U.S. patent application number 10/560935 was filed with the patent office on 2007-04-12 for double walled metal tube, metal band and strip, and method of coating a metal strip.
This patent application is currently assigned to Hille & Muller GMBH. Invention is credited to Peter Arthur Boehmer, Dieter Otto Paul Junkers.
Application Number | 20070082215 10/560935 |
Document ID | / |
Family ID | 33395917 |
Filed Date | 2007-04-12 |
United States Patent
Application |
20070082215 |
Kind Code |
A1 |
Junkers; Dieter Otto Paul ;
et al. |
April 12, 2007 |
Double walled metal tube, metal band and strip, and method of
coating a metal strip
Abstract
The invention relates to a double walled metal tube comprising a
tubular roll formed metal band having a brazing layer between the
metal layers of the tubular roll formed metal band, wherein the
brazing layer consists of a copper alloy. According to the
invention, the copper alloy is a copper-tin alloy, wherein the
copper-tin alloy contains 3-12 wt % tin. The invention also relates
to a metal band for forming such a double walled metal tube and to
a metal strip for producing such metal bands, and to a method of
coating a metal band and strip.
Inventors: |
Junkers; Dieter Otto Paul;
(Aach, DE) ; Boehmer; Peter Arthur; (Zemmer/Rodt,
DE) |
Correspondence
Address: |
STEVENS DAVIS MILLER & MOSHER, LLP
1615 L STREET, NW
SUITE 850
WASHINGTON
DC
20036
US
|
Assignee: |
Hille & Muller GMBH
Am Trippelsberg 48
Dusseldorf
DE
40589
|
Family ID: |
33395917 |
Appl. No.: |
10/560935 |
Filed: |
June 16, 2004 |
PCT Filed: |
June 16, 2004 |
PCT NO: |
PCT/EP04/06537 |
371 Date: |
October 10, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60482028 |
Jun 25, 2003 |
|
|
|
Current U.S.
Class: |
428/548 ;
428/586 |
Current CPC
Class: |
Y10T 428/12028 20150115;
B21C 37/09 20130101; B60T 17/04 20130101; F16L 9/18 20130101; Y10T
428/12292 20150115; B21C 37/154 20130101; F16L 9/165 20130101; B23K
35/302 20130101 |
Class at
Publication: |
428/548 ;
428/586 |
International
Class: |
B22F 7/02 20060101
B22F007/02; F01D 5/18 20060101 F01D005/18 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 18, 2003 |
EP |
03076903.8 |
Claims
1. Double walled metal tube comprising a tubular roll formed metal
band having a brazing layer between the metal layers of the tubular
roll formed metal band, wherein the brazing layer consists of a
copper alloy, the copper alloy being a copper-tin alloy, wherein
the copper-tin alloy comprises 3-12 wt % tin.
2. Double walled metal tube according to claim 1, wherein the
copper-tin alloy comprises 6-8 wt % tin.
3. Double walled metal tube according to claim 1, wherein the
copper-tin alloy comprises about 7 wt % tin.
4. Double walled metal tube according to claim 1, wherein the metal
band is made of steel.
5. Double walled metal tube according to claim 1, wherein the steel
band is made of mild steel.
6. Double walled metal tube according to claim 1, wherein the metal
band from which the tube has been roll formed has a coating of a
nickel layer on one side.
7. Metal band for producing double walled metal tubes according
claim 1, the metal band having a width of essentially 20-80 mm,
wherein a coating layer is present on at least one side of the
metal band for brazing the metal band, the coating layer being a
copper-tin alloy, wherein the copper-tin alloy comprises 3-12 wt %
tin.
8. Metal band according to claim 7, wherein the copper-tin alloy
comprises 6-8 wt % tin.
9. Metal band according to claim 7, wherein the copper-tin alloy
layer is present on both sides of the metal band.
10. Metal band according to claim 7, wherein the metal band has a
coating of a nickel layer on one side of the metal band.
11. Metal band according to claim 7, wherein the metal band
consists of steel.
12. Metal strip for making metal bands for producing double walled
metal tubes according to claim 1, wherein a coating layer for
brazing purposes is present on at-least one side of the metal
strip, the coating layer being a copper-tin alloy, wherein the
copper-tin alloy comprises 3-12 wt % tin.
