JPH0825017B2 - Multi-layer overlay welding method for high hardness metal - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for producing an excellent wear resistant material by overlay welding a high hardness metal on the surface of a base material.

[0002]

2. Description of the Related Art In industry, many wear resistant materials are used in many machines and devices. The technology to be provided here is, for example, pulverization of coal for boilers for thermal power generation,
Cement clinker, rollers used for vertical mills used for crushing blast furnace slag, rollers, roller tires, table segments, hoppers, shoe liners, etc. All parts used for parts that are subject to severe wear due to contact with each raw material It is common to all members. These parts do not require wear resistance in all parts,
It suffices if only one side that comes into contact with the raw material has high wear resistance. Therefore, it is sufficient to build a multi-layer overlay of high-hardness metal only on the necessary wear-resistant surface, and if this part becomes worn during use, a new overlay weld is applied from above and a new as-new condition is applied. The wear resistant material can also be regenerated. Generally, since the area of the use surface that requires wear resistance is considerably large, it is required from the industrial profitability to perform welding efficiently whether it is the first buildup or the regenerated buildup after wear. Therefore, in general, CO ₂ welding method, MIG
Full-automatic welding methods such as welding method, submerged arc welding method and band arc welding method are widely adopted and are being widely used in various places.

[0003]

In order to form a wear resistant surface by overlay welding, it is natural that a weld metal having a higher hardness has a higher wear resistance. However, as is well known, the higher the hardness of the deposited metal is, the poorer the toughness is, and the biggest obstacle is that the under-bead crack easily occurs without being able to withstand the shrinkage stress during the multi-layer welding. This point is particularly remarkable in a material (base metal) which is generally considered to have poor weldability. As the hardness of the weld metal increases, the risk of under-bead cracking and peeling off of the weld overlay will increase. The hardness of the layer had to be limited to 600 or less in Hv. In addition, the thickness of the entire buildup layer must be limited to about 2 to 3 layers (6 to 10 mm),
There was a problem that the range provided with wear resistance remained thin.

In order to overcome this problem, various improvements have hitherto been made. For example, in order to prevent peeling and falling off, preheating is performed at 250 to 600 ° C before construction, and even during construction, the high interlaminar temperature is maintained to cover even the poor toughness, or immediately after welding, it is transferred to a furnace at 600 to 700 ° C. It may be charged and annealed to remove welding stress. However, it goes without saying that it is difficult to perform preheating at high temperature or welding under high temperature in actual work, and even if the stress is removed by annealing at high temperature, the high hardness of the build-up layer at the corner also decreases. is there. In addition, in order to solve the problem of this crack, a welding method of a so-called sandwich method, in which welding with a material having high hardness and welding with a material having excellent toughness are alternately repeated (JP-A-56-71)
No. 578), or a welding method in which welding cracks are positively generated in a portion having a small welding bead width by alternately changing the welding bead width in magnitude by changing the welding conditions in a constant time period (JP-A-2007-59). No. 60-12107), or a large number of grooves are formed on the surface of a base material, and a plurality of hard facings are laminated in a direction intersecting these grooves, and a bead is intentionally applied to a portion crossing the groove and the convex portion of the groove. It is possible to find out a welding method (Japanese Patent Laid-Open No. 174266/1985) which causes cracks in the wire.

It is recognized that any of the inventions is effective in solving the problem, but each problem still remains. That is, in the prior art cited at the beginning, since the layers excellent in abrasion resistance and the layers not excellent in abrasion are alternately accumulated, naturally, all layers accumulated the layers excellent in abrasion resistance. Wear resistance is low compared to the case. The second technique quoted is
Although it is a theoretically noteworthy invention, the pitch of increasing or decreasing the width of the weld bead is a problem in the current welding technology, and it is possible to avoid it from one crack (a portion with a small bead width). It is difficult to disperse small cracks by shortening the distance to the next crack (the next small bead width portion). For example, even if it is ideal to disperse the cracks at a pitch of 5 mm, it is difficult to actually carry out this ideal. Since the pitch is large, the opening of each crack is large, and the welding stress remains on the beads within the pitch. It is thought that there is a high risk that the beads will partly come off, and eventually the prevention action of the partial peeling and dropping of the beads becomes insufficient. The prior art cited at the end requires engraving a large number of fine grooves on the surface of a liner having a large area. This imposes a great burden, and it can be said that it is almost impossible to recover the wear resistance by repeating the same procedure for re-buildup after use.

