CN103801858A - Welding rod for spot welding electrode surface electric spark cladding TiB2-TiC multiphase coating and its preparation method - Google Patents

Abstract

The preparation method of the welding rod for spot welding electrode surface electric spark welding TiB ₂ -TiC multiphase coating of the present invention contains 60~80% (Ti powder+B ₄ C powder+C powder) (wherein Ti powder occupies 74.8%, B ₄ C powder occupies 18.5%, C powder occupies 6.7%) or contains 60~80% (TiB ₂ powder + TiC powder) (of which TiB ₂ powder occupies (30-60)%, TiC powder occupies (40- 70)%), (18~35)% Ni powder, (0.5~5)% Mo powder, (0.5-2)% W powder. Using the TiB ₂ -TiC cladding rod of the present invention adopts the surface electric spark cladding technology to obtain a continuous, uniform and dense TiB ₂ -TiC multiphase coating on the surface of the spot welding electrode. The coating has stable performance and simple cladding process . TiB ₂ -TiC cladding rod of the present invention obtains TiB ₂ -TiC multiphase coating after adopting spot welding electrode surface electric spark cladding process, can not only effectively improve the service life and anti-adhesion of spot welding electrode, compare TiB ₂ , The TiC single-phase coating electrode has a long service life, and the TiB ₂ -TiC multi-phase coating obtained by electric discharge on the surface of the spot welding electrode of the present invention has simple process, superior comprehensive performance and strong use value.

Description

Welding rod for spot welding electrode surface electric spark cladding TiB2-TiC multiphase coating and its preparation method

technical field

The invention relates to the processing technology of metal surface coating, especially the surface coating processing technology of spot welding electrodes .

Background technique

In recent years, with the increase of automobile output, especially the increasing proportion of cars in the total output, people have put forward higher requirements for the quality of automobiles. Among them, how to prolong its service life and maintain a good appearance quality is an important indicator, and the corrosion resistance of the car is an important factor affecting the service life of the car. Based on the above requirements, the traditional cold-rolled steel sheets can no longer meet the needs in this regard. Galvanized steel sheet has excellent anti-corrosion properties, so it is more and more widely used in the fields of automobiles, home appliances, construction, etc., especially in the automobile manufacturing industry to replace cold-rolled steel sheets and is widely used. In the automobile production industry, resistance welding is the main form of connection for such steel plates. According to statistics, there are about 4,000 to 6,000 resistance spot welding spots on each car body. For example, in the body-in-white assembly of Shanghai Volkswagen Passat, The total number of welding points per vehicle reaches 5892 points, and the average life of each spot welding electrode is about 500~2500 points. Spot welding electrodes are the most commonly used consumables in automobile body welding, and the procurement cost of the most used electrode caps is generally RMB 5-20 per pair. About 100 pairs need to be replaced. Based on the current domestic production of automobiles, it is estimated that the annual electrode investment will reach hundreds of millions of yuan. Not only that, but when spot welding galvanized steel sheets, the plastic deformation of the electrodes is relatively fast and the service life is also short, resulting in the need for frequent trimming and replacement of the electrodes, resulting in a decrease in production efficiency and an increase in production costs. Therefore, improving the life of electrodes is one of the important issues that need to be solved urgently in the field of automobile manufacturing. This is of great significance for improving spot welding quality, ensuring body assembly quality, controlling body errors, reducing production costs, and improving work efficiency. the

During the spot welding process, the diameter of the electrode head generally increases with the increase of the electrode use time. The increase in the diameter of the electrode head will lead to a decrease in the current density during spot welding and a decrease in the diameter (or strength) of the formed welding spot, thus Lead to the failure of the spot welding electrode. Due to the working characteristics of spot welding electrodes, especially when welding galvanized steel sheets, there are roughly the following ways of failure: plastic deformation, denudation, alloying, pitting and self-healing, recrystallization, thermal fatigue, etc. In general, the above seven failure mechanisms are caused by the combination of high temperature and pressure. the

