JPH06106381A - Filler metal for welding sintered material - Google Patents

Abstract

PURPOSE:To provide the filler metal for welding sintered materials which can weld the sintered material and the sintered material (or steel products with high strength, enables welding with high-energy density beams and has excellent reliability and productivity. CONSTITUTION:The component compsn. to the total weight of the filler metal consists of 0.05-0.5wt.% C, 0.1-1.5wt.% Si, 0.2-2.5wt.% Mn, 0.1-2wt.% total of one or two kinds of Al and Ti, 2-5wt.% B and the balance Fe and inevitable impurities. The filler metal for welding the sintered material has a wire form and is used for electron beam welding or laser welding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for automobile parts, home electric appliance parts, OA equipment parts and the like, and is used for welding iron-based sintered materials to each other or when welding together iron-based sintered materials and steel materials. It relates to a filler material for binder welding.

[0002]

2. Description of the Related Art Joining of steel materials is widely performed by general arc welding or high energy density beam welding such as electron beam welding and laser welding. However, since the sintered material is porous, when this sintered material is welded by these methods, the holes of the base material gather and large blow holes are formed in the weld metal, ensuring the strength of the welded part. become unable. Therefore, conventionally, as a method of joining sintered materials,
There are (1) brazing method, (2) shrink fitting method, (3) infiltration method, and (4) high energy density beam welding using a high Mn-based filler material.

[0003]

However, all of these methods have the following drawbacks. (1) Method by brazing In this method, selection of brazing material and brazing conditions are difficult, and if the wettability of the brazing material is too good, the brazing material is absorbed in the pores of the base metal and There is a shortcoming that there will be a shortage.
On the other hand, if the brazing material has poor wettability, good joining cannot be achieved. In addition, oxide adheres to the surface of the sintered material,
If it penetrates inside, brazing is extremely difficult. Furthermore, since local heating is difficult and the cooling rate is generally slow, when brazing is performed after quenching, the base metal softens and the original strength of the material cannot be exhibited.

(2) Method similar to shrink fit This method uses the difference in linear expansion coefficient of two members to join at the time of sintering, or to join by shrink fit or cold fit after sintering. However, the joint strength of the joints produced by such a method tends to deteriorate with age depending on the use environment.

(3) Method by infiltration This is a method in which an infiltrant such as copper is set in the vicinity of the joint between two members and the infiltrant is melted to fill the pores of the joint with molten metal. Since the bonding strength depends on the infiltrant, the strength of the bonded portion is significantly lower than that of the base material. Further, as described above, it is difficult to join a sintered material having an oxide attached or permeated on the surface or inside thereof. Further, in this method, although the sintered materials can be joined to each other, it is basically impossible to join different materials of the steel material and the sintered material.

(4) Method for high energy density beam welding using high Mn filler metal The present inventors have already proposed a method for performing high energy density beam welding using this high Mn filler metal. (Patent application No. 56198 of 1991). According to this method, defects such as cracks and blowholes can be prevented, and a welded part having good strength can be obtained. However, as described above, this method prevents blowhole defects for sintered materials that have oxides attached and permeated to the surface or inside, or sintered materials that have moisture and oils attached. Difficult to do.

As described above, none of the conventional welding and joining methods and filler materials have been proposed so far as they satisfy all requirements in terms of prevention of defects and strength of the joint. In particular, it is difficult to prevent blowhole defects in a sintered material in which an oxide is attached and permeated on the surface or inside and a sintered material in which moisture or oil is attached and absorbed.

Therefore, if the above-mentioned high energy density beam welding can be applied to the joining of the sintered materials or between the sintered material and the steel material, it is advantageous in terms of penetration depth, strength, productivity and strain. it is conceivable that. On the other hand, a sintered part may intentionally cause oxides to adhere to and penetrate the surface or inside of the sintered material in order to improve the properties of the material. In addition, due to the manufacturing process, fats and oils may adhere and permeate to the surface or inside of the sintered material, or water may adhere and absorb depending on the use environment. Even for such a sintered material, there is a demand for development of a joining technique capable of preventing blowhole defects and the like, in particular, a filler material.

The present invention has been made in view of the above problems, and in particular, even a porous sintered material in which oxides, oils and fats are adhered and permeated on the surface or inside,
It is possible to weld and join sintered materials or steel materials with high strength,
It is another object of the present invention to provide a filler metal for welding a sintered material, which enables high energy density beam welding and has excellent reliability and productivity.

[0010]

A filler material for welding a sintered material according to the present invention is a sintered material welding material used for welding and joining together iron-based sintered materials or an iron-based sintered material and a steel material. The composition of the filler metal for the total weight of the filler metal is C: 0.05 to 0.5
% By weight, Si; 0.1 to 1.5% by weight, Mn; 0.2 to 2.5% by weight, Al and Ti; 0.1 to 2% by weight in total of at least one kind, B; 2 to 5% by weight, balance: Fe and unavoidable impurities Is characterized in that.