In order to solve the above-mentioned problems, the present invention prevents a part of the build-up layer from peeling off due to under-bead cracks when performing multilayer build-up welding of high hardness metal. It is the first purpose. Next, the metal of this overlay layer is made of a material having a high hardness that greatly exceeds Hv600, which is the conventional practical limit, and the number of the overlay layers, which is the actual practical limit, is 2 to 3. Unlimited,
The purpose is to form an arbitrary wall thickness. Further, another object of this overlay welding is that neither preheating at a high temperature, maintaining a high interlayer temperature during welding, or high temperature stress relieving annealing after welding is unnecessary. Lastly, this welding method is not predicated on special processing, special skills, or complicated welding control means, and is versatile enough to be implemented even with a partial improvement of the popular welding machine. The purpose is to be.

[0007]

According to the method of multi-layer overlay welding of high hardness metal according to the present invention, when performing multi-layer overlay welding of high hardness metal on the surface of a base material,

[Equation 2] By limiting the heat input amount J calculated in the range of 2000 to 6000 J / cm and always limiting the interlayer temperature during welding to 300 ° C. or less, fine cracks orthogonal to the bead direction are formed in the bead of the weld metal. The above-mentioned problems have been solved by generating the particles evenly and in large numbers. Also, as a concrete welding type, the welding machine used is an open arc fully automatic welding machine, the wire used in this welding machine is a flux cored wire, and at this time the wire feed is up to 3000 cm. It is highly desirable to use a high speed wire feeder capable of up to / min. Furthermore, regarding the high-hardness metal to be built up, specifically, the hardness is such that Hv exceeds 600, and the number of built-up layers is not particularly limited, and it is required to build up multiple layers up to an arbitrary thickness, and to realize this. High hardness metal C: 3.0-7.0%
( Same as below by weight%) , Si: 0.5 to 2.0%, M
n: 0.5 to 4.0%, Cr: 20.0 to 35.0%,
The remaining Fe , or Mo, W, V, Zr, Ti,
B, Nb, Cd, Co, Al with one or more components selected from a maximum of 2.0% or C: 3.0-
7.0%, Si: 0.5 to 2.0%, Mn: 0.5 to
4.0%, V: 10.0 to 20.0%, W: 3.0 to 1
0.0%, Fe remaining , or Mo, Zr, Ti,
It is a very desirable mode that one or more components selected from B, Nb, Cd, Co and Al are added up to a maximum of 2.0%.

[0008]

The basic function of the present invention is to uniformly disperse a large number of fine cracks in the deposit in the direction perpendicular to the welding stress, thereby eliminating the stress around the cracks and virtually ignoring the residual stress on all beads. It is to reduce to the extent possible. Conventionally, the main reason why welding stress is a big problem is that the deposit of the welded part causes shrinkage stress as it cools and solidifies, but in the case of hardfacing welding, the material properties of the deposit and the base metal (for example, strength and hardness). , Toughness, etc.) are extremely large, and stress concentrates at the boundary between the two, resulting in large cracks that cause peeling off.
On the other hand, there have been many attempts as described above to intentionally disperse fine cracks evenly, but the present invention is to suppress the interlayer temperature during welding to 300 ° C. or less, This effect has been successfully achieved by a new technical idea of controlling J in the range of 2000 to 6000 J / cm, which is out of common sense from the completely conventional welding technology.

Regarding the interlayer temperature during welding, it is generally considered that higher temperature is more advantageous in the sense of compensating for the lack of toughness in order to suppress the generation of cracks. Therefore, preheating of high temperature and welding It has been a difficult procedure to maintain high temperature, and in that respect, it should be said that the idea is reversed. Regarding the heat input amount J during welding, the general rule is

(Equation 3) Although the heat input amount calculated in step 1 has a considerable difference due to the difference in welding method as illustrated in Table 1, in any case, a numerical value significantly different from the requirement (2000 to 6000 J / cm) of the present invention is usually used. To do.

[Table 1] The source is "Modern Welding Technology Series Vol.15, p. 67" (published by Kobo Publishing).

The reason why the heat input amount is limited to 2000 J / cm or more in the present invention is that if the heat input amount is less than that, melting of the metal by the arc is insufficient and overlay welding is practically impossible. Also, if the heat input exceeds 6000 J / cm, the thickness of each bead piled up increases and the gap between the cracks generated on the weld bead surface widens, so one crack is large and deep, and Residual stress increases in the beads between and cracks tend to grow, causing peeling and falling off, so this value was made the upper limit.
When the interlayer temperature exceeds 300 ° C, the rate of solidification of the pool of deposited metal becomes slow, the cracks on the weld bead surface become large and deep, and the number of cracks decreases, so the residual stress between cracks increases, so 300 ° C was set as the upper limit. .

