JPH05337648A - Underlaying welding method for medium and high carbon steel wheel - Google Patents

Abstract

PURPOSE:To provide the welding method capable of effectively preventing hot cracking of root pass weld metal in cladding by welding of the medium and high carbon steel wheel. CONSTITUTION:In the cladding method by welding for the medium and high carbon steel wheel, a flux-cored wire containing at least 0.8-5.0% Nb for the total weight of the wire is used, the curvature R of a collar/a wheel tread corner part (c) before welding is made to >=5mm, the wire (d) is held in the vertical direction at 200-450 deg.C between preheating and passing and in a state with the wire lead distance (L) made to 15mm<=L<=30mm in the opposite direction to the direction of rotation o f the wheel, underlaying welding is performed by submerged arc welding. This welding method is suitable for cladding by welding of the medium and high carbon steel wheel of a crane traveling wheel, a reclaimer wheel, a railroad wheel, etc., of an ironworks.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to overlay welding, and particularly to overlay welding of traveling wheels of cranes and reclaimers of steelworks, wheels of medium and high carbon steel such as railway wheels by submerged arc welding. The present invention relates to a suitable underlay welding method.

[0002]

2. Description of the Related Art When a reclaimer wheel, a railway wheel or the like is used for a certain period of time, the tread portion or the collar portion may be thinned due to wear, or the collar portion may be deformed in some cases. Therefore, it is used after being repaired and recycled by overlay welding. These wheels include JIS G 5101 SC45 and JI
A base metal with various C contents such as S E 5401 is used, and when repairing, a method of directly overlaying a hardfacing welding material that obtains hardness similar to that of the base metal tread surface depending on the C content of the base metal. One of the methods is to first carry out underlay welding using a mild steel-based or low alloy-based welding material, and then carry out overlay welding using a welding material with which a predetermined hardness is obtained.
As a welding method, submerged arc welding is widely applied to both the underlay welding and the overlay welding.

[0003]

There are two types of wheels, one of which is a brim type and the other of which is a double brim type. Also in this case, there was a problem that cracks were likely to occur in the weld metal at the brim / tread surface corners. Cracks were easily affected by the dilution of the base metal, and moreover, there was a strong tendency for cracks to occur easily in the first-layer weld metal, which is subject to a high restraining force because part of the weld metal hangs on the brim.

In particular, high temperature cracking is likely to occur in a wheel containing 0.3% or more of C, and in particular, when the C content of the base metal wheel is as high as about 0.7% as in JIS E5401, the weld metal The C content also increased to about 0.3%, and it was difficult to completely prevent cracking, so the reliability for overlay repair was not sufficient. In particular, high temperature cracks are likely to occur in the first layer weld metal at the brim / tread surface corner portion, and it is characterized in that it continuously occurs in the circumferential direction of the wheel. Further, also in the welding of the tread, there is a problem that when the dilution ratio of the base metal is high, the C content of the weld metal of the first layer becomes high and hot cracking occurs similarly to the brim / tread corner. The overlay weld metal may come off during use of the overlay welded wheel, and the wheel may become unusable.This is due to fatigue and the cracks occurring in the first layer weld metal as described above may also progress. Contribute.

Also in terms of construction, there is a close relationship between the cracks occurring in the first layer weld metal and the preheating / pass temperature, and a wheel containing a C content of about 0.7% has a low preheating of about 150 ° C. -There was a problem that cold cracking occurred when welding at the temperature between passes. Further, if the preheating / pass temperature is too high, the above-mentioned high temperature cracking is promoted, resulting in a serious obstacle to the overlay repair work of the wheel.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a welding method capable of effectively preventing hot cracking of the first layer weld metal in overlay welding of medium / high carbon steel wheels. Is to

[0007]

[Means for Solving the Problems] In order to prevent hot cracking of the weld metal in the first layer of medium and high carbon steel wheels, it is premised that the restraint by the collar and the dilution of the base metal to some extent occur as described above. It is necessary to establish construction technology that does not cause hot cracking.

