U.S. patent application number 09/810529 was filed with the patent office on 2001-10-18 for process for joining components made from case-hardened steel to components made from cast iron.
Invention is credited to Eulenstein, Tycho, Kern, Markus, Paasch, Rudolf, Schietinger, Bernd.
Application Number | 20010030224 09/810529 |
Document ID | / |
Family ID | 7635385 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010030224 |
Kind Code |
A1 |
Eulenstein, Tycho ; et
al. |
October 18, 2001 |
Process for joining components made from case-hardened steel to
components made from cast iron
Abstract
A process for joining or welding components made from
case-hardened steel to one another or to components made from cast
iron uses a nickel-containing filler. The components are not
prepared for the welding operation, i.e., the components do not
undergo at least partial abrasion of surfaces to be joined.
Inventors: |
Eulenstein, Tycho; (Kassel,
DE) ; Kern, Markus; (Filderstadt, DE) ;
Paasch, Rudolf; (Filderstadt, DE) ; Schietinger,
Bernd; (Esslingen, DE) |
Correspondence
Address: |
EVENSON, McKEOWN, EDWARDS & LENAHAN, P.L.L.C.
Suite 700
1200 G Street, N.W.
Washington
DC
20005
US
|
Family ID: |
7635385 |
Appl. No.: |
09/810529 |
Filed: |
March 19, 2001 |
Current U.S.
Class: |
228/246 ;
228/245 |
Current CPC
Class: |
B23K 2103/18 20180801;
F16H 2048/385 20130101; F16H 57/0025 20130101; B23K 2103/04
20180801; B23K 35/0255 20130101; B23K 2103/06 20180801; B23K 35/004
20130101; B23K 20/16 20130101 |
Class at
Publication: |
228/246 ;
228/245 |
International
Class: |
B23K 031/12 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 17, 2000 |
DE |
100 13 430.0-45 |
Claims
What is claimed is:
1. A process for joining components, comprising welding a first
component comprising case-hardened steel to a second component
comprising cast iron via a nickel-containing filler, wherein the
first and second components are welded together without undergoing
at least partial abrasion of surfaces to be joined.
2. A process according to claim 1, wherein the filler is in the
form of a foil.
3. A process according to claim 2, further comprising placing the
filler between the first component and the second component prior
to the welding, so that it is available over the entire area of the
joint which is to be welded.
4. A process according to claim 1, wherein the filler is
X10CrNiTi18 9.
5. A process according to claim 1, wherein the filler is pure
nickel.
6. A process according to claim 2, wherein a thickness of the foil
is from 0.1 to 0.3 mm.
Description
BACKGROUND AND SUMMARY OF INVENTION
[0001] This application claims the priority of German Application
No. 100 13 430.0, filed Mar. 17, 2000, the disclosure of which is
expressly incorporated by reference herein.
[0002] The present invention relates to a process for joining
components made from case-hardened steel to one another or to
components made from cast iron.
[0003] In modern production technology, it is of great interest to
join components made from case-hardened steel to one another or to
components made from cast iron. First, in terms of manufacturing
technology it is often more expedient to initially produce two
separate components and then to join them together. Second, the
demands imposed on the component to be produced often cannot be
fulfilled by one material.
[0004] By way of example, these problems arise in the automotive
sector during the production of transmissions, e.g., in a
differential gear the differential casing is produced from cast
iron, on account of its geometrically complicated configuration.
The ring gear connected thereto generally consists of case-hardened
steel, so that at its surface it has a high strength and is
wear-resistant, while having a relatively soft core material. The
term case-hardened steel is understood as meaning steels which have
a high surface hardness which is formed as a result of the
workpiece being annealed in carbon-dominating media followed by
quenching. As a result of the annealing operation, the surface
layer of the workpieces is enriched with carbon and is hardened by
a quenching operation from the annealing temperature.