[0011]

In order to solve the above-mentioned problems, the inventors of the present invention have found that, as a result of intensive studies, by controlling the composition of the filler metal to a predetermined value, there is a remarkable improvement effect on the joining quality. The present invention has been completed.

That is, the present invention provides a filler material used for welding and joining iron-based sintered materials to each other or an iron-based sintered material and a steel material, and particularly to an oxide on the surface or inside. Provided is a filler material suitable for use in welding and joining a sintered material to which oil, fat, water or the like has adhered and penetrated. In the present invention, the composition of the filler with respect to the total weight of the filler is regulated within the following range, and preferably the shape of the filler is formed into a wire shape, and this filler is used during high energy density beam welding.

C; 0.05 to 0.5% by weight Si; 0.1 to 1.5% by weight Mn; 0.2 to 2.5% by weight Al and Ti; 0.1 or 2% by weight of one or two in total B; 2 to 5% by weight balance; Fe and inevitable impurities.

The use of such a filler material having a component composition during high energy density beam welding has a remarkable effect particularly in preventing the occurrence of blowhole defects.

Iron-based sintered materials used as machine parts are
The true density is in the range of 6.4 to about 7.2, and the true density of iron is about
Since it is 7.85, it means that the iron-based sintered material has pores in the true density smaller than that of iron. Oxygen and nitrogen existing in the holes generate CO gas and N ₂ gas during welding, and the generated gas causes blowhole defects in the weld metal.

In this case, if the ideal sintered material, that is, the surface and the inside are not adhered and permeated with oxides, fats or water, or the degree of adhered permeation is extremely small, the above-mentioned high Mn- By using an Al—Ti based filler material (Japanese Patent Application No. 3-56198), various defects such as blow holes can be prevented.

However, since the amount of generated gas increases remarkably in the sintered material which has been subjected to the oxidation treatment and the sintered material to which oil or water is attached and penetrated, deoxidation or denitrification by Mn, Al and Ti. Then, it is difficult to diffuse or fix the gas outside the weld metal.

Therefore, in the present invention, a large amount of B,
In addition, by adding an appropriate amount, deoxidation is performed and the generated gas is diffused outside the weld metal. That is, B is an element which is generally said to have a deoxidizing effect. However, according to the study by the present inventors, B has an effect of easily releasing the generated gas to the outside of the weld metal in addition to this deoxidizing effect. It was confirmed that there was. It is speculated that this is because the addition of B contributed to the decrease in the solidification temperature of the weld metal and the decrease in the surface tension of the weld metal.

Next, the reason for adding the components and the reason for limiting the composition of the filler material for welding a sintered material according to the present invention will be explained.

C: 0.05 to 0.5 wt% Sintered materials used as ordinary equipment parts contain about 0.4 wt% or more of C in order to improve strength. In the case of high energy density beam welding, since the ratio of melting the base metal is high, C of the base metal reacts with oxygen existing in the periphery, and CO
Generates gas. Since it is preferable to suppress the amount of this gas generated to the necessary minimum, the C content of the filler material should be low. In particular, the sinter that has been subjected to the oxidation treatment and the sinter that has oil and fat or water attached and permeated have a significantly large amount of generated gas, so the C content of the filler metal is 0.5% by weight.
If it exceeds, it becomes difficult to prevent the generation of blow holes. On the other hand, the practical production of a filler metal having a C content of less than 0.05% by weight raises the cost and saturates the effect of suppressing the generated gas. Therefore, C
The proper content of is 0.05 to 0.5% by weight.

Si: 0.1 to 1.5 wt% Si is effective as a deoxidizing agent and can be expected to have the effect of reducing the viscosity of the weld metal. However, if Si is added excessively, the toughness of the weld metal deteriorates. Therefore, S
The proper content of i is 0.1 to 1.5% by weight.

Mn: 0.2 to 2.5 wt% Mn is effective as a strong deoxidizing agent, but if it is added in a large amount, it will be the most important addition in the present invention, as will be explained in the aspect of the filler material described later. Since the room for adding the element B is narrowed, the appropriate content of Mn is 0.2 to 2.5% by weight.

Al and Ti; a total amount of at least one of 0.
1 to 2% by weight These elements are strong deoxidizers and have an effect on nitrogen absorption. In order to obtain this effect, it is necessary to add one or two of these elements in a total amount of 0.1% by weight or more. However, even if one or two of these elements are added in a total amount of more than 2% by weight, the effect is saturated.
Therefore, the proper addition amount is 0.1 to 2% by weight in total.

B: 2 to 5% by weight As described above, it is an important additional element in the present invention,
In addition to the deoxidizing effect, it has the effect of lowering the solidification temperature of the weld metal contact and the surface tension of the molten metal, and thus exerts a remarkable effect in preventing blowholes. This effect of preventing blowholes is obtained by adding 2% by weight or more of B.

