BRAZING - Vacuum brazing technology for high
bonding strength joints of metal carbide parts on metallic holders
TEHNOPROF - Excellence Research Center for Advanced Surface
Processing by Plasma and Vacuum Technologies
Funding agency: RELANSIN, S1, Project no. 712 /12.09.2000.
Coordinator: National Institute for RD in Optoelectronics INOE 2000
Project Leader: Dr. Viorel Braic
Partner: SC
GEVALCO INDUSTRIAL SRL
Project responsible: Eng. Valeriu Rosca
The goal of the project is to
look into ways to strengthen the mechanical bond between steel holders of
various cutting and milling tools and cemented tungsten carbides under varied
vacuum brazing conditions. These conditions include carbide quality, type of
brazing alloy, temperature, and length of brazing process.
Melted filler metal, called the
braze alloy, flows into the joint during the brazing process, which is a
joining technique commonly used on metals (but sometimes used on ceramics).
The mechanism of brazing is based
on the ability of the filler metals to dissolve elements of the bulk material
thus creating a strong metallurgical bond. The characteristics of those bonds
depend on the combination of filler metal and bulk material. As an example, for
stainless steel parts, brazed with nickel base filler metals, the achieved
metallurgical bond is similar to a welded joint. In contrast to welding,
melting of the base materials does not take place due to the melting ranges of
the filler metals, which are located significantly below those of the base
materials.
The filler and parent materials
must be metallurgically compatible in order to create a sound brazed junction.
Additionally, the joint design must have a gap that allows capillary action to
pull or disperse the molten braze filler. Numerous variables, such as the
brazing environment and the makeup of the base material and braze alloy, affect
the necessary joint gap.
Because of its versatility and
the high integrity that can be achieved in the joints it creates, brazing is a
well-recognized and commercially utilized procedure for combining dissimilar
metals in a variety of sectors. Because of its dependability in both critical
and non-critical applications, this joining method is among the most popular
ones.
The advantage of the vacuum
brazing process vs. classical brazing is due to the fact that in the
vacuum furnace the whole part is heated to brazing temperature. Thereby
distortion, which occurs by using local heating methods like flame-brazing or
induction-brazing, can be avoided. Furthermore, parts with a complex joint
design can be brazed.
Specific objectives:
- Implementing
the vacuum brazing technology in production
- Improvement of the technical and
qualitative standards of the final products
-
An increase in the number of effective technologies added to
domestic production lines
-
Reduction of production costs through the application of newly
developed vacuum brazing technology
-
Increased productivity of the final products
-
Extension of the products' lifespan
Results:
v Every set
of materials that needed to be brazed had a different brazing alloy.
v NiB is the ideal brazing alloy for K20 carbide types, but Cu brazing
alloy yielded the greatest results for P30 and G30 carbide kinds;
v All types
of carbides, steels, and alloys utilized demonstrated a direct proportionality
between the observed unitary shear force and the brazed area;
v Regardless
of the type of carbide and nature of the brazing alloy, OLC 45 steel type
yields the greatest results for shear force, with a value that is consistently
greater when compared to other steel types;
v The
vacuum brazed pieces exhibited a stronger resistance in the unitary shear force
test for every combination of steel holder type and cemented carbide;
v The
outcomes appear to be connected to cleaning the brazed region and the necessity
of unneeded additional procedures following the brazing, such as those
involving flame and even induction brazing techniques.
THE INFLUENCE OF THE BRAZING ALLOY NATURE AND CARBIDE
TYPE G30, K20 and P30 carbide brazed on OL37, OL 60 and OLC 45 Unitary shear forces for carbides brazed with Cu alloy
Papers published and presented at
national and international conferences
Surface processing by unconventional methods: coatings by cathodic
arc technique and vacuum brazing, V.Braic,
G.Pavelescu, M.Braic, M.Balaceanu, National Relansin Programme - Excellence
in Projects, 2002, pp. 126-131
Vacuum brazing technology for cutting tools production made by
cemented carbide and steel holders. V.Braic, M.Braic, M.Balaceanu,
Unconventional Technologies Review, No.2, p.92-96, 2003
Quality improvement of the tools made by cemented carbide active
parts brazed on steel holders, V. Braic, M. Balaceanu,
M. Braic, I. Tudor, A. Popescu, 2nd International Conference ²Research and development
in mechanical industry² RaDMI 2002, 02 - 04. September 2002, Vrnjačka
Banja, Yugoslavia
Vacuum brazing technology – a modern technology for increasing the
life time of tools, V. Braic, I. Tudor, M. Braic, M. Balaceanu,
A. Popescu, IXth International Conference
of the Romanian Association of Nonconventional Technologies, Sibiu, 2003