In order to specifically carry out a welding method which is basically different from the concept of conventional welding technology, it is most desirable to apply the following welding equipment. First, an open arc type fully automatic welding machine is selected as the welding machine. The reason is mainly that it is simple in terms of construction, and since there is no need to add shielding gas or flux, the device is simplified and the entire device including auxiliary jigs (manipulator, positioner, etc.) is easy to construct and is portable. Can also be obtained. Therefore, this is a great advantage when the reclamation work of the wear resistant material is carried out on a business trip to an inconvenient site. Next, it is preferable to use a flux cord wire as the core wire used in the open arc type fully automatic welding. This wire is made by forming a strip-shaped thin steel plate into a pipe, and combining powdery alloy components, deoxidizers, gas generating components, etc. into its hollow to form a wire. It is extremely large and has a very high melting rate compared to solid wires. Furthermore, in order to comply with this feature, the wire feed device of the welding machine can feed the wire at a high speed of up to 3000 cm, which was about 600 cm per minute in the past, and it is a four-wheel drive high-speed wire feeder. It is desirable to adopt the model

By selecting a flux cored wire as the hardfacing component, the selection range of alloying elements is wide, and if necessary, the component and hardness most suited to the wear conditions can be obtained. Conventionally, the hardness of the hardfacing layer is maximum Hv
Although 600 and the built-up layers were only 2 to 3 layers and could be constructed only at a low level of 6 to 10 mm, in the present invention, Hv60 was obtained by performing the above welding conditions using the above welding equipment.
It was possible to form a high hardness overlay layer of 0 to 1000 to a desired thickness. Typical build-up welded components include C: 3.0 to 7.0%, Si: 0.5 to 2.0%,
Mn: 0.5-4.0%, Cr: 20.0-350
%, Residual Cr high Cr carbide-based material, or C: 3.
0-7.0%, Si: 0.5-2.0%, Mn: 0.5
-4.0%, V: 10.0-20.0%, W: 3.0-
A high V carbide-based material having 10.0% and remaining Fe can be mentioned. It should be noted that Mo, W, V, Zr, and T are appropriately added to these materials
Selecting one or more of i, B, Nb, Cd, Co, Al, etc., up to a maximum of 2.0% of additive components also produces more desirable results depending on the wear conditions. Generally, the welding materials used for hardfacing are mainly assembled by alloying elements that easily form carbides, and the carbides produced by each of these elements have extremely high hardness, and the hardness of the deposit obtained by overlay welding is It is said that it is almost proportional to the total amount of. Further, since the hardness of the deposit containing these alloy elements is generally in proportion to the amount of added carbon, a large amount of contained carbon such as C: 3.0 to 7.0% forms a hard layer having a high hardness. It is a factor that acts as the main function of forming.

The welding materials of high carbon and high alloy as described above have high crack susceptibility and the pitch of crack generation increases in proportion to the solidification rate, and the number of cracks decreases with slow cooling, resulting in large cracks. As a result, a small number will occur. The present invention restricts the heat input amount J during welding to an extremely low value, and as a result of high-speed welding at a low interlayer temperature, the solidification rate of the deposit becomes extremely high, and a large number of cracks are evenly dispersed, and the entire buildup layer is covered. It is based on the action of releasing a large amount of residual residual stress to prevent a large crack from peeling off.

[0014]

EXAMPLES Examples of the present invention are C: 6.0%, Cr: 2
Fe-based high-Cr carbide-based flux cored wire containing 7% and others with a diameter of 3.2 mm,
With the open arc automatic welding machine under the following welding conditions,
Overlay welding with a thickness of 30 mm was performed on a cylinder with a diameter of 900 mm manufactured from a high Cr carbide wear-resistant cast material. Welding conditions (1) Welding current 400Amp (2) Welding voltage 28V (3) Traveling speed 180cm / min (4) Interlayer temperature 300 ℃ max (5) Heat input 3700J / cm (6) No shield gas or preheating, afterheating Comparison Example 1 is a high Cr carbide wear-resistant cast material (C: 2.7%, Cr: 27%) used as the base material of the above-mentioned example,
Comparative Example 2 is a test material having a hardness of about Hv600 and hardened by a covered arc welding method, which is one of the conventional techniques. The rubber foil abrasion test method (RWAT) was tested under the same conditions for the above-mentioned Example and Comparative Examples 1 and 2. Table 2 shows the test conditions, and Table 3 shows the test results.

