EP1769098A1

EP1769098A1 - Steel strip for spreading knives, doctor blades and crepe scrapers and powder metallurgical method for producing the same

Info

Publication number: EP1769098A1
Application number: EP05772787A
Authority: EP
Inventors: Manfred DAXELMÜLLER; Helmut Ponemayr
Original assignee: Voestalpine Precision Strip GmbH
Current assignee: Voestalpine Precision Strip GmbH
Priority date: 2004-07-19
Filing date: 2005-07-07
Publication date: 2007-04-04
Also published as: WO2006007984A1; CN101128613A; KR20070048197A; BRPI0513482A; US7722697B2; TW200611984A; CA2573630A1; DE102004034905A1; CN100540710C; US20080096037A1; JP2008506844A

Abstract

The invention relates to a steel strip (1) for producing spreading knives, doctor blades or crepe scrapers. Said steel strip has a steel composition which is constituted, in weight percent, by 1 - 3 % C, 4 - 10 % Cr, 1 - 8 % Mo, 2.5 - 10 % V and the remainder iron and impurities in normal proportions, whereby the steel strip (1) is produced using a powder metallurgical method. The invention also relates to spreading knives, doctor blades and crepe scrapers produced from said steel strip and to a method for producing the same.

Description

Steel strip for doctor blades, applicator knives and creping scrapers and pul¬ metallurgical process for their preparation

Technical area

The invention relates to a cold-rolled steel strip having a thickness of 0.05 to 1.2 mm, which is used as a material for the production of doctor blades, applicator blades and creping doctor.

State of the art

In the paper industry, doctor blades or doctor blades are used in the form of thin, long knives to coat the paper web with a coating slip. These knives are pressed against the moving paper web, whereby a counterpressure is usually provided by a counter roll or a knife on the opposite side of the paper web if a double-sided coating is to be carried out. The application knife must be straight if a uniform coating of the best quality is to be achieved. The usual specification states that the machined edge of the applicator may not deviate more than 0.3 mm per 3000 mm applicator length from the complete straightness.

In order to meet these requirements, a steel alloy must be selected which prevents the bands from forming during hardening and tempering when the steel strips are subjected to these processes. It is known that in this respect alloy steels pose more problems than unalloyed steels, and this is especially true for steel alloys containing several different interacting alloying elements. Consequently, the most common material for order knives is still lenstoffstahl. A typical composition of such a steel is, for example, (in% by weight) 1.00% C, 0.30% Si, 0.40% Mn, 0.15% Cr and the remainder iron and impurities in normal proportions. Martensitic stainless steel is also used for the production of commissioned knives, eg the steel with the composition (in% by weight) 0.38% C, 0.5% Si, 0.55% Mn, 13.5% Cr, 1 , 0 Mo and the rest iron and impurities in normal proportions.

In the paper industry, creping scrapers are used under the same conditions as described above in order to obtain a specific creping of the paper. High demands are also placed on the straightness of the working edge.

Also in the printing industry band-shaped coating tools are used, which are known as putties. They are similar to those used in the paper industry. These spatula must also meet high requirements regarding their straightness. The same material is used for both spatulas and applicators.

Application knives are highly stressed when using abrasive pigments in the material applied to the paper surface, as well as by the base paper, and worn at the edge. Spreading knives are also heavily stressed by the color pigments in the order ink which are applied by the doctor blades. Accordingly, it is desirable that both applicator blade and doctor blade have a high abrasion resistance and consequently a long service life.

However, neither carbon steel blade nor martensitic stainless steel blade meets this requirement. Consequently, it is common practice to replace the blades in the paper machine after just a few hours of operation. Of course, this is particularly detrimental due to the production losses during the replacement of the knife. EP 0 672 761 B1 describes a steel which has the following composition (in% by weight) 0.46% -0.70% C, 0.2% -0.5% Si, 0.1 % - 2.0% Mn, 1.0% - 6.0% Cr, 0.5% - 5% Mo, 0.5% - 1.5% V, max. 0.01% B, max. 1.0% Ni, max. 0.2% Nb and the balance iron and impurities in the normal proportions. The steel is suitable for the production of thin cold-rolled strips and, in its hardened and tempered state, can be used for the production of applicator and / or doctor blades. The cold rolling process comprises a hardening step with an austenitization at 1000 ° C., followed by an annealing step in a lead bath at a temperature between 240 ° C. and 270 ° C. Application and / or doctor blades made from this material have good abrasion resistance and straightness and their lifespan is 12 - 16 hours.

