U.S. patent application number 10/583207 was filed with the patent office on 2007-07-12 for edge-provided tool and method for the manufacture thereof.
Invention is credited to Maria Sundqvist, Bertil Walden.
Application Number | 20070158045 10/583207 |
Document ID | / |
Family ID | 30768834 |
Filed Date | 2007-07-12 |
United States Patent
Application |
20070158045 |
Kind Code |
A1 |
Sundqvist; Maria ; et
al. |
July 12, 2007 |
Edge-provided tool and method for the manufacture thereof
Abstract
The invention relates to an edge-provided tool, such as a doctor
blade, for use as wiping tool in the production of pulp and/or
paper in different stages of the production process. It consists of
an edge-provided strip of steel, the edge portion of which has been
provided with a wear-resistant coating applied by means of laser
technique, so that metallurgical binding is present between said
coating and the steel strip, whereby a level of surface hardness of
more than 850 UV being attained. Thereby, wear-resistant doctor
blades having a long service life have been obtained.
Inventors: |
Sundqvist; Maria;
(Sandviken, SE) ; Walden; Bertil; (Sandviken,
SE) |
Correspondence
Address: |
DILWORTH & BARRESE, LLP
333 EARLE OVINGTON BLVD.
SUITE 702
UNIONDALE
NY
11553
US
|
Family ID: |
30768834 |
Appl. No.: |
10/583207 |
Filed: |
December 10, 2004 |
PCT Filed: |
December 10, 2004 |
PCT NO: |
PCT/SE04/01839 |
371 Date: |
June 16, 2006 |
Current U.S.
Class: |
162/281 ;
118/414; 15/256.51; 250/492.1; 427/508 |
Current CPC
Class: |
D21G 3/005 20130101;
C23C 30/005 20130101; C23C 24/10 20130101; C23C 26/02 20130101 |
Class at
Publication: |
162/281 ;
015/256.51; 118/414; 250/492.1; 427/508 |
International
Class: |
C23C 24/00 20060101
C23C024/00; D21G 3/00 20060101 D21G003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 19, 2003 |
SE |
0303516-9 |
Claims
1. Doctor or coater blade, in particular for use as wiping, scraper
and/or cleaning tool in production of paper pulp and/or paper in
different stages of the production process, comprising an
edge-provided strip of steel, the edge portion of which has been
provided with a wear-resistant coating, wherein the edge portion of
the blade is coated with surface-reinforcing coating applied by
laser technique, so that the metallurgical binding is present
between said wear-resistant coating and the steel strip, and the
edge portion has a hardness of more than 1000 HV.
2. Doctor or coater blade according to claim 1, wherein the
wear-resistant coating has a level of surface hardness of at least
850 HV.
3. Doctor or coater blade according to claim 1, wherein the edge
portion of the blade has a surface layer applied by laser coating,
the thickness of which layer constitutes 5-15% of the thickness of
the blade.
4. Doctor or coater blade according to claim 1, wherein the edge
portion of the blade has a surface-reinforcing portion applied by
laser coating or laser impregnation, the thickness of which portion
constitutes 5-15% of the thickness of the blade.
5. Doctor or coater blade according to claim 1 wherein the steel is
a carbon steel with a chemical composition in % by weight being
0.8-1.2% of C, preferably about 1% of C, 0.20-0.35% of Si,
0.35-0.50% of Mn, maximum 0.02% of P, maximum 0.01% of S, with Fe
as balance and the content of some additional element in the
periodic system in contents below 0.5%.
6. Method for the manufacture of a doctor or coater blade according
to claim 1 wherein a material manufactured from steel is first
rolled out and edge-treated to have an edge portion formed along
one of the edges, said edge portion then is provided with a
surface-reinforcing layer applied by laser technique, in such a way
that a metallugical binding arises between said layer and the
subjacent steel substrate, and the edge treatment is provided in
the way that the steel substrate is subjected to a laser treatment
during supply of powder at such a supply of heat that the powder is
fused with the steel substrate while forming an
atomic/metallurgical binding.