[0005] In known differential gears, the connection between
differential casing and ring gear is produced by screws. A screw
connection has the drawback that a solid flange is required on the
differential casing. Construction space is required for this flange
and for the screw head and assembly. In addition, a minimum thread
depth is required to achieve a secure connection. Therefore, the
width of the ring gear must be able to accommodate the shank of the
screw. Furthermore, the dimensions of the ring gear must be
selected in such a way that it satisfies stability requirements, in
particular because the plane of loading from the forces to be
transmitted runs through the screw thread. These design boundary
conditions mean that the ring gear must be of a minimum size. This
minimum size, as well as the solid flange and the screw heads, have
an adverse effect on the weight of the differential gear and
therefore on production costs.
[0006] On account of the high carbon contents both in the cast iron
and on the surface of the case-hardened steel, it is not possible
to weld components of this type to one another. At the
concentrations which result with these combinations of materials,
the carbon in the molten material, during the rapid cooling after
welding, forms brittle microstructural constituents which have an
adverse effect on the quality of the weld seam and may lead to
cracks forming.
[0007] Although WO 99/58287 A1 has disclosed a process in which a
case-hardened ring gear is welded to a differential casing made
from cast iron with spheroidal graphite. To do this, the surfaces
which are to be welded on the otherwise fully machined components,
prior to welding, are at least partially abraded for weld
preparation, so that a narrow groove is formed where the welding is
to be carried out. This machining step means that in the
case-hardened ring gear the surface is removed in the region of the
joint. This is the region of the component which has the highest
carbon content. Since in a case-hardened steel the proportion of
carbon falls very considerably at increasing distance from the
surface, making the groove leads to an extreme reduction in the
carbon content at the joint, with the result that the
above-described problems involved in welding materials with high
carbon contents are reduced considerably. In the differential gear
described in WO 99/58287 A1, the welding is carried out with a
welding wire being supplied continuously.
[0008] A drawback of this process is that the parts which are to be
joined have to be prepared for the welding. The surfaces which are
to be welded are at least partially abraded. This preparation
represents an additional working step which, in the case of
case-hardened steel, is associated with high machining costs, on
account of the high strength.
[0009] In the known gear, the surfaces to be welded comprise two
regions: a groove region and a centering region which is arranged
beneath the groove region and at which the ring gear and
differential casing abut against one another. After the welding,
shrinkage processes cause this centering region to act as a notch
on the weld seam, which affects the quality of this seam.
[0010] Furthermore, the continuous supply of welding wire during
the welding operation represents a drawback, since this requires
complex positioning and control of the welding wire feed rate. In
the case of interference with these parameters, the filler is not
uniformly distributed over the entire height and length of the weld
seam. Particularly in the weld route, optimum mixing of the filler
with the molten metal is not ensured.
[0011] In view of this background, the present invention is based
on the object of providing a process for joining components made
from case-hardened steel to one another or to components made from
cast iron which is simple in terms of production technology and is
inexpensive.
[0012] According to the present invention, this object is achieved
by a process in which the components which are to be joined are
welded together using a nickel-containing filler without being
specially prepared for the welding operation (i.e. without at least
part of the joining surfaces which are to be welded being
abraded).
[0013] The process according to the present invention has the
advantage that no weld preparation, which is highly complex in
particular with case-hardened steels on account of the high
strength of the surface, is required. The components can be welded
together without any treatment of the joints, simply using a
nickel-containing filler, for example pure nickel or X10CrNiTi 18
9. In the solidified weld seam, the nickel of the filler forms a
buffer between the brittle microstructural constituents which form
when the molten material solidifies and thus prevents cracks from
forming in the weld seam. In this way, at least one machining step
is saved, thus simplifying production and therefore making it more
expedient. Particularly for series manufacture with high numbers,
this advantage makes its presence felt in terms of costs.
[0014] It has proven particularly advantageous to add the filler in
the form of a foil which is approximately 0.1 to 0.3 mm thick. This
foil is laid between the components to be joined prior to the
welding. The foil covers the entire area of the joint between the
components. A complex device for supplying filler in wire form
during welding is not required. Further, the filler is uniformly
available over the entire height and length of the joint, leading
to uniform mixing of the filler in the molten material and
therefore to a reproducible quality of the seam which is constant
over the height and length, in particular in the seam route.