It is also known that the abrasion resistance of alloyed steel can be higher than that of non-alloyed steel. This is advantageous for certain tool and construction steels. Some examples of these are the alloy steels described in JP-A-61/41749 and in US 4,743,426 and US 2,565,264 which are used for guide pins in plastic molds or hot-forming steels, e.g. are designed for high temperature aluminum extrusion dies as well as turbine blades, forging tools, cutting tools and similar products, and are made from billet or bar stock. However, steel alloys of this type have not been used for the production of thin, cold-rolled, hardened and tempered belts for applicators and doctor blades and for creping shears, presumably because during cold rolling and heat treatment of the belt, major problems may arise Cracking, deviation from the straightness and similar defects can lead, making the material for applicators and / or doctor or creping doctor is unsuitable.

An already known method for increasing the lifetime of the doctor blades is to coat the edges with a ceramic layer. This significantly increases the effective life of the doctor blades. The ceramic coating However, thesinks are very expensive and are therefore not used so often.

In a further different approach, which is described in WO 02/35002, a bimetal coating blade is proposed. In this case, the carrier band of the coating blade consists of a tough elastic steel on which an abrasion-resistant strip of HSS is applied in order to increase the stability of the coating blade. These bimetal coating blades have disadvantages in terms of strength in the transition carrier tape - edge due to the material differences. Furthermore, such a bimetal coating blade is very expensive to manufacture and therefore expensive.

In order to increase the service life of such applicator blades and doctor blades, it is conceivable to increase the content of the carbide-forming components, for example molybdenum (Mo), vanadium (Va), chromium (Cr) or tungsten (W) and carbon in the corresponding ratio. However, during the conventional manufacturing process, during solidification of the melt, these components tend to form large carbide crystals in the steel.

However, such large carbide crystals are undesirable in applicators and doctor blades, since the material around the hard carbide crystals wears out more heavily than the carbide crystals themselves during use of the knives. Therefore, after a certain period of use at the working edge of the knives, the carbide crystals come out of the mold surrounding steel. This can lead to undesirable grooves in the paper surface or streaks in the coating of the paper. Furthermore, by means of said carbide crystals, the counter-roll, which is usually coated with plastic, can be damaged.

The applicator blade and doctor blade are first hot rolled from a block into a hot strip, which is then cold rolled to a steel strip having a thickness of 0.05 mm - 1.2 mm and a width of 10 mm - 250 mm. conventional However, traditionally produced steel strips with a high carbide content have a limited cold workability. They tend to embrittle, so that Stahlbän¬ often show cracks after forming when cold-formed to the dimensions mentioned above.

Therefore, it is the problem of the present invention to provide a steel strip for the production of applicator knives, doctor blades and creping blades, which have an improved life and yet can be produced inexpensively.

Summary of the invention

The above-mentioned problem is solved by a steel strip according to patent claim 1, applicator knife, doctor blade or creping doctor according to one of claims 25 - 26 or by a method for producing the same according to patent claim 28.

In particular, the problem is solved by a steel strip for the production of doctor blades, applicators or creping doctor having a Stahlzu¬ composition comprising in percent by weight

1 - 3% C

4 - 10% Cr

1 - 8% mo

2.5-10% V

and the rest essentially iron and impurities in normal

Ratios, where

the steel strip is produced using a powder metallurgy process. The powder metallurgy manufacturing process can produce a steel of the above composition which has a high carbide content yet can be formed into a steel strip for doctor, applicator or creping doctor without embrittlement or cracking. In the following, doctor blades, doctor blades and creping doctor are summarized under the term "knife". Furthermore, a steel strip according to the invention has a large number of small carbide crystals, so that the knives produced therefrom wear uniformly at their edge and no scoring occurs in the paper or streaking in the paper coating. In addition, knives of the steel strip according to the invention have a high wear resistance, without a complex and expensive manufacturing process was used. The strength disadvantages that occur with a Bimetallsteichklinge can not occur in the uniform material of the steel strip according to the invention.

Preferably, the steel strip according to a thickness of 0.05 - 1.2 mm, and / or a width of 10 - 250 mm.

In a preferred embodiment, the steel strip is produced using a cold rolling process. Due to the fine grain of the structure, the cold rolling on the above. Dimensions only possible.