13. Metal strip according to claim 12, wherein the copper-tin alloy
comprises 6-8 wt % tin.
14. Metal strip according to claim 12, wherein the copper-tin alloy
layer is present on both sides of the metal strip.
15. Metal strip according to claim 12, wherein the metal strip has
a coating of a nickel layer on one side of the metal strip.
16. Metal strip according to claim 12, wherein the metal strip
consists of steel.
17. Method of coating a metal strip with a coating layer consisting
of a copper-tin alloy comprising the following steps: cleaning the
metal strip; activating the surface of the metal strip;
continuously coating at least one side of the metal strip with a
copper-tin alloy layer comprising 3-12 wt % tin; posttreating the
metal strip.
18. Method according to claim 17, wherein the metal strip is coated
with a copper-tin alloy layer comprising 6-8 wt % tin.
19. Method according to claim 17, wherein the metal strip is
continuously coated with a layer of nickel on one side of the metal
strip.
20. Method according to claim 17, wherein the metal band is coated
using Physical Vapour Deposition (PVD), comprising the following
steps: cleaning the metal strip; drying the metal strip; activating
the metal strip; continuously coating at least one side of the
metal strip with a copper-tin alloy layer comprising 3-12 wt % tin;
cooling of the coated strip; applying an anti-oxidising agent.
21. Method according to claim 17, wherein the metal band is coated
using electroplating.
22. Method according to claim 17, wherein the metal band is coated
with a copper-tin alloy layer in a tin ion and copper ion
containing cyanide bath.
23. Double walled metal tube according to claim 1, wherein the
steel band is made of mild steel having a composition of 0.03-0.07%
C, .ltoreq.0.02% P, .ltoreq.0.015% S, .ltoreq.0.06% Si, 0.05-0.4%
Mn, 0.02-0.07% Al (all percentage in weight), the remainder Fe and
unavoidable impurities.
24. Metal band according to claim 7, wherein the copper-tin alloy
comprises about 7 wt % tin.
25. Metal band according to claim 7, wherein the copper-tin alloy
layer is present on both sides of the metal band, the copper-tin
alloy layer having a thickness of 0.5-5 .mu.m on each side
26. Metal band according to claim 7, wherein the copper-tin alloy
layer is present on both sides of the metal band, the copper-tin
alloy layer having a thickness of 3-5 .mu.m on one side and 0.5-1.5
.mu.m on the other side
27. Metal band according to claim 7, wherein the copper-tin alloy
layer is present on both sides of the metal band, the copper-tin
alloy layer having a thickness of about 4 .mu.m on one side and
about 1 .mu.m on the other side.
28. Metal band according to claim 7, wherein the metal band has a
coating of a nickel layer on one side of the metal band having a
thickness of 0.5-2 .mu.m on one side of the metal band and a
copper-tin alloy layer having a thickness of 3-5 .mu.m on the other
side of the metal band.
29. Metal band according to claim 7, wherein the metal band
consists of mild steel.
30. Metal band according to claim 7, wherein the metal band
consists of mild steel having a composition of 0.03-0.07% C,
.ltoreq.0.02% P, .ltoreq.0.015% S, .ltoreq.0.06% Si, 0.05-0.4% Mn,
0.02-0.07% Al (all percentage in weight), the remainder Fe and
unavoidable impurities.
31. Metal strip according to claim 12, wherein the copper-tin alloy
comprises about 7wt % tin.
32. Metal strip according to claim 12, wherein the copper-tin alloy
layer is present on both sides of the metal strip, the copper-tin
alloy layer having a thickness of 0.5-5 .mu.m on each side.
33. Metal strip according to claim 12, wherein the copper-tin alloy
layer is present on both sides of the metal strip, the copper-tin
alloy layer having a thickness of on one side and 0.5-1.5 .mu.m on
the other side
34. Metal strip according to claim 12, wherein the copper-tin alloy
layer is present on both sides of the metal strip, the copper-tin
alloy layer having a thickness of about 4 .mu.m on one side and
about 1 .mu.m on the other side.
35. Metal strip according to claim 12, wherein the metal strip has
a coating of a nickel layer on one side of the metal strip, the
nickel layer having a thickness of 0.5-2 .mu.m on one side of the
metal strip and a copper-tin alloy layer having a thickness of 3-5
.mu.m on the other side of the metal strip.