Factors that affect the service life of spot welding electrodes include electrode material, electrode geometry, surface condition of the electrode head, and welding specifications. The most potential for improving the service life of electrodes is to study spot welding electrode materials (including the development of new spot welding electrode alloys and composite materials for spot welding electrodes) and surface treatment of electrode heads, among which the surface treatment of spot welding electrodes is the most developed. potential. Since the surface of the electrode head is mainly subjected to force, heat and metallurgical action in the spot welding process, the surface treatment of the electrode head should be the most economical and effective way to improve the service life of the electrode. The main coating methods for spot welding electrode surface treatment are electric spark deposition and physical vapor deposition. Gobez deposited cobalt, tantalum, nickel, TiN and molybdenum on the CrZrCu electrode of spot welding galvanized steel respectively. The results showed that the first three coatings reduced the life of the electrode and the latter two coatings slightly increased the wear resistance of the electrode. Studdon of the University of Wollongong used TiN coated electrodes to spot weld Zn-Al coated steel. The welding current was 10-20% lower than that of uncoated electrodes, and the electrode life was longer than that of uncoated electrodes. The surface life of spot welding electrodes with CrN electrodes is relatively stable, changing around ±7%, while the surface life of spot welding electrodes coated with CrN electrodes changes around ±40%. The reason for the large fluctuation is that there are many defects in the CrN coating. The patent owned by Huys Industries Limited of Canada reports the process of surfacing TiC layer on the surface of spot welding electrode. When this type of electrode is used for micro-spot welding nickel-plated steel plate and nickel plate, its electrode life reaches 1200 points, which is twice that of CuCrZr electrode. , the main reason for improving the life of the electrode is that the TiC coating on the surface hinders the local welding between the electrode and the nickel-plated plate and also reduces the plastic deformation of the electrode. In addition, the TiC layer on the electrode surface can also improve the anti-adhesion performance of the electrode The electrode life of this kind of spherical electrode reaches more than 1000 points when spot welding galvanized steel sheets for automobiles, which is 2.5 times that of CuCrZr electrodes. The main reason for providing electrode life is that the TiC coating delays and prevents the diffusion of Zn, delays Alloying with electrode base copper. Compared with TiC, TiB ₂ is superior to TiC in terms of electrical conductivity, melting point, and hardness, and is also an ideal electrode surface cladding material. In order to obtain a TiB ₂ coating on the surface of the spot welding electrode, Luo Cheng et al. have done a lot of work on this. It was found that to obtain an ideal _TiB2 coating, a transition layer must be deposited on the electrode surface first, which makes the welding process of the electrode complicated, and greatly reduces the efficiency of electrode welding, which is not conducive to large-scale Promotional use. TiB ₂ —TiC composite ceramic material has the characteristics of high melting point, high hardness, high thermal conductivity, low expansion coefficient, high wear resistance and good electrical conductivity, and compared with single-phase TiB ₂ , TiB ₂ —TiC composite ceramic The wettability between the material and the spot welding electrode matrix is good, and it can be deposited directly on the surface of the spot welding electrode without an intermediate layer.

Chinese patent CN200410060704.4 discloses a welding rod for spot welding electrode surface electric spark cladding coating and its preparation method. In this patent, the main component of the welding rod is TiB ₂ . Chinese patent CN101775513A discloses a method for preparing TiB ₂ -TiC dispersion-strengthened copper-based composite material by mechanical alloying. Although the Chinese patent "Metal Surface Welding Coating, Especially Gradient Coating Method CN 01115197.8" can also obtain TiB ₂ -TiC coating, because this patent is to use Fe-based or Co-based or Ni-based powders to add ceramics and then use The spraying method is fixed on the surface of the workpiece and then scanned by plasma to obtain the coating. The conductivity of the coating obtained by this method cannot meet the conductive requirements of the spot welding electrode surface, so it cannot be used for the surface treatment of the spot welding electrode, and the process is much more complicated than the present invention. many. Although the patent "TiC/TiB _2- based cermet composite strengthening method on the surface of the roll (CN 102628867 A) can also obtain TiB ₂ -TiC coating, because the patent uses a nickel-based alloy on the surface of the workpiece, and then on the nickel-based The surface of the alloy (40-50% TiB ₂ , 30-40%TiC, 10-15%Mo, 0.5-1.5%Cr, the balance is Fe) ceramic electrodes are obtained by electric spark welding to obtain TiC/TiB ₂ layers, Because the coating contains Fe, the electrical conductivity of the coating obtained by this method cannot meet the surface conduction requirements of the spot welding electrode so it cannot be used for the surface treatment of the spot welding electrode, and the process is much more complicated than the present invention.