7. Method for the manufacture of a doctor or coater blade according
to claim 1 wherein a material manufactured from steel is first
rolled out and edge-treated to have an edge portion formed along
one of the edges, said edge portion then is provided with a
surface-reinforcing layer applied by laser technique, in such a way
that a metallugical binding arises between said layer and the
subjacent steel substrate, and the edge treatment is provided in
the way that the steel substrate is subjected to a laser
impreganation and recovery, material particles of a ceramic
material penetrating into the surface melt by laser, so that an
atomic/metallurgical binding arises.
8. Method according to claim 6, wherein the supplied powder
essentially contains aluminum oxide.
9. Method according to claim 6, wherein the supplied material
essentially contains stellite.
10. Method according to claim 7, wherein the impregnation is
carried out in the way that carbides and nitrides, such as TiC, NbC
and/or TiN, are supplied to the steel substrate.
11. Method according to claim 6, wherein the chemical composition
of the steel in % by weight is 0.8-1.2% of C, preferably about 1%
of C, 0.20-0.35% of Si, 0.35-0.50% of Mn, maximum 0.02% of P,
maximum 0.01% of S, with Fe as balance and the content of some
additional element in the periodic system in contents below
0.5%.
12. Method according to claim 6, wherein the wear-resistant coating
has a level of surface hardness of more than 850 HV.
13. Doctor or coater blade according to claim 2, wherein the steel
is a carbon steel with a chemical composition in % by weight being
0.8-1.2% of C, preferably about 1% of C, 0.20-0.35% of Si,
0.35-0.50% of Mn, maximum 0.02% of P, maximum 0.01% of S, with Fe
as balance and the content of some additional element in the
periodic system in contents below 0.5%.
14. Doctor or coater blade according to claim 3, wherein the steel
is a carbon steel with a chemical composition in % by weight being
0.8-1.2% of C, preferably about 1% of C, 0.20-0.35% of Si,
0.35-0.50% of Mn, maximum 0.02% of P, maximum 0.01% of S, with Fe
as balance and the content of some additional element in the
periodic system in contents below 0.5%.
15. Doctor or coater blade according to claim 4, wherein the steel
is a carbon steel with a chemical composition in % by weight being
0.8-1.2% of C, preferably about 1% of C, 0.20-0.35% of Si,
0.35-0.50% of Mn, maximum 0.02% of P, maximum 0.01% of S, with Fe
as balance and the content of some additional element in the
periodic system in contents below 0.5%.
16. Method according to claim 7, wherein the supplied powder
essentially contains aluminum oxide.
17. Method according to claim 7, wherein the supplied material
essentially contains stellite.
18. Method according to claim 7, wherein the chemical composition
of the steel in % by weight is 0.8-1.2% of C, preferably about 1%
of C, 0.20-0.35% of Si, 0.35-0.50% of Mn, maximum 0.02% of P,
maximum 0.01% of S, with Fe as balance and the content of some
additional element in the periodic system in contents below
0.5%.
19. Method according to claim 7, wherein the wear-resistant coating
has a level of surface hardness of more than 850 HV.
20. Method according to claim 16, wherein the impregnation is
carried out in the way that carbides and nitrides, such as TiC, NbC
and/or TiN, are supplied to the steel substrate.
Description
[0001] Scraper or cleaning blades denominated "doctor blades" are
widely used in the paper and pulp industry for different purposes,
but in most cases they have the function of cleaning or scraping
off material or left-overs from the surface of a rotary roller.
Such doctor blades have, for instance, the purpose of detaching a
paper web from a stiff drying cylinder by scraping the surface of
the cylinder.
[0002] The paper pulp contains filler such as silicon dioxide,
great particles and paper fibers that wear out the doctor blade,
the wear being substantially evenly distributed along the edge, and
wherein it holds that the rate of wear is greater than the rate of
corrosion. Furthermore, the doctor blade is seen as an article of
consumption having very short service life, usually considerably
smaller than one day. In many cases, it is exchanged already after
approximately 5 hours. Usually no regrinding of the doctor blade is
carried out but it is discarded when consumed.