36. Metal strip according to claim 12, wherein the metal strip
consists of mild steel.
37. Metal strip according to claim 12, wherein the metal strip
consists of mild steel having a composition of 0.03-0.07% C,
.ltoreq.0.02% P, .ltoreq.0.015% S, .ltoreq.0.06% Si, 0.05-0.4% Mn,
0.02-0.07% Al (all percentage in weight), the remainder Fe and
unavoidable impurities.
38. Method of coating a metal strip with a coating layer consisting
of a copper-tin alloy comprising the following steps: cleaning the
metal strip; activating the surface of the metal strip;
continuously coating at least one side of the metal strip with a
copper-tin alloy layer comprising 3-12 wt % tin; posttreating the
metal strip comprising applying an anti-oxidising agent.
39. Method according to claim 17, wherein the metal strip is coated
with a copper-tin alloy layer comprising about 7 wt % tin.
40. Method according to claim 17, wherein the metal strip is
continuously coated with a layer of nickel on one side of the metal
strip before the coating of the copper-tin alloy layer.
41. Method according to claim 17, wherein the metal band is coated
using electroplating, using a copper plated layer and a tin plated
layer, the coated metal being subsequently annealed to produce a
copper-tin alloy.
Description
[0001] This application claims priority from European patent
application 03076903.8 filed on 18 Jun. 2003 and U.S. Provisional
patent application 60/482,028 filed on 25 Jun. 2003 both of which
are incorporated herein by reference.
[0002] The present invention relates to a double walled metal tube
comprising a tubular roll formed metal band having a brazing layer
between the metal layers of the tubular roll formed metal band. The
invention also relates to a metal band wherein a coating layer is
present on at least one side of the metal band for brazing the
metal band and to a metal strip wherein a coating layer is present
on at least one side of the metal strip, and to a method of coating
the metal strip. The term metal band is used here to indicate a
narrow strip, cut from a normal (wide) strip usually having a width
of 500 mm or more.
[0003] Double walled metal tubes that are made of a tubular roll
formed metal band having a brazing layer between the metal layers
of the tubular roll formed metal band are well known and are mainly
used for brake lines of motor vehicles; other applications are for
example hydraulic tubes or refrigerator tubes. Such double walled
metal tubes possess two layers of metal and are manufactured from a
flat metal band that is provided on at least one side with a
brazing layer. The metal band is roll formed and subsequently
brazed. As brazing material in the automotive industry copper is
used, because copper has a melting point of 1081.degree. C., so the
brazing temperature in the brazing apparatus and the brazing time
can be controlled well. The metal of the tube usually is mild
steel, having a composition of 0.03-0.07% C, .ltoreq.0.02% P,
.ltoreq.0.015% S, .ltoreq.0.06% Si, 0.05-0.4% Mn, 0.02-0.07% Al
(all percentage in weight), the remainder Fe and unavoidable
impurities. An additional corrosion-preventing coating is often
applied over the brazed double walled tube.
[0004] In U.S. Pat. No. 5,553,640, which is focused on double
walled tubes of stainless steel, it is proposed to use a brazing
layer having a lower melting point to reduce the risk of grain
boundary diffusion and to increase the corrosion resistance of the
material. The brazing layer according to this patent is a copper
alloy comprising 13 to 15% tin or 32.5 to 37% zinc or 15 to 18%
silver. These amounts of tin, zinc and silver have been chosen to
get a brazing temperature in the vicinity of the eutectic point so
as to achieve the greatest possible reliability for producing the
brazing connection.
[0005] These copper alloys however each have their disadvantages.
The copper-tin alloy has a brazing temperature of 800-820.degree.
C. The copper-zinc alloy has a brazing temperature just above
900.degree. C. The copper-silver alloy has a brazing temperature
below 1000.degree. C. Due to the used alloys and the brazing
temperatures, the strength of these alloys is lower than the
strength of pure copper as brazing layer. The automotive industry
has not used these alloys for lo producing double walled metal
tubes for brake lines in view of the lower strength, the cost for
implementing these alloys and the potential risk associated with
changing a long established, proven process.