Contents of the invention

Aiming at the problems existing in the prior art, the present invention provides a cladding material with low cost, good electrical conductivity, good thermal conductivity, good wettability with the substrate, and high melting point - electric spark cladding TiB ₂ on the surface of the spot welding electrode - a welding rod for TiC multiphase coating and its preparation method .

The present invention relates to a welding rod for electric spark welding TiB ₂ -TiC ₂ coating on the surface of spot welding _electrodes . Powder, C powder, Ni powder, Mo powder, W powder as raw materials, 60~80% by weight (Ti+B ₄ C+C) powder (of which Ti powder accounts for 74.8%, B ₄ C powder accounts for 18.5%, C powder occupies 6.7%), 18~35% Ni powder, 0.5~5% Mo powder, 0.5-2% W powder are evenly mixed;

Or use TiB ₂ powder, TiC powder, Ni powder, Ni powder, Mo powder, W powder with a particle size of 100-200 mesh and a purity greater than 99% as raw materials, with a weight percentage of 60-80% (TiB ₂ +TiC) Powder (of which TiB ₂ powder occupies (30-60)%, TiC powder occupies (40-70%)), 18-35% Ni powder, 0.5-5% Mo powder, 0.5-2% W powder and mix evenly ;

It is prepared by mechanical alloying and vacuum semi-sintering.

The TiB ₂ -TiC2 composite coating is produced in situ during the EDM welding process of the welding rod prepared by Ti powder, B ₄ C powder, C powder, etc., and its coating performance is better than that of TiB ₂ powder directly. The coating performance of the welding rod prepared by powder such as + TiC powder is better.

A method for preparing a welding rod for electric spark welding TiB ₂ -TiC _{2 coating} on the surface of a spot welding electrode. , C powder, Ni powder, Mo powder, and W powder as raw materials, with 60~80% by weight (Ti+B ₄ C+C) powder (of which Ti powder accounts for 74.8%, B ₄ C powder accounts for 18.5%, and C powder accounts for 18.5%. Powder accounts for 6.7%), 18~35% Ni powder, 0.5~5% Mo powder, 0.5-2% W powder are evenly mixed;

Or use TiB ₂ powder, TiC powder, Ni powder, Ni powder, Mo powder, W powder with a particle size of 100-200 mesh and a purity greater than 99% as raw materials, and TiB ₂ powder + TiC powder with a weight percentage of 60-80% (In which TiB ₂ powder occupies (30-60)%, TiC powder occupies (40-70%)), 18-35% Ni powder, 0.5-5% Mo powder, 0.5-2% W powder are evenly mixed;

Put steel balls and mixed powder with a ball-to-material ratio of 10:1~50:1 into a ball mill tank in a glove box filled with argon, so that the ball-material mixture accounts for 50~75% of the inner cavity volume of the spherical tank; at room temperature Under the high-energy ball milling at a speed of 300-500 rpm for 24-48 hours; then add 2-10% of the total weight of the above-mentioned mixed powder to the ball-milled powder and press it into the required rod, and the rod is placed in a vacuum furnace It is sintered at a temperature range of 900°C to 1150°C in an argon protective atmosphere to prepare a cladding rod that can meet the needs of cladding TiB ₂ -TiC.

The invention adopts mechanical alloying and vacuum semi-sintering process to prepare electric spark welding TiB ₂ -TiC multiphase coating welding rod, which has the advantages of simple process and low production cost; not only that, the prepared TiB ₂ -TiC welding rod, It makes up for the low conductivity of TiC single-phase cladding rod, poor wettability between _TiB2 single-phase cladding rod and spot welding electrode substrate, and complex multi-layer cladding process.

Below, the experimental data of examples illustrate the performance of the TiB ₂ -TiC coating that the TiB ₂ -TiC multiphase cladding rod of the present invention adopts the electric spark cladding process to obtain on the surface of the spot welding electrode in the form of a chart, and compared with the traditional TiB _2. Comparing the properties of TiB _{2 and} TiC coatings obtained by EDM deposition process on the surface of spot welding electrodes with TiC single-phase cladding rods.

