Invention 0.8 1.0 0.3 2.5 0.55 0.2_, 0.2 3 At the same surface hardness of 800 HV30, the hardness of a cold roller made from steel B according to the present invention only drops at a depth of 30 mm compared to 20 mm in the known comparable steel 1.2327 on 700 HV30.

The average increase in performance achieved by the rollers made of the steel according to the present invention, owing to the reduced wear during the rolling of bands of steel, is approximately 20 %. Additional advantages result from longer standing times of the rollers and their increased sheetingand crack-security which reduces the stand still times of rolling mill trains caused by a change of rollers.

4

Claims

1. A steel having the following composition (weight -.) more than 0.7 to 1.0 % C 0.1 to 1.5 Si 0.1 to 1.5 Mn 1.8 to 3.5 Cr 0.1 to 1.0 Mo 0.1 to 1.0 Ni 0.05 to 1.0 Nb as well as up to 0. 8 up to 2. 0 up to 0.05 rest iron optionally % v, % W, % B, and impurities from smelting.

2. A steel according to claim 1 having the following composition:

more than 0.70 to 0.95 C 0.30 to 1.5 % Si 0.10 to 1.0 % Mn 2.0 to

3.0 Cr 0.10 to 0.7 mo 0.10 to 0.7 Ni 0.10 to 0.5 V 0.10 to 0.5 % Nb rest iron and impurities from smelting.

6 3. A steel according to claim 1 having substantially the following components on average 0.85 1.0 0.3 2.5 0.5 0.3 0.2 0.1 0-0 c si Mn Cr MO Ni v 0-0 Nb rest iron and impurities from smelting.

4. A niobium-containing steel substantially as described and exemplified herein.

5. Use of a steel according to any preceding claim for the production of cdld rollers.

6. A process for the production of a cold roller of a diameter of up to 90Omm and a width of up to 3000 mm from steel according to any of claims 1-4, the process comprising solution treatment (austenitising at 8000 to 1000 "C) followed by abrupt chilling, whereby the resulting roller has a hardening depth of up to 30mm, relative to 60 HRC (700 HV30) at roller diameters of

7 60Omm.

1 7. A cold roller made from a steel according to any of claims 1-4.

8. A cold roller according to claim 7 substantially as described and exemplified herein.