[0006] It is an object of the present invention to provide a double
walled metal tube for brake lines of motor vehicles and the like,
that is easier and more economical to manufacture than the
presently produced double walled tubes. It is also an object of the
invention to provide such a tube that is acceptable for the
automotive industry. Moreover, a metal band and strip and a
manufacturing method for such a strip are provided.
[0007] According to a first aspect of the invention there is
provided a double walled metal tube comprising a tubular roll
formed metal band having a brazing layer between the metal layers
of the tubular roll formed metal band, wherein the brazing layer
consists of a copper alloy, the copper alloy being a copper-tin
alloy, wherein the copper-tin alloy comprises 3-12wt % tin.
[0008] A double walled metal tube with a brazing layer of a
copper-tin alloy comprising 3-12wt % tin has a lower melting point
than the brazing layer of pure copper, which means that the brazing
temperature in the apparatus for producing the tubes can be lower
and the length of tube produced per minute can be higher. This is
an economical advantage for the automotive industry.
[0009] On the other hand, the percentage tin in the brazing alloy
is rather low. With this percentage tin, the brazing seam strength
requirements posed by the automotive industry are met. Moreover,
because the percentage tin is low, the modification of the brazing
process for the double walled tubes will allow the use of the
existing brazing devices. It will be understood that tin is the
main alloying element in the copper-tin alloy, but that small
amounts of other elements could be present.
[0010] Preferably, in the double walled tube the copper-tin alloy
comprises 6-8 wt % tin. A tin percentage between 6 and 8 provides a
considerable reduction of the brazing temperature, whereas at the
same time the strength of the brazed tube is well above the minimum
required strength.
[0011] According to a most preferred embodiment the double walled
metal tube has a brazing layer of copper-tin alloy comprising
essentially 7 wt % tin. This percentage tin is deemed to give an
optimum for the requirements of both low brazing temperature and
high strength of the brazing layer. The brazing temperature is
below 1000.degree. C.
[0012] Preferably, the metal band of the double walled metal tube
is made of steel. The preferred steel for brake lines for motor
vehicles is mild steel, for instance a mild steel having a
composition of 0.03-0.07% C, .ltoreq.0.02% P, .ltoreq.0.015% S,
.ltoreq.0.06% Si, 0.05-0.4% Mn, 0.02-0.07% Al (all percentage in
weight), the remainder Fe and unavoidable impurities. However,
stainless steel is also possible in view of the lower brazing
temperature, which reduces the risk of grain boundary
diffusion.
[0013] According to a preferred embodiment of the double walled
metal tube the metal band from which the tube has been roll formed
has a coating of a nickel layer on one side. This has the advantage
that a corrosion resistant layer is present on the tube, either on
the inside or on the outside of the tube, depending on the way the
metal band has been roll formed. For double walled metal tubes to
be used in brake lines for automotive purposes, the nickel layer is
preferably present on the outside of the tube. For double walled
metal tubes to be used in fuel lines for automotive purposes the
nickel layer is preferably present on the inside of the tube.
[0014] According to a second aspect of the invention there is
provided a metal band, the metal band having a width of essentially
20-80 mm, wherein a coating layer is present on at least one side
of the metal band for brazing the metal band, the coating layer
being a copper-tin alloy, wherein the copper-tin alloy comprises
3-12 wt % tin. This metal band can be used for producing the double
walled tube according to the first aspect of the invention.
[0015] Preferably, the copper-tin alloy layer on the metal band
comprises 6-8 wt % tin, preferably essentially 7 wt % tin. This
percentage tin in the alloy is optimal for producing a double
walled tube.
[0016] According to a preferred embodiment of the metal band, the
copper-tin alloy layer is present on both sides of the metal band,
the copper-tin alloy layer preferably having a thickness of 0.5-5
.mu.m on each side, more preferably 3-5 .mu.m on one side and
0.5-1.5 .mu.m on the other side, and still more preferably about 4
.mu.m on one side and about 1 .mu.m on the other side. The metal
strip with these copper-tin alloy layers can easily be brazed when
roll formed into a double walled metal tube.
[0017] According to another preferred embodiment, the metal band
has a coating of a nickel layer on one side of the metal band,
preferably a nickel layer having a thickness of 0.5-2 .mu.m on one
side of the metal band and a copper-tin alloy layer having a
thickness of 3-5 .mu.m on the other side of the metal band. This
metal band provides a band that can easily be brazed when roll
formed into a double walled metal tube using the copper-tin alloy
layer, and at the same time provides a corrosion resistant layer on
the outside or the inside of the formed tube using the nickel
layer.