Table 1 is the composition list of six kinds of TiB ₂ -TiC welding rods and single-phase TiC and TiB ₂ welding rods. The compositions in the table are all weight percentages. The relevant information of the coated electrode obtained under the welding process (voltage 24V, capacitance 30000μF, substrate speed 1200r/min, vibration frequency 50Hz and welding time 120s). As can be seen from Table 1, the coated electrodes obtained in Examples 1 to 6 of the present invention have better coating continuity than TiB ₂ single-phase cladding rods, and the obtained coated electrodes do not have obvious substrate exposure; The conductivity of the coated electrode is higher than that of the coated electrode obtained with the deposited rod.

Table 1

Table 2 is a comparison of the service life of the coated electrodes obtained by the spot welding thickness of 0.8mm galvanized steel sheets between Examples 1-6 of the present invention and single-phase TiB ₂ , TiC cladding rods on the surface of the spot welding electrodes using the electric spark cladding process. It can be seen from the table that the service life of the TiB ₂ -TiC composite coating obtained by welding the electrode surface with examples 1 to 6 of the present invention is comparable to that of the TiB, TiC coating obtained by welding the single-phase TiB ₂ and TiC welding rod on the electrode surface. TiC coating has a long service life and is suitable for the connection of spot welding galvanized steel sheets in the machinery industry.

Table 2

Description of drawings

Fig. 1 is the XRD of Example 1 of the present invention after welding the powder, the welding rod after semi-sintering, and the coating after EDM welding. Fig. 2 is the metallographic picture of the TiB ₂ -TiC composite phase coating and the TiB ₂ -TiC composite coating electrode obtained by using the TiB ₂ -TiC welding rod in the spot welding electrode surface of the present invention through the electric spark deposition process picture of the exterior.

Detailed ways

Example 1: 72 grams of (Ti+B ₄ C+C) powder (of which Ti powder occupies 74.8%, B ₄ C powder occupies 18.5%, C powder occupies 6.7%), 25 grams of Ni powder, 2 grams of Mo powder After 1 gram of W powder is evenly mixed, it is ball milled at room temperature for 30 hours at a speed of 400 rpm in an argon ball mill tank full of argon with a ball-to-material ratio of 35:1. The viscose is pressed into the required rods, and the rods are sintered in a vacuum sintering furnace at 900°C in an argon protective atmosphere and then used for electric spark cladding on the surface of spot welding electrodes.

Example 2: 74 grams of (Ti+B ₄ C+C) powder (of which Ti powder accounts for 74.8%, B ₄ C powder accounts for 18.5%, C powder accounts for 6.7%), 22 grams of Ni powder, 3 grams of Mo powder, 1 gram of W powder, uniformly mixed, ball milled for 33 hours at a speed of 400 rpm at room temperature in an argon ball mill tank filled with ball-to-material ratio of 30:1, and added 5 grams of viscose to the ball-milled above-mentioned mixed powder Pressed into the required rods, the rods are sintered in a vacuum sintering furnace at 950°C in an argon protective atmosphere, and then used for spot welding electrode surface electric spark cladding.

Example 3: 76 grams of (Ti+B ₄ C+C) powder (where Ti powder accounts for 74.8%, B ₄ C powder accounts for 18.5%, C powder accounts for 6.7%), 21 grams of Ni powder, 2 grams of Mo powder, 1 gram of W powder, uniformly mixed, ball milled at room temperature for 36 hours at a speed of 400 rpm in an argon ball mill tank filled with a ball-to-material ratio of 35:1, and added 5 grams of viscose to the ball-milled above-mentioned mixed powder Pressed into the required rods, the rods are sintered in a vacuum sintering furnace at 1000°C in an argon protective atmosphere, and then used for spot welding electrode surface electric spark cladding.

Example 4: 75 grams of (Ti+B ₄ C+C) powder (of which Ti powder accounts for 74.8%, B ₄ C powder accounts for 18.5%, C powder accounts for 6.7%), 21 grams of Ni powder, 3 grams of Mo powder, 1 gram of W powder, uniformly mixed, ball milled at room temperature for 39 hours at a speed of 400 rpm in an argon ball mill tank filled with a ball-to-material ratio of 35:1, and added 5 grams of viscose to the ball-milled above-mentioned mixed powder Pressed into the required rods, the rods are sintered in a vacuum sintering furnace at 1050°C in an argon protective atmosphere, and then used for spot welding electrode surface electric spark cladding.