[0003] There are different principles in the paper mills for the
use of doctor blades, with the same in general being worn-in
initially for the formation of an edge. When the same has been
formed, the wear is relatively even. The proper
"in-situ"-grinding-in is assumed to have a quality-influencing
effect on the manufactured paper. If the doctor blade is used in a
later stage of the production process of paper, it influences the
paper quality and the surface structure of the paper, and therefore
it is seen as a very critical parameter. The doctor blades may be
of different length and vary between about 1 and 10 m.
[0004] Thus, since a doctor blade is subjected to extensive wear,
different techniques are used in order to extend the service life
thereof, such as addition of wear-resistant material on the part of
the blade that meets the cylinder. As an example of such a
reinforcement of the top or edge surface of the blade, ceramic hard
coatings are presently used as a practical solution to bring down
the blade wear. Such ceramic coatings are usually applied to a
doctor blade made by hardened and annealed carbon steel and may be
applied by thermal spraying, such as plasma spraying or plasma
depositing.
[0005] Examples of techniques to provide such wear-resistant
coatings on cleaning or scraper blades of the type doctor blades
(in English "doctor blade") are found in GB-A-978 988, GB-A-1 289
609 and GB-A-2 130 924. The entire known technique is aimed at the
provision of a wear-resistant coating on the part of the blade that
comes into contact with the surface of a rotary cylinder.
[0006] According to prior art, with the purpose of improving the
properties of the edge-provided tool, service life and thereby
influence the paper quality, thermal (warm) spraying with HVOF
("High Velocity Oxygen Fuel") is, among other things, used. The
method gives sintering of the additive material and so-called
diffusion binding at about 1000.degree. C. Problems with this
coating method are cracks, pores, poor binding strength, adhesion
problems, etc. Materials sprayed today are ceramics, such as
Al.sub.2O.sub.3.
[0007] Against this background, it is an object of the present
invention to be able to provide an edge-provided tool, such as a
doctor blade, which tool has been provided with a coating having
better adhesion than that of hitherto known tools. Simultaneously,
deformations of the tool arising otherwise should be tried to be
minimized, at the same time as desired fineness requirements and
absence of scratches on the completed paper product should be
possible to meet. Furthermore, the supply of energy or influence of
heat on the base material made by the surface treatment should as
far as possible be minimized.
[0008] An additional object of the present invention is to produce
a scraper and/or cleaning blade of primarily doctor blade type,
which possesses long service life and which in the paper
manufacture imparts the paper a smooth and fine surface, free from
scratches and other defects.
[0009] These and additional objects have in a surprising way
succeeded to be attained by providing the tool with the features
defined in the independent claims. Preferred embodiments of the
present invention are defined in the dependent claims.
[0010] The invention will be closer described below in connection
with the drawing figures, where
[0011] FIG. 1 shows a perspective view of a doctor blade applied in
direct connection to a roller so as to wiping off the paper pulp in
the production of paper;
[0012] FIG. 2 shows an explanatory sketch of an edge-treated doctor
blade according to the present invention;
[0013] FIG. 3 shows an explanatory sketch of a coated doctor blade
edge according to the invention, seen from the side;
[0014] FIG. 4 shows an explanatory sketch of a laser-impregnated
doctor blade edge according to the invention, seen from the side;
and
[0015] FIG. 5 shows an explanatory sketch showing laser coating of
a doctor blade according to the invention.
[0016] Thus, the present invention relates to an edge-provided tool
as well as a method for the manufacture thereof. More closely
defined, the invention relates to a type of tool that is called
"doctor blade" and that is a wiping, scraper and/or cleaning tool
used in, for instance, the manufacture of paper, in order to get a
smooth and fine paper product free from scratches and other
defects. Also tools that usually are called coater blades, and also
general knives, are comprised in the present invention. However,
with the purpose of facilitating the description of the invention,
the subject of the invention will below be designated "doctor
blade", in which concept also other denominations are intended to
be comprised.