[0018] Preferably the metal band consists of steel, preferably mild
steel, the mild steel preferably having a composition of 0.03-0.07%
C, .ltoreq.0.02% P, .ltoreq.0.015% S, .ltoreq.0.06% Si, 0.05-0.4%
Mn, 0.02-0.07% Al (all percentage in weight), the remainder Fe and
unavoidable impurities. Mild steel is usually preferred for double
walled tubes for brake lines, but stainless steel could also be
used.
[0019] According to a third aspect of the invention there is
provided a metal strip, wherein a coating layer for brazing
purposes is present on at least one side of the metal strip, the
coating layer being a copper-tin alloy, wherein the copper-tin
alloy comprises 3-12 wt % tin. This strip can be used for making
metal bands for producing double walled metal tubes according to
the first aspect of the invention.
[0020] Preferably, the copper-tin alloy of the coating on the metal
strip comprises 6-8 wt % tin, preferably essentially 7 wt % tin.
This percentage is optimal for the production of double walled
metal tubes for brake lines for automotive applications.
[0021] According to a preferred embodiment, the copper-tin alloy
layer is present on both sides of the metal strip, the copper-tin
alloy layer preferably having a thickness of 0.5-5 .mu.m on each
side, more preferably 3-5 .mu.m on one side and 0.5-1.5 .mu.m on
the other side, and still more preferably about 4 .mu.m on one side
and about 1 .mu.m on the other side. The bands cut from this strip
can easily be brazed when roll formed into a double walled metal
tube.
[0022] According to another preferred embodiment, the metal strip
has a coating of a nickel layer on one side of the metal strip,
preferably a nickel layer having a thickness of 0.5-2 .mu.m on one
side of the metal strip and a copper-tin alloy layer having a
thickness of 3-5 .mu.m on the other side of the metal strip. This
metal strip can be cut into bands that are easily brazeable when
roll formed into a double walled metal tube using the copper-tin
alloy layer, and at the same time provide a corrosion resistant
layer on the outside or the inside of the formed tube using the
nickel layer.
[0023] According to a fourth aspect of the invention, there is
provided a method of coating a metal strip with a coating layer
consisting of a copper-tin alloy comprising the following steps:
[0024] cleaning the metal strip; [0025] activating the surface of
the metal strip; [0026] continuously coating at least one side of
the metal strip with a copper-tin alloy layer comprising 3-12 wt %
tin; [0027] posttreating the metal strip (e.g. applying an
anti-oxidising agent). The continuous coating of the metal strip
with a coating layer of a copper-tin alloy comprising 3-12 wt % tin
provides metal bands, cut from this metal strip, that can be used
for making double walled tubes for brake lines for motor vehicles
according to the first aspect of the invention.
[0028] Preferably, the metal strip is coated with a copper-tin
alloy layer comprising 6-8 wt % tin, preferably essentially 7 wt %
tin. This tin percentage is optimal for such double walled tubes.
The metal of the strip does not influence the coating, but is
preferably mild steel for double walled tubes for automotive
purposes or for other purposes. However, the metal could also be
stainless steel.
[0029] According to a preferred embodiment of the method, the metal
strip is continuously coated with a layer of nickel on one side of
the metal strip, preferably before the coating of the copper-tin
alloy layer. The coating with a nickel layer provides a metal strip
with both a nickel layer and at least one copper-tin alloy layer,
which is advantageous for producing double walled metal tubes from
bands cut from this strip, because in this way the tubes are
provided with a corrosion preventive nickel layer.
[0030] According to a preferred method the metal band is coated
using Physical Vapour Deposition (PVD). This coating method is
known as such, and suitable for coating a metal strip. The coating
layers can be applied as two sided coating for the copper-tin alloy
layer, or as one-sided coating for the nickel coating and/or the
copper-tin alloy coating. PVD is known for its environmental
friendly processes and flexibility, and the cost is comparable to
electroplating. The PVD coating of copper-tin alloy can be applied
as one layer of copper-tin alloy, or as a separate copper and a
separate tin layer that are subsequently diffusion annealed.