Further constituents of the steel composition result from the subclaims. In preferred embodiments, the steel composition cumulatively or alternatively comprises the following components in the following parts by weight:

1.5-3% C;

Traces up to a maximum of 1.1% Si, preferably 0.8-1.1% Si, and more preferably 1.0% Si;

Traces up to a maximum of 1% Mn, preferably 0.4-0.5% Mn; Nothing more than impurities of W;

Instead of Mo 2 - 16% W;

Nothing more than impurities of Co;

Traces up to a maximum of 12% Co;

6-10% Cr, preferably 6.5-8.5% Cr;

1 - 2% Mo, preferably 1.5% Mo;

4 - 10% V;

1.0-2.5% C, preferably 1.2-2.3% C;

1% Si, preferably 0.5% Si;

Traces up to a maximum of 1% Mn, preferably 0.3% Mn;

4-5% Cr, preferably 4.2% Cr;

4 - 8% Mo, preferably 6 - 7% Mo;

6-7% W, preferably 6.4-6.5% W;

2 - 7% V, preferably 3.0 - 6.5% V; and or

7-12% Co, preferably 8-11% Co. The steel strip preferably has a working edge which has a hardness of 500-600 HV, preferably 575-585 HV and / or a straightness of 0.3 mm / 3000 mm strip length.

In a further embodiment, the working edge is hardened, preferably laser beam-hardened. This has the advantage that a very targeted introduction of heat energy into the material is possible without the use of a vacuum environment.

An applicator blade made of a steel strip according to the invention preferably has a thickness of 0.25-0.64 mm. A doctor blade made of a steel strip according to the invention preferably has a thickness of 0.15-1.0 mm. A creping doctor made from a steel strip according to the invention preferably has a thickness of 0.25-1.2 mm.

The above-mentioned problem is further solved by a method for the production of applicator knives, doctor knives or creping scrapers, wherein the method comprises the following steps in this order:

a) powder metallurgical production of a steel block with a steel composition according to the invention;

b) hot rolling the steel block into a steel strip; and

c) cold rolling the steel strip into a strip having a maximum thickness

1.2 mm.

The step of cold rolling is preferably carried out by means of edge supports. In a further preferred embodiment, after the step of cold rolling, a hardening step is carried out at a temperature of 950-1050 ° C., followed by an annealing step at a temperature of 550-650 ° C.

Cold rolling, curing and tempering preferably take place in a continuous process.

Further preferably, the hardening step comprises a cooling step, wherein the strip is cooled between cooling plates to a temperature of 150-25O ⁰ C.

Preferably, the working edge of the belt is hardened, preferably by means of a load beam.

Brief Description of the Drawings Preferred embodiments will now be described with reference to the drawings. It shows:

1 is a three-dimensional view of a Stahlban¬ invention in the rolled up state;

FIG. 2 shows a three-dimensional view of a partial section of a steel strip according to the invention for illustrating a first edge shape; FIG.

3 shows a three-dimensional view of a partial section of a steel strip according to the invention for clarifying the dimensions and a second one

Edge shape;

4 shows two schematic three-dimensional microscopically enlarged partial sections of the edge material of a steel strip, wherein on the left a steel strip ^{* of} the prior art and on the right a steel strip according to the invention is shown; and Fig. 5 shows two microscopically enlarged grinding Bildaurhahmen of Kantenmateri¬ than a steel strip, on the left a steel strip of the prior art and on the right an erfϊndungsgemäßes steel strip is shown.

Description of the preferred embodiments

In the following, preferred embodiments of the present invention will be explained.

As mentioned above, the invention relates to the use of a special Stahl¬ alloy with a special composition for the production of knives (applicator and doctor blade, scraper, creping doctor, blades, doctor blade, scraper) in the form of cold-rolled, hardened and annealed tapes.

Fig. 1 shows a three-dimensional view of a erfmdungs contemporary steel strip 1 in the rolled up state, as provided for shipping. FIG. 3 shows the dimensions. Typically, the width B is between 10 and 250 mm, while the thickness of the applicator blades is between 0.05 and 1.2 mm and, in a typical case, between 0.25 and 0.64 mm. For doctor blades, the thickness in a typical case is between 0.15 and 1.0 mm. Creping scrapers have a typical thickness of 0.25 - 1.2 mm.

As shown in FIG. 3, the machined edge 20 of a blade can either be straight, ie have a 90 ° angle. However, the edge 10 can also be bevelled, as shown in FIG. This is an edge shape that is also used for applicator and doctor blades.