From the above viewpoints, the inventors of the present invention have made earnest studies on a construction technique for preventing hot cracking, and as a result, have found that the pre-welding shape of the collar / tread corner of the wheel and the tendency of hot cracking to occur. It has been found to be closely related to.

That is, FIG. 1 shows a general pre-welding shape of a double brim type wheel. In the figure, a is a brim, b is a tread, and c is a brim / tread corner. First, prior to underlay welding, the diameter of the tread surface is reduced by machining in order to remove the portion that has been damaged during use, such as wear and peeling, and the collar portion is also machined according to the degree of damage. Done. Then, a corner portion having a certain curvature is formed, and if this curvature is small, hot cracking is likely to occur.

Further, the preheating / pass temperature is also related to high temperature cracking, and if the preheating / pass temperature is too high, the hot cracking susceptibility becomes high and the base metal dilution ratio is known, as is generally known. And the hot cracking is further promoted by the increase in the C content of the first layer weld metal. Further, there is a wire aiming position as a factor affecting the base metal dilution rate during welding, and it is preferable to perform welding in a state where the molten pool is slightly ahead in order to reduce the base material dilution rate as much as possible.

The present inventors properly control these factors, and further, by using a specific flux-cored wire,
It has been found that it is possible to prevent high-temperature cracking that tends to occur in the weld metal of the first layer due to submerged arc welding of the brim / tread surface corner of the wheel.

That is, the present invention is a method for overlay welding of medium / high carbon steel wheels, in which a flux-cored wire containing at least Nb: 0.8 to 5.0% based on the total weight of the wire is used and before welding. Curvature R of the brim / tread corner is set to 5 mm or more, and preheating / pass temperature 200 to 450 ° C
Hold the wire in the vertical direction and set the wire lead distance (L) in the direction opposite to the wheel rotation direction by 15 mm ≦ L ≦
The gist is a build-up welding method for medium / high carbon steel wheels, which is characterized by performing submerged welding by submerged arc welding in a state of 30 mm.

The present invention will be described in more detail below.

[0014]

[Action]

Corner curvature : In a double brim type wheel, welding is carried out while holding the wire d perpendicular to the tread surface b as shown in FIG. In this case, since the fillet welding aiming at the corner cannot be performed at the corner portion c, the shape of the bead f tends to be slightly concave at the center portion of the bead as shown in FIG. However, the corner curvature R is 5 mm
In the above cases, it was found that hot cracking can be prevented.

Wire holding angle and lead distance : In order to prevent hot cracking, the dilution of the base material should be reduced as much as possible. For this purpose, the angle of the wire should be vertical and the molten pool should be slightly advanced. Is the best. For that purpose, it has been found that the holding angle of the wire is set to the vertical direction and the wire lead distance L is set to 15 mm ≦ L ≦ 30 mm. The wire lead distance is closely related to the bead shape, the base metal dilution rate, and the arc stability.
If it is less than mm, the dilution rate of the base material becomes high, and the weld metal has a convex shape. If it exceeds 30 mm, the molten pool is markedly advanced, the arc becomes unstable, and the risk of welding defects such as defective fusion increases.
Although FIG. 4 shows the target position of the wire d in the plan view of the wheel, the wire lead distance L is clockwise from the position A at 0 o'clock (12 o'clock) in the figure at the corner portion c (opposite to the rotation direction). Direction) to the wire aiming position B.

Preheating / interpass temperature : As described above, preheating
If the interpass temperature is less than 200 ° C., cold cracking easily occurs in the weld metal or the base metal due to the constraint of the base metal wheel. Again 45
If the temperature exceeds 0 ° C, hot cracking of the weld metal, particularly hot cracking of the weld metal at the corners, tends to occur, and at the same time, the risk of liquefaction cracking in the heat-affected zone increases. For this reason, the preheating / pass temperature is set to 200 to 450 ° C.