On the other hand, when B is added in an amount of more than 5% by weight,
The ductility of the weld metal deteriorates significantly, and cracks easily occur. Therefore, the proper addition amount of B is 2 to 5% by weight.

Since iron-based sintered materials generally contain about 0.4% by weight or more of C in order to improve strength, low temperature cracking is likely to occur. Therefore, it is preferable to reduce the hardness and lower the range of hydrogen by preheating and postheating during welding.

Mode of Filler Material As the filler material used at the time of high energy density beam welding, what is called a wire-like material is preferable. However, it is difficult to melt, cast, and draw a wire having the composition defined in the present invention due to the workability problem. Therefore, it is preferable to produce a predetermined filler wire by forming a so-called flux cored wire by enclosing the metal powder in the sheath.

In this case, the constraint condition is the ratio of the flux (here, metal powder) to the total weight of the wire. A wire having a weight ratio of the flux (metal powder) of more than 40% may be broken during wire drawing or may not be encapsulated, which makes it difficult to manufacture. Therefore, the ratio (weight ratio) of the flux (metal powder) to the weight of the entire wire is preferably 40% or less.

The element B, which is a feature of the present invention, is preferably added in the form of Fe-B in terms of manufacturing cost.

The wire diameter is preferably 0.8 to 1.6 mm. By drawing the wire so that the wire diameter falls within this range, the work during welding becomes smooth, which is preferable in terms of welding work.

[0031]

EXAMPLES Examples of the present invention will be described below.

Example 1 A sintered material having a chemical composition and density shown in Table 1 below (thickness: 1.2 mm
X width 20 mm x length 100 mm), so-called steam treatment (550
Hold in steam for 2 hours). Laser welding was performed on the steam-treated welding base metal under the conditions shown in Table 2 below while supplying filler materials having various component compositions. The filler material used was a wire having a diameter of 1.2 mm, and its composition is shown in Table 3 below.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

After welding, the presence or absence of blowholes and cracks was examined by X-ray inspection and cross-section inspection of the welded portion. The results are also shown in Table 3.

As shown in Table 3, it can be understood that defects can be prevented by using the filler material having the component composition range of the present invention.

Example 2 The sintered base material used in Example 1 and a mild steel material SS41 (thickness 12
mm × width 20 mm × length 100 mm), but the interface was laser welded. The filler material used has the composition of No. 16 in Table 3, and the welding conditions are the same as those shown in Table 2. After welding, in the same manner as in Example 1, the presence or absence of defects was examined, and no defects were found, and a sound weld was obtained.

Example 3 A sintered material having a chemical composition and density shown in Table 1 (thickness 12 mm × width 20)
mm × 100 mm length), after quenching oil is impregnated, laser welding is performed under the conditions shown in Table 2 while supplying the filler metal with various component compositions to the base metal deoiled with trichloroethane. did. The filler material used was a wire with a diameter of 1.2 mm, and its composition is shown in Table 4.

[0040]

[Table 4]

After welding, the presence or absence of defects was examined in the same manner as in Example 1. The results are also shown in Table 4. Even if deoiled with trichloroethane, it cannot be completely deoiled, so the wire of the comparative example cannot prevent the defect, but by using the filler material in the composition range of the present invention, the defect can be prevented. confirmed.

Example 4 A sintered material having a chemical composition and density shown in Table 1 (thickness 12 mm × width 20)
mm × length 100 mm) was left in an environment of 30 ° C.-80% for 1 month, and laser-welded to the moisture-absorbed base material under the conditions shown in Table 2. The filler material having the composition of No. 12 in Table 3 was used, and after welding, the presence or absence of defects was examined in the same manner as in Example 1. As a result, no defects were observed and a sound weld was obtained.

As described above, by using the filler material in the composition range of the present invention, a sound weld portion can be formed even with respect to the sintered material in which oxides and oils or moisture adhere to the surface or inside. Was obtained.

[0044]

EFFECTS OF THE INVENTION According to the present invention, even a porous sintered part, particularly a sintered material in which oxides, fats and oils or water adhere to and penetrate the surface or inside thereof, has not been obtained conventionally. Since a high-energy-density beam welding can be performed while obtaining a large welded portion, it is possible to provide a joining technique having high productivity as well as reliability.

Claims (2)

[Claims] 1. A filler material for welding a sintered material, which is used for welding and joining iron-based sintered materials to each other or to an iron-based sintered material and a steel material, wherein the component composition with respect to the total weight of the filler material is C; 0.05-0.
5% by weight, Si; 0.1 to 1.5% by weight, Mn; 0.2 to 2.5% by weight, Al and Ti; 0.1 or 2% by weight in total of one or two, B; 2 to 5% by weight, balance: Fe and A filler metal for welding a sintered material, which is an unavoidable impurity. 2. The filler metal for welding a sintered material according to claim 1, which has a wire shape and is used for electron beam welding or laser welding.