The content of the various alloying elements and their significance for the steel for this particular field of application will be explained in detail below. 1st embodiment

According to a first embodiment of the present invention, carbon should be present in the steel in sufficient quantities to give it a basic hardness sufficient to withstand the pressure against the paper web or inking roll without being subjected to permanent deformation, and also during annealing to form MC carbides. MC carbides cause precipitation hardening and thus improved abrasion resistance of the edge. The carbon content should therefore be at least 1% C and preferably 1.50%. The maximum carbon content is 3% C.

Vanadium should be present in the steel in order to form very small MC carbides during the tempering or annealing by precipitation. It is believed that these MC carbides are the main reason for the surprisingly good abrasion resistance of the doctor blades of the present invention. The carbides have a submicroscopic size, which means a maximum size of the order of magnitude of between 1 and 3 μm. In order to provide a sufficiently high volume fraction of MC carbides, the vanadium content should be at least 4% V. The vanadium content should not exceed 10% V.

The chromium content should whom ^'gstens 6% Cr, preferably at least 6.5% Cr betra¬ gene to impart sufficient hardenability to the steel, ie it quenching in air or after austenitization in martensite wah¬ rend umzu¬ form. However, chromium is also carbide-forming, which is why it competes with vanadium for the carbon in the steel matrix. The higher the chromium content, the less stable are the vanadium carbides. However, chromium carbides do not form the precipitation hardening, which is desirable and can be formed by the vanadium in the above-mentioned amounts. Chromium in larger amounts also creates a higher risk of retained austenite. Therefore, the chromium content in the steel is limited to 10%, preferably to at most 8.5%. The molybdenum content should be at least 1%, so that it can form MC carbides together with vanadium and can positively contribute to the formation of these carbides. Since molybdenum is present in the MC carbides, they dissolve more easily during austenitization when curing takes place and then form part of the MC carbides formed during annealing. However, the molybdenum content must not be so high that disadvantageous amounts of molybdenum carbides are formed which, like chromium carbides, are unstable and grow at high temperatures. The molybdenum content should therefore be limited to 2%, preferably to 1.5%.

Molybdenum can be replaced in the usual way completely or partially by twice the amount of tungsten. Therefore, in a preferred embodiment, the alloy composition should not have tungsten exceeding an impurity level.

The manganese content in the steel is limited to 1% and, like chromium, contributes to giving the steel the desired hardenability. The manganese content is preferably 0.4- 0.5% Mn.

The silicon content should be at least 0.8% in order to increase the carbon activity in the steel and to accelerate the precipitation of the small vanadium carbides during annealing. The increased carbon activity, however, can also lead to a faster coarsening of the carbides, resulting in a faster softening of the steel. In other words, the tempering curve is shifted to the left, and the hardness maximum is shifted upward when the silicon content is high. However, the steel should not contain more than at most 1.1% silicon and preferably not more than 1.0% silicon.

Nickel does not provide any positive contribution to the steel in the desired application. Nickel may affect the heat treatment of the product Steel. Therefore, the steel is best not more nickel than at Verunreini¬ supply level.

Otherwise, the steel contains essentially nothing but iron. Other elements, including, for example, aluminum, nitrogen, copper, cobalt, titanium, niobium, sulfur and phosphorus are present in the steel only as impurities or as unavoidable minor elements.

In this first embodiment, three different steel alloys were powder metallurgically produced, cold rolled and tested with good results. The three alloys were cold rolled into thin strips of 0.05-1.2 mm thickness and 10-250 mm width and can be used for the production of doctor blades, calipers and creping doctor blades. The nominal compositions of these steel alloys were as follows:

1.5% C, 1% Si, 0.4% Mn ₅ 8% Cr ₅ 1.5% Mo ₅ 4% V and the remainder iron and un¬ avoidable impurities.

2.1% C, 1% Si, 0.4% Mn, 6.8% Cr ₅ 1.5% Mo, 5.4% V and the remainder iron and unavoidable impurities.

2.9% C, 1% Si, 0.5% Mn, 8% Cr, 1.5% Mo, 9.8% V and the balance iron and unavoidable impurities.

2nd embodiment

According to a second embodiment of the present invention Koh¬ should lenstoff present in sufficient amounts to give it a basic hardness, sufficient to endure being ^'pressed against the paper web or ink application roll, respectively, without suffering permanent deformations in the steel, as well as to form MC carbides during annealing. MC carbides cause a precipitation hardening and thus an improved Abrasion resistance of the edge. The carbon content should therefore be at least 1.0% C and preferably 1.2%. The maximum carbon content is 2.5% C, preferably 2.3% C.