Example 5: 33.5 grams of TiB ₂ powder, 38.5 grams of TiC powder, 25 grams of Ni powder, 2 grams of Mo powder, and 1 gram of W powder were uniformly mixed in an argon ball mill tank filled with a ball-to-material ratio of 40:1 at room temperature Under ball milling at a speed of 400 rpm for 40 hours, the above-mentioned mixed powder that has been ball-milled and 8 grams of viscose are pressed into required rods. After sintering at ℃, it is used for electric spark cladding on the surface of spot welding electrodes.

Example 6: 35 grams of TiB ₂ powder , 39 grams of TiC powder, 22 grams of Ni powder, 3 grams of Mo powder, 1 gram of W powder, after being uniformly mixed, are filled with an argon ball mill tank with a ball-to-material ratio of 40:1 at room temperature Under ball milling at a speed of 400 rpm for 38 hours, the above-mentioned mixed powder that has been ball-milled and 8 grams of viscose are pressed into the required rods. After sintering at ℃, it is used for electric spark cladding on the surface of spot welding electrodes.

As shown in the accompanying drawings: Fig. 1 is the XRD of the welded rod powder, the semi-sintered welded rod, and the coating after EDM welding in Example 1 of the present invention. Fig. 2 is the metallographic picture of the TiB ₂ -TiC composite phase coating and the TiB ₂ -TiC composite coating electrode obtained by using the TiB ₂ -TiC welding rod in the spot welding electrode surface of the present invention through the electric spark deposition process picture of the exterior.

Claims (2)

1. The welding rod used for spot welding electrode surface electric spark welding TiB ₂ -TiC ₂ coating is characterized in that: Ti powder, B 4 C powder, B ₄ C powder, C powder, Ni powder, Mo powder, W powder as raw materials, Ti+B ₄ C+C powder with a weight percentage of 60~80%, of which Ti powder accounts for 74.8%, B ₄ C powder accounts for 18.5%, and C powder accounts for 6.7% %, 18~35% Ni powder, 0.5~5% Mo powder, 0.5-2% W powder are evenly mixed; Or use TiB ₂ powder, TiC powder, Ni powder, Ni powder, Mo powder, W powder with a particle size of 100-200 mesh and a purity greater than 99% as raw materials, and TiB ₂ powder + TiC powder with a weight percentage of 60-80% , wherein TiB ₂ powder occupies 30-60%, TiC powder occupies 40-70%, 18-35% Ni powder, 0.5-5% Mo powder, 0.5-2% W powder are uniformly mixed; It is prepared by mechanical alloying and vacuum semi-sintering. 2. The welding rod used for spot welding electrode surface electric spark welding TiB ₂ -TiC ₂ coating is characterized in that: Ti powder, B 4 C powder, B ₄ C powder, C powder, Ni powder, Mo powder, W powder as raw materials, Ti+B ₄ C+C powder with a weight percentage of 60~80%, of which Ti powder accounts for 74.8%, B ₄ C powder accounts for 18.5%, and C powder accounts for 6.7% %, 18~35% Ni powder, 0.5~5% Mo powder, 0.5-2% W powder are evenly mixed; Or use TiB ₂ powder, TiC powder, Ni powder, Ni powder, Mo powder, W powder with a particle size of 100-200 mesh and a purity greater than 99% as raw materials, and TiB ₂ powder + TiC powder with a weight percentage of 60-80% , wherein TiB ₂ powder occupies 30-60%, TiC powder occupies 40-70%, 18-35% Ni powder, 0.5-5% Mo powder, 0.5-2% W powder are evenly mixed; Put steel balls and mixed powder with a ball-to-material ratio of 10:1~50:1 into a ball mill tank in a glove box filled with argon, so that the ball-material mixture accounts for 50~75% of the inner cavity volume of the spherical tank; at room temperature Under the high-energy ball milling at a speed of 300-500 rpm for 24-48 hours; then add 2-10% of the total weight of the above-mentioned mixed powder to the ball-milled powder and press it into the required rod, and the rod is placed in a vacuum furnace It is sintered at a temperature range of 900°C to 1150°C in an argon protective atmosphere to prepare a cladding rod that can meet the needs of cladding TiB ₂ -TiC.

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