[0017] Thus, FIG. 1 shows a doctor blade 1, which abuts against a
roller 2 and, for instance, scrapes away pulp from the same. As a
preferred example of materials that have turned out to work well in
order to coat the edge portion of the material by means of laser
technique according to the invention, steel grades having a
hardness of at least 450 HV have been selected. An example of such
a steel is a carbon steel having a composition comprising (in % by
weight) 0.8-1.2% of C, preferably about 1% of C, 0.20-0.35% of Si,
0.35-0.50% of Mn, maximum 0.02% of P, maximum 0.01% of S, with Fe
as balance and the content of some additional element in the
periodic system in contents below 0.5%.
[0018] FIGS. 2 and 3 show a steel strip 3, which on the edge
thereof has been coated with a coating 4 by laser technique in
accordance with the invention. Thereby, the resistance to wear is
increased considerably. The coating is composed of, for instance,
aluminum oxide or stellite (for instance stellite 12). The laser
technique is, per se, well known to a person skilled in the art and
is visualized in FIG. 5. In the laser coating, the atomic (also
called "metallurgical") binding to the steel substrate
characteristic of the invention is attained, which is visualized in
FIG. 3.
[0019] FIG. 4 shows a doctor blade in cross-section, which has been
coated with, for instance, TiC in accordance with the present
invention. The laser impregnation technique is described in the
patent WO 99/56906. The steel strip is designated 5 and the
impregnation applied by means of laser technique is designated 6.
Also in this figure it is visualized that the particles/the
carbides have penetrated into the steel substrate, whereby the
limit between the two to a significant extent having been erased.
The coating has been effected with, for instance, aluminum oxide or
stellite, such as in the FIGS. 2 and 3, while the impregnation is
carried out with suitable carbides and/or nitrides.
[0020] According to FIG. 5, the surface-reinforcing portion in the
formed edge portion of a strip-shaped doctor blade is provided in
the way that, by means of laser technique, a coating, supplied by
means of powder material 7, is applied to the edge under such
supply of heat that the powder is fused with the basic material in
the doctor blade, so that atomic and metallurgical binding arise.
The supply of heat takes place by means of a laser gun 8, a coating
9 being provided on the substrate. The supplied material in the
flow of powder 7 suitably consists of a refractory material, such
as aluminum oxide. Alternatively, a material such as stellite may
be used. In connection with the coating 9 having been applied to
the doctor blade, it is important that the material can undergo a
quick cooling, so that a desired fine structure is obtained, which
is characterized by both toughness and hardness, more closely
defined to a level of hardness corresponding to 850-1300 HV. In
this way, simultaneously high bearing strength in the surface layer
is attained at the same time as requirements of low friction and
desired corrosion resistance can be fulfilled.
[0021] As has been mentioned above, the coating may essentially be
composed of aluminum oxide or stellite. However, the coating may
also contain or be composed of other refractory materials, such as
metallic oxides, metallic silicates, metallic carbides, metallic
borides, metallic nitrides and mixtures thereof. Especially
preferred ceramic materials are selected among aluminum oxide,
chromic oxide, zirconium oxide, wolfram carbide, chromium carbide,
zirconium carbide, tantalum carbide, titanium carbide, titanium
nitride, niobium carbide and borides.
[0022] As has been mentioned above, a laser impregnation may also
be carried out by, for instance, carbides and nitrides such as TiC,
NbC and TiN being added to the surface of the base material during
the laser treatment. The particles are added by spraying under high
gas pressure at the same time as the laser beam locally melts the
surface layer on the material so that the wear-resistant particles
can penetrate into the substrate. Furthermore, the laser coating
may be effected in a plurality of rounds, so that multiple layers
are obtained. The steel strip then receives a very wear-resistant
surface.
[0023] The thickness of the steel strip is the normal one for
doctor blades in the paper industry and may vary between 0.2 and 3
mm, suitably between 0.305 and 1.27 mm. The thickness of the
coating or the impregnation may suitably be between 5 and 15% of
the thickness of the steel strip.
* * * * *