Vanadium should be present in the steel in order to form very small MC carbides during the tempering or annealing by precipitation. It is believed that these MC carbides are the main reason for the surprisingly good abrasion resistance of the doctor blades of the present invention. The carbides have a submicroscopic size, which is a maximum size of the order of 1 .mu.m-3 .mu.m. means. In order to provide a sufficiently high volume fraction of MC carbides, the vanadium content should be at least 2.5% V, preferably at least 3.0% V. The vanadium content should not exceed 7% V and preferably the steel contains at most 6.5% vanadium.

In this embodiment, the chromium content is lower. The chromium content should be at least 4% Cr in order to lend sufficient hardenability to the steel, i. to transform it into martensite during quenching in air or after austenitisation. However, chromium is also carbide-forming, which is why it competes with vanadium for the carbon in the steel matrix. The higher the chromium content, the less stable the vanadium carbides are. The chromium content in the steel can be 5%. The nominal proportion is approximately 4.2% Cr.

The molybdenum content should be at least 4%, so that it can form MC carbides together with vanadium and can positively contribute to the formation of these carbides. Since molybdenum is present in the MC carbides, they dissolve more easily during austenitization when curing takes place and then form part of the MC carbides formed during annealing. However, the molybdenum content must not be so high that disadvantageous amounts of molybdenum carbides are formed which, like chromium carbides, are unstable and at high temperatures Temperatures are growing. The molybdenum content should therefore be limited to 8% Mo, preferably between 5-7% Mo, in this second embodiment.

Molybdenum can be replaced in the usual way completely or partially by twice the amount of tungsten. Tungsten improves the abrasion resistance, increases the hardening temperature and improves the heat resistance. According to this second embodiment, the steel contains 6-7% W, preferably about 6.4-6.5% tungsten.

The manganese content in the steel is limited to 1% and, like chromium, contributes to giving the steel the desired hardenability. The manganese content is preferably 0.3% Mn.

The silicon content should be at least 0.8% in order to increase the carbon activity in the steel and to accelerate the precipitation of the small vanadium carbides during annealing. The increased carbon activity, however, can also lead to a faster coarsening of the carbides, resulting in a faster softening of the steel. In other words, the tempering curve is shifted to the left, and the hardness maximum is shifted upward when the silicon content is high. However, the steel should not contain more than 0.8% silicon at most and preferably not more than 0.5% silicon.

Nickel does not provide any positive contribution to the steel in the desired application field. Nickel may affect the heat treatment of the steel. Therefore, in this second embodiment, the steel is best not containing more nickel than at the impurity level.

According to this second embodiment of the present invention, the steel contains cobalt in an amount of at least 8%. Cobalt improves the hot workability of the steel. However, cobalt makes the steel more brittle and increases the formation hardening in the cold forming operations. Therefore, the steel should not more than 12% cobalt, preferably not more than 11%. Improved hot workability is not a critical property for the steel, and therefore this second embodiment of the invention essentially does not contain cobalt.

In this second embodiment, three different steel alloys were powder metallurgically produced, cold rolled and tested with good results. The three alloys were cold-rolled into thin strips having a thickness of 0.05-1.2 mm and a width of 10-250 mm and can be used for the manufacture of knives. The nominal compositions of these steel alloys were as follows:

1.28% C, 0.5% Si, 0.3% Mn, 4.2% Cr, 5% Mo, 6.4% W, 3.1% V and the balance iron and unavoidable impurities.

1.28% C, 0.5% Si, 0.3% Mn, 4.2% Cr, 5% Mo, 6.4% W, 5.4% V, 8.5% Co and the balance iron and unavoidable impurities.

2.3% C, 0.5% Si, 0.3% Mn, 4.2% Cr, 7% Mo, 6.5% W, 6.5% V, 10.5% Co and the balance iron and unavoidable impurities.

The applicator or doctor blade and the creping doctor are produced according to the vor¬ underlying invention as follows. An alloy having the desired composition described above and in the claims is prepared using a powder metallurgy process. The powder is mixed in the desired composition and compacted into compact blocks by hot isostatic pressing. The blocks then become Hot rolled strips of thickness of about 3 - 3.5 mm. Then the strips are cold rolled to a desired thickness of less than 1.2 mm. Alter¬ nierend intermediate heating steps can be performed. In order to avoid edge cracks on the tapes 1, when the thickness is reduced from about 3.5 mm to 1 mm, cold rolling is performed by means of edge supports. When the strip 1 has reached its final thickness T during the cold rolling, it is subsequently hardened and tempered in a continuous process.