[0015] Further, the exact position of the parts which are to be
welded with respect to one another can be determined by the
thickness of the foil. However, the presence of the filler which
determines the quality of the welded joint can also be monitored by
the position of the parts which are to be welded. In a preferred
embodiment, the foil additionally serves as a spacer between the
components which are to be joined, so that a gap is formed beneath
the weld seam after welding, with the result that the weld seam is
free of adverse effects from below (notch effects).
[0016] To achieve a high-quality weld seam, pure nickel has proven
to be a particularly appropriate filler.
[0017] Other objects, advantages and novel features of the present
invention will become apparent from the following detailed
description of the invention when considered in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 shows a section through a differential gear produced
using the process according to the present invention;
[0019] FIG. 2 shows a detailed illustration, in section, of the
connection point between ring gear and differential casing prior to
welding; and
[0020] FIG. 3 shows a detailed illustration, in section, of the
connection point between ring gear and differential casing after
welding.
DETAILED DESCRIPTION OF THE DRAWINGS
[0021] In accordance with FIG. 1, the differential gear 1 which has
been produced using the process according to the present invention
comprises a differential casing 2 made from cast iron with
spheroidal graphite and a ring gear 3 made from case-hardened
steel. The ring gear 3 is connected to a drive shaft via a drive
bevel wheel 4. The power generated by the engine is transmitted
from the drive shaft, via the differential gear 1, to two wheel
axles 6 and 7, which are of identical design. In the gear 1
according to the present invention, the differential casing 2 is
provided with a bearing shoulder 8. The bearing shoulder 8 is
integrally formed on the periphery 9 of the differential casing 2
onto which the ring gear 3 is pressed and, with respect to the axis
of symmetry 10 of the ring gear 3, extends beyond the periphery 9
of the differential casing 2 in the radial direction. It has a
rectangular cross section which is dimensioned to be sufficiently
narrow and short for it to be soft with respect to shrinkage of a
weld seam arranged on the bearing shoulder.
[0022] The ring gear 3 is pressed onto the differential casing 2 in
such a way that its side 11 which is remote from the toothing faces
towards the bearing shoulder 8. Before the ring gear 3 is pressed
on, a nickel-containing filler, in the form of an annular foil 12,
is pushed onto the differential casing 2, so that, as illustrated
in FIG. 2, after it has been pressed on the ring 12 comes to lie
between bearing shoulder 8 and ring gear 3. The ring 12 may serve
as a means for positioning the ring gear 3 on the casing 2. The
position of the ring gear 3 on the differential casing 2 can be
influenced and accurately determined by the thickness of the ring
12. To achieve a high-quality weld seam, pure nickel with a
thickness of 0.2 mm has proven to be a particularly advantageous
filler.
[0023] The internal diameter 13 of the foil 12 is larger than the
periphery 9 of the differential casing 2, so that a gap 14 is
formed beneath the ring 12, between bearing shoulder 8 and ring
gear 3. The external diameter 15 is exactly the same size as the
periphery 16 of the bearing shoulder 8. This geometric
configuration ensures that the filler is uniformly distributed over
the entire height and length of the joint and is optimally mixed
with the molten material in all regions during welding. The gap 14
ensures that the weld seam 16 is free of adverse effects from
below.
[0024] The use of the filler makes it possible for ring gear 3 and
differential casing 2 to be welded to one another despite the high
carbon content and without the components having to be prepared for
the welding operation. In the solidified weld seam 17, the nickel
in the filler forms a buffer between the brittle microstructural
constituents which are formed during cooling and therefore prevents
cracks from forming in the weld seam 17.
[0025] FIG. 3 shows a section through a differential gear 2 with a
ring gear 3 which have been welded together via the bearing
shoulder 8. The weld seam 17 is of wedge-shaped configuration and
is arranged with respect to the axis of symmetry 10 of the ring
gear 3.
[0026] The foregoing disclosure has been set forth merely to
illustrate the invention and is not intended to be limiting. Since
modifications of the disclosed embodiments incorporating the spirit
and substance of the invention may occur to persons skilled in the
art, the invention should be construed to include everything within
the scope of the appended claims and equivalents thereof.
* * * * *