[0015]

[Table 2]

[0016]

[Table 3]

As can be seen from Table 3, the examples of the present invention exemplify that they have approximately twice or more the abrasion resistance of the hardfacing layers of the prior art. FIG. 1 is a diagram showing the positions for showing the micro and macro structures of this embodiment, and FIG. 2 is a microphotograph of the AA cross section in FIG. 1, in which needle-shaped carbides grow in the same direction. ing. Further, FIG. 3 is a microphotograph of the BB cross section in FIG. 1, in which needle-shaped carbides are grown at a high density. FIG. 4 is a macrophotograph of the metal structure of another embodiment, which was built up on a vertical roller with a thickness of about 30 mm and put into practical use.
After that, fine cracks are distributed almost evenly.

[0018]

By the multi-layer overlay welding method of a high hardness metal according to the present invention, it is possible to obtain a thick overlay layer having a hardness higher than those obtained by the overlay welding methods conventionally used for the same purpose. The wear resistance and its service life are dramatically improved. Moreover, since the welding speed of the construction is extremely high, the work efficiency is excellent, the welding machine is simplified and the portability is high, and the regeneration construction can be easily carried out on a business trip. further,
Since this welding method is a method of stacking several layers of high-hardness weld metal on a high-hardness weld metal, the base metal to be built up by applying this technique is a mild steel material with good weldability. However, it is possible to easily perform regenerative restoration by hardfacing welding even for a high-carbide-based casting material (for example, hard cast iron) generally used as a wear-resistant material.

[Brief description of drawings]

FIG. 1 is a front view showing a position where a micrograph of a metal structure is taken in an example of the present invention.

FIG. 2 is a photomicrograph showing the metal structure of the AA cross section in FIG.

FIG. 3 is a micrograph showing a metal structure of a BB cross section in FIG.

FIG. 4 is a macro photograph showing a metal structure of another example.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area // B23K 103: 02

Claims (9)

[Claims] 1. A method of applying multi-layer overlay welding of a high hardness metal onto a surface of a base material, wherein: The heat input amount J calculated by the method is limited to the range of 2000 to 6000 J / cm, and the interlayer temperature during welding is always limited to 300 ° C. or less to form fine cracks in the bead of the weld metal at right angles to the bead direction. A method for multi-layer overlay welding of high-hardness metal, which is characterized by uniformly and dispersively generating. 2. The multilayer build-up welding method for high hardness metal according to claim 1, which is an open arc fully automatic welding method. 3. The multilayer build-up welding method for high hardness metal according to claim 2, wherein the wire used is a flux cored wire. 4. The method of multilayer build-up welding of high-hardness metal according to claim 3, wherein a high-speed wire feeder capable of feeding a wire up to 3000 cm / min is used. 5. The high hardness metal according to claim 1, wherein the hardness of the high hardness metal to be built up is at least Hv of more than 600, and the number of the built up layers is not particularly limited, and multi-layered up to an arbitrary thickness. Multilayer overlay welding method. 6. The high-hardness metal to be built up according to claim 5, wherein C: 3.0 to 7.0% ( weight% or less is the same ), S.
i: 0.5 to 2.0%, Mn: 0.5 to 4.0%, C
r: 20.0 to 35.0%, the balance being Fe . 7. The high-hardness metal to be built up according to claim 5, wherein C: 3.0 to 7.0% (the same applies in% by weight or less ) and S.
i: 0.5 to 2.0%, Mn: 0.5 to 4.0%, V:
10.0 to 20.0%, W: 3.0 to 10.0%, the rest
A multi-layer overlay welding method for a high hardness metal, which is Fe . 8. The method according to claim 6, further comprising adding M to the component.
o, W, V, Zr, Ti, B, Nb, Cd, Co, Al
Up to 2.0% by weight of one or more ingredients selected from
Multi-layer overlay welding method for high hardness metals characterized by addition
Law. 9. The method of claim 7, further comprising adding M to the component.
o, Zr, Ti, B, Nb, Cd, Co, Al
Add up to 2.0% by weight of one or more selected ingredients
A multi-layer overlay welding method for high hardness metal, which is characterized in that