Flux-cored wire : The reason why the flux-cored wire is used in the present invention is that the dilution rate of the base material can be suppressed to be lower than that of the solid wire. However, it is essential that the flux-cored wire contains at least 0.8 to 5.0% of Nb with respect to the total weight of the wire. Nb has a strong affinity with C and easily forms NbC.
In the first layer welding of medium-high carbon steel wheels containing about 0.3 to 0.7% of C, niobium carbide is formed during solidification of the weld metal to reduce the adverse effect of C on hot cracking. If the amount of Nb is less than 0.8%, the effect cannot be obtained, and if it exceeds 5.0%, the effect is saturated and the peeling of the slag is deteriorated.

The flux-cored wire may be appropriately added with one or more alloy components such as Cr, W, Mo and V in order to maintain the hardness of the weld metal. However, excessive addition causes a marked increase in hardness and may cause cold cracking during welding. Therefore, it is desirable to suppress the content to 1% or less in each case. Further, there is no problem in adding deoxidizing agents such as Si and Mn. Further, various fluorides and oxides may be added to improve workability such as slag removability.

Underlay welding is carried out by submerged arc welding as in the conventional case. It goes without saying that the conditions other than the above are not particularly limited.

Next, examples of the present invention will be described.

[0022]

EXAMPLE This example is an example applied to the repair overlay of a double brim type wheel used in an iron mill.

[Table 1] For the wheel made of the base material with the chemical composition shown in Fig. 2,

[Table 2] Using the flux-cored wire with the chemical composition shown in

[Table 3] as well as

[Table 4] Under weld welding was carried out by submerged arc welding under the conditions shown in, and further overlay welding was performed. After the completion of welding, the presence or absence of cracks was investigated by a liquid penetration flaw detection test while cutting the outer peripheral surface in stages. The results are also shown in Table 4.

As shown in Table 4, no welding defects were recognized in any of the examples of the present invention. On the other hand, in the comparative example, when the curvature of the brim / tread corner is small (Comparative Example 8) or the preheating / pass temperature is high (Comparative Example 7), the Nb amount of the flux-cored wire for underlay welding is further increased. If low
In all cases, such as (Comparative Examples 5 and 6), hot cracking occurred in the underlay weld metal.

[0024]

As described in detail above, according to the present invention,
In overlay welding of medium / high carbon steel wheels, it is possible to completely prevent high temperature cracking of the underlay weld metal, which could not be prevented by conventional techniques.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view showing a general pre-welding shape of a double brim type wheel.

FIG. 2 is an explanatory diagram showing a wire holding angle.

FIG. 3 is a view showing a bead shape of a collar / tread surface corner portion obtained by conventional underlay welding.

FIG. 4 is a plan view illustrating a target position of a wire.

[Explanation of symbols] a collar b tread surface c collar / tread surface corner portion d wire e welding tip f bead g tangent line

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location B23K 35/368 E 7362-4E (72) Inventor Shogo Natsume 100 Miyako, Urakawachi, Fujisawa City, Kanagawa Prefecture -1 Stock Company Kobe Steel Works, Fujisawa Works (72) Inventor Yoshizo Hashimoto Miyazawa Fujimae, Kanagawa Prefectural back Kawauchi 100-1 Stock Company Kobe Steel Works, Fujisawa Works (72) Inventor Shigeki Nishiyama Miyazawa Fujisawa, Kanagawa Prefecture Urakawachi 100-1 Stock Company Kobe Steel Works Fujisawa Works

Claims (1)

[Claims] 1. In the overlay welding method for medium / high carbon steel wheels, at least Nb: 0.8-5.
A flux-cored wire containing 0% is used, and the curvature R of the collar / tread surface corner before welding is set to 5 mm or more,
Pre-heating / pass-pass temperature 200-450 ° C, the wire is held in the vertical direction, and the wire lead distance (L) is set in the direction opposite to the wheel rotation direction so that 15mm ≦ L ≦ 30mm. Overlay welding method for medium / high carbon steel wheels characterized by arc welding for underlay welding.