The cold-rolled strips 1 of the first embodiment are cured using Austenitisierung at a temperature of 950 ° C - 1050 ° C, followed by quenching between cooling plates to a temperature of 15O ⁰ C - 25O ⁰ C and a tempering or Annealing at 550 ^° C.-650 ^° C.

The cold-rolled strips 1 of the second embodiment are Verwen¬ dung austenitization at a temperature of 1000 ⁰ C - hardened 1050 ⁰ C, followed by quenching between cooling plates to a temperature of 150 ⁰ C - 25O ⁰ C and tempering or annealing at 550 ⁰ C - 65O ⁰ C.

This is followed by brushing the surfaces of the bands 1. If desired, the bands 1 can be dyed by annealing in an oxidizing atmosphere. The bands 1 are cut to the correct length and width B, and the edge 10, 20 is processed by sizing and / or grinding to obtain the desired edge profile.

By means of the method according to the invention, cold-rolled strips with a width of up to 250 mm could be produced, without having to forego a sufficient straightness of the working edge. But also the flatness of the band is of crucial importance. The working edge should have a straightness of 0.3 mm / 3000 mm strip length. The flatness should be at least 0.3% of the nominal bandwidth according to the Pilhöjld standard. In addition, the bands are characterized by working edges 10, 20, which have improved properties. In particular, they have an increased abrasion resistance in comparison to other tapes available today.

According to an alternative embodiment, the working edge 10, 20 can be hardened by means of local heating of the edge region, for example by means of induction hardening. Preferably, curing by means of a high energy jet may also be used, for example laser, plasma or electron beam curing, which gives the working edge 10, 20 a certain hardened area which does not affect the straightness of the belt. Preferably, a laser beam is used for this purpose. The working edge 10, 20 hardened in this way achieves an improved hardness of up to 630 HV, preferably 620 HV.

Furthermore, the working edge 10, 20 of a steel strip according to the invention by the powder metallurgical production process on a particularly fine microstructure ge. FIGS. 4 and 5 show microscopic enlargements of the microstructure of the working edge 10, 20. The left-hand illustration in FIGS. 4 and 5 shows a structure 30 according to the prior art, which was produced by means of a conventional melting process. There are shown schematically large hard cards 34, 36 which are embedded in a surrounding alloy 32. After a certain period of use, the working edge 10, 20 wears, whereby the carbides 34, 36 wear less strongly than the surrounding material 32. As a result, the carbides on the surface protrude from the rest of the structure, as in the case of the carbide with the reference numeral 36 is shown. Such hervor¬ standing carbides produce on the paper surface or the backing roll grooves or stripes in the coating of the paper, so that the blades must be replaced.

On the right side of Fig. 4 and 5, a structure 40 of a working edge 10, 20 according to the invention is shown. The structure 40 has the same steel composition. However, it was produced by means of a powder metallurgical process. This results in fine, well distributed carbides 44 which are embedded in the surrounding structure 42. A working edge 10, 20 with such a structure 40 wears off evenly and without protruding carbides 36 and therefore does not lead to a scoring or banding.

The method according to the invention, which makes it possible to successfully produce cold-rolled strips with widths of up to 250 mm, makes it possible for a plurality of narrow strips to be produced simultaneously. In this case, a wide strip 1 is cut into several narrow strips before the edges 10, 20 are machined. In this way, for example, by means of a single cold rolling operation of a wide band two narrow bands can be obtained.

Claims

claims

1. Steel strip (1) for the production of doctor blades, applicators or creping scrapers comprising:

a) a steel composition comprising by weight

1 - 3% C 4 - 10% Cr 1 - 8% Mo

2.5-10% V

and the remainder essentially iron and impurities in normal proportions, wherein

b) the steel strip is produced using a powder metallurgical process.

2. Steel strip according to claim 1, comprising

a) a thickness of 0.05 - 1.2 mm, and / or

b) a width of 10 - 250 mm.