[0031] According to another preferred embodiment the metal band is
coated using electroplating, preferably using a copper plated layer
and a tin plated layer, the coated metal being subsequently
annealed to produce a copper-tin alloy. The plating of layers of
metal such as copper, tin and nickel is known as such and provides
the desired layers on the strip.
[0032] According to still another preferred embodiment the metal
band is coated with a copper-tin alloy layer in a tin ion and
copper ion containing cyanide bath. The use of a copper ion and tin
ion containing bath is known as such and is a suitable way to coat
a metal strip with a copper-tin alloy coating.
[0033] The invention will be elucidated with the description of
three examples.
EXAMPLE I
[0034] Providing cold rolled strip (dimensions 0.35.times.500 mm in
cross-section); [0035] cleaning (2-3% alkaline cleaner, 1st step
dip cleaner, 2nd step electro-cleaner); [0036] cascade rinse with
brushes; [0037] activation (5% sulphuric acid); [0038] cascade
rinse; [0039] bronze plating (7% tin) electrolytically, with a
special cyanide bath, containing copper cyanide 30 to 40 g/l,
sodium cyanide 50 to 60 g/l (alternatively potassium cyanide 80 to
100 g/l), sodium stannate-3-hydrate 25 to 35 g/l, sodium carbonate
50 to 80 g/l, sodium hydroxide 10 to 15 g/l, organic compounds
(e.g. complex agents, grain refiner, wetter 0.5 to 1 g/l, etc.),
2.7 .mu.m coating thickness each side; [0040] cascade rinse plus
bronze anti-oxidising dip process (last rinse section, organic azol
derivate); slitting in accordance to customer specification.
EXAMPLE II
[0041] Providing cold rolled strip (dimensions 0.35.times.500 mm in
cross-section); [0042] cleaning (2-3% alkaline cleaner, 1st step
dip cleaner, 2nd step electro-cleaner); [0043] cascade rinse with
brushes; [0044] activation (5% sulphuric acid); [0045] cascade
rinse; [0046] bronze plating (7% tin) electrolytically, with a
special cyanide bath, containing copper cyanide 30 to 40 g/l,
sodium cyanide 50 to 60 g/l (alternatively potassium cyanide 80 to
100 g/l), sodium stannate-3-hydrate 25 to 35 g/l, sodium carbonate
50 to 80 g/l, sodium hydroxide 10 to 15 g/l, organic compounds
(e.g. complex agents, grain refiner, wefter 0.5 to 1 g/l, etc.),
2.7 .mu.m coating thickness each side; [0047] cascade rinse; batch
annealing under HNX atmosphere (5% hydrogen, 95% nitrogen) at
approx. 640.degree. C. for 12 hrs or continuous annealing under HNX
atmosphere at approx. 900.degree. C. for 1 min; [0048] brushing to
ensure active copper surface and the required finish; slitting in
accordance to customer specification.
EXAMPLE III
[0049] Providing cold rolled strip (dimensions 0.343.times.501 mm
in cross-section); [0050] cleaning (2-3 % alkaline cleaner, 1st
step dip cleaner, 2nd step electro-cleaner); [0051] cascade rinse
with brushes; [0052] activation (5% sulphuric acid); [0053] cascade
rinse; [0054] nickel plating electrolytically, with a standard
Watt's bath, containing nickel sulphate 200 to 250 g/l, sodium
chloride 20 to 40 g/l, boric acid 35 to 45 g/l, 1 .mu.m one side,
approx. <0.1 .mu.m other side; cascade rinsing; [0055] bronze
plating (7% tin) electrolytically, with a special cyanide bath,
containing copper cyanide 30 to 40 g/l, sodium cyanide 50 to 60 g/l
(alternatively potassium cyanide 80 to 100 g/l), sodium
stannate-3-hydrate 25 to 35 g/l, sodium carbonate 50 to 80 g/l,
sodium hydroxide 10 to 15 g/l, organic compounds (e.g. complex
agents, grain refiner, wetter 0.5 to 1 g/l, etc.), 3 .mu.m coating
thickness each side; [0056] cascade rinse plus bronze anti
oxidising dip process (last rinse section, organic azol derivate);
slitting in accordance to customer specification.
* * * * *