3. Steel strip according to one of claims 1 or 2, wherein it is further prepared using a cold rolling process.

4. Steel strip according to any one of claims 1-3, wherein the Stahlzusammenset¬ tion 1.5-3% C has.

5. Steel strip according to any one of claims 1-4, wherein the steel composition further comprises traces of up to a maximum of 1.1% Si, preferably 0.8-1.1% Si, and more preferably 1.0% Si.

6. Steel strip according to one of claims 1-5, wherein the steel composition further comprises traces of up to a maximum of 1% Mn, preferably 0.4-0.5% Mn.

7. A steel strip according to any one of claims 1-6, wherein no more than impurities of W are contained in the steel composition.

8. Steel strip according to any one of claims 1-6, wherein the Stahlzusammenset¬ tion instead of Mo 2% - 16% W contains.

9. Steel strip according to one of claims 1-8, wherein no more than impurities of Co are contained in the Stahlzusammenset¬ tion.

10. Steel strip according to one of claims 1-8, wherein the steel composition further comprises traces of up to a maximum of 12% Co.

11. Steel strip according to one of claims 1-10, wherein the steel composition comprises 6 - 10% Cr, preferably 6.5 - 8.5% Cr.

12. Steel strip according to one of claims 1-11, wherein the steel composition has 1 - 2% Mo, preferably 1.5% Mo.

13. Steel strip according to one of claims 1-12, wherein the steel composition has 4 - 10% V.

The steel strip according to claim 1, wherein the steel composition has 1.0 - 2.5% C, preferably 1.2 - 2.3% C.

The steel strip according to claim 14, wherein the steel composition further comprises traces to a maximum of 1% Si, preferably 0.5% Si.

16. steel strip according to any one of claims 14 or 15, wherein the Stahlzusam¬ composition further comprises traces to a maximum of 1% Mn, preferably 0.3% Mn.

17. Steel strip according to any one of claims 14-16, wherein the Stahlzusammenset¬ tion has 4 - 5% Cr, preferably 4.2% Cr.

18. Steel strip according to one of claims 14-17, wherein the steel composition has 4 - 8% Mo, preferably 6 - 7% Mo.

19. Steel strip according to one of claims 14 - 18, wherein the steel composition has 6 - 7% W, preferably 6.4 - 6, 5% W.

20. Steel strip according to any one of claims 14 - 19, wherein the Stahlzusammenset¬ tion has 2 - 7% V, preferably 3.0 - 6.5% V.

21. Steel strip according to any one of claims 14-20, wherein no more than impurities of Co are contained in the Stahlzusammen¬.

22. Steel strip according to one of claims 14-20, wherein the steel composition further comprises 7-12% Co, preferably 8-11% Co.

23. StahlBaπd according to one of claims 1 - 22, comprising a working edge (10, 20) which has a hardness of 500-600 HV, preferably 575 - 585 HV and / or a straightness of 0.3 mm / 3000 mm strip length.

24. Steel strip according to one of claims 1 - 23, wherein the working edge (10, 20) hardened, preferably laser beam-cured.

25. An applicator made of a steel strip (1) according to any one of claims An¬ 1-24, having a thickness of 0.25 - 0.64 mm.

26. doctor blade, made of a steel strip (1), according to one of Ansprü¬ che 1 - 24, having a thickness of 0.15 - 1.0 mm.

27. Creping doctor, made of a steel strip (1), according to one of Ansprü¬ che 1 - 24, having a thickness of 0.25 - 1.2 mm.

28. A method of making calipers, doctor blades or creping doctor blades, the method comprising the following steps in this order:

d) powder metallurgical production of a steel block with a Stahlzusam¬ composition according to one of claims 1 - 22;

e) hot rolling the steel block into a steel strip; and

f) cold rolling of the steel strip into a strip (1) with a thickness of max. 1.2 mm.

29. The method according to claim 28, wherein the step of cold rolling is performed by means of edge supports.

30. The method according to any one of claims 28 or 29, wherein after the step of cold rolling, a curing step at a temperature of 950 - 1050 ⁰ C. followed by an annealing step at a temperature of 550 - 65O ⁰ C.

31. The method of claim 30, wherein the cold rolling, the curing and the tempering proceeds in a continuous process.

32. The method according to any one of claims 30 or 31, wherein the hardening step ei¬ nen cooling step, wherein the strip (1) between cooling plates to a temperature of 150 - 25O ⁰ C is cooled.

33. The method according to any one of claims 28 - 32, wherein the working edge (10, 20) of the strip (1) cured, preferably laser beam-cured.