JPS5913952B2 - Covered arc welding rod for surface hardfacing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coated arc welding rod for surface hardfacing, and in particular to metal parts that are exposed to contact pressure during processing, such as the die face surface of a processing mold or the shoulder radius of a bead. Wear and seizure of the mold,
The present invention relates to a coated arc welding rod for surface hardening overlay, which is suitable for use in overlay welding of areas where occurrence of galling scratches and the like is noticeable.

For example, press working, which is a typical mass production method used in automobile manufacturing, is a low-speed plastic process with high contact pressure.
Abrasion of the mold, seizure of the mold and panel, or scratches on the panel that occur during processing reduce the dimensional accuracy and surface quality of the manufactured product, and rework requires a huge amount of man-hours.
This significantly hinders the improvement of various production goals such as high processability, product uniformity, and economical use of materials.

Cast iron is generally used as the material for conventional press molds10, so in order to eliminate the above-mentioned problems, some kind of surface treatment must be applied to improve wear resistance and galling resistance (seizure resistance). things are being done.

One example is a coating method such as hard Cr plating, but this method has the disadvantage that the coating layer tends to peel off during processing. In order to prevent this drawback, a surface coating method by welding has been adopted, and various welding materials are commercially available, but all of these are welding materials for hardfacing iron-based surfaces, which are called hard facing materials. , welding cracks are likely to occur when welding cast iron materials, and galling scratches are noticeable during press working, so it cannot be used without a lubricant, and furthermore, as the galling scratches progress, This was extremely unsatisfactory since wear of the overlay welding area was also accelerated. On the other hand, there is also a nickel-based welding material called a welding material for cast iron that is relatively excellent for overlay welding on cast iron materials, but in this case, unlike the hard facing materials mentioned above, lubrication is not perfect. 30, which can be used with almost no scratches even when the weld metal is used, has poor wear resistance due to the low hardness of the weld metal, which can cause wrinkles on the product panel and reduced dimensional accuracy. However, the mold life was short and efficiency was reduced.

The purpose of the present invention is to eliminate the above-mentioned conventional drawbacks35.In particular, it is an object of the present invention to provide a scale that can be easily overlay welded to pressed cast iron materials, has excellent wear resistance, and is lubricated. An object of the present invention is to provide a coated arc welding rod for surface hardfacing that can obtain a special weld metal that does not cause galling scratches even without a chemical agent.

The coated arc welding rod for surface hardfacing of the present invention has a Ni or Fe-Ni core wire with Si: 5 to 13 as an alloying agent.
%, B: 1-5%, Nb: 0.4-4%, C: 1-6%
It is characterized by being coated with a coating material containing ordinary arc stabilizers such as carbonates and fluorides, slag forming agents, gas generating agents, etc. In one embodiment, welded welded Is the metal composition the weight? So, Ni: 40
% or more, Si: 3-8%, B: 0.1-0.5%, Nb
C: 0.3 to 2%, C: 0.2 to 1.5%, and the balance is Fe and inevitable impurities.

In order to eliminate the drawbacks of the prior art as described above, the present inventors have conducted various tests and research, and have found that the composition of the deposited metal obtained by covered arc welding is more preferably weight-heavy. So, Si: 3-8%, B: 0.1-0.5%, Nb:
0.3-2%, C: 0.2-1, 5? , Ni4O% or more, the balance is Fe, and a small amount of unavoidable impurities makes it possible not only to obtain a weld metal with excellent hardness and wear resistance, but also to produce a press plated with this weld metal. It was confirmed that galling caused by seizure does not occur during sliding contact between the die and the steel plate as the workpiece, even without the use of lubricating oil. Therefore, by using a coated arc welding rod for surface hardfacing that can obtain such a weld metal composition, it is possible to achieve the above-mentioned special properties required for press working and to achieve even better results. It becomes possible to obtain an overlay welded part that also has excellent wear resistance and galling resistance.

The reasons for limiting the above-mentioned preferred weld metal composition range (wt%) will be described below.

First, Ni is an essential element in order to prevent seizure and galling phenomena due to its excellent sliding properties during sliding contact with the steel plate during press working.
If it is less than 0%, the occurrence of scratches becomes noticeable, so 40% or more is required.

Si is an element that mainly forms a compound with Ni and Fe and contributes to improving the hardness of the weld metal, but if it is less than 3%, its effect is negligible and the wear resistance is insufficient.

On the other hand, if the content exceeds 8%, the hardness will further increase, but the effect on wear resistance will not improve dramatically, and on the contrary, the weld metal will become brittle and cause cracking, so the upper limit is A value of 8% is desirable. B increases the hardness even at a content of about 0.1% in the weld metal and is effective in improving wear resistance, and this effect becomes even more pronounced due to the presence of C.

However, if the content exceeds 0.5%, the deposited metal becomes brittle and causes cracking, and machining conditions after overlay welding become poor, so the upper limit was set at 0.5%. N
b makes the weld metal composition finer and significantly reduces cracking susceptibility.

The effect becomes noticeable from about 0.3%, but if the content exceeds 2%, compounds with N1 and B increase, and the hardness of the weld metal exceeds Hv38O, making it brittle. This is not preferable as it may cause cracking.
C forms a solid solution in the matrix or combines with Nb and B to form carbide, contributing to improving wear resistance. This effect becomes more noticeable when the content exceeds 0.2%, but when the content exceeds 1.5%, the amount of carbide produced increases, and the edges of the carbide damage the panel surface, which is the workpiece, during press processing. The content was set to 1.5% or less to avoid the negative effects of attaching. As detailed above, each alloying element increases the hardness of the weld metal within its content range, and functions to prevent mold wear, seizure, and galling during press processing. . In particular, the addition of Nb makes it possible to deposit a high-hardness weld metal composition onto any desired part of the mold by coated arc welding easily and without causing weld cracks. Therefore, in a coated arc welding rod for surface hardfacing to obtain the above-mentioned weld metal composition,
The core wire may be a so-called pure Nl core wire consisting of 95% or more Ni and unavoidable impurities, or a so-called pure Nl core wire consisting of 50 to 60% Ni and the balance Fe.
A so-called Fe-Ni core wire containing unavoidable impurities is used, and the coating includes Si: 5-13% as an alloying agent, B
: 1 to 5%, Nb: 0.4 to 4%, C: 1 to 6%, and other ordinary arc stabilizers such as carbonates and fluorides, slag forming agents, gas generating agents, etc. are used. It is desirable to coat the core wire with this coating material.

At this time, the coating material is applied to the core wire at a coverage rate of 3 by weight.
It is preferable to cover it so that it is about 0 to 50%. Also,
The amount of alloying agent added in the above coating material was determined as a result of various experiments.
It was determined so as to obtain the above-mentioned weld metal composition while considering the yield during welding, and will be explained in more detail below.

First, by adding 5% or more of Sl to the coating material,
Increases the hardness of weld metal and contributes to improved wear resistance.

Further, by adding Si, the flowability of the molten metal is improved, and the bead appearance becomes beautiful. However, 1
If it exceeds 3%, the deposited metal becomes brittle and weld cracks occur, which is not preferable. Next, by adding B and Nb to the coating material in an amount of 1 to 5% and 0.4 to 4%, respectively, the composition range in the weld metal described above can be obtained. Although it causes weld cracking, when the amount added is within the above-mentioned range, no particular adverse effect is observed in terms of welding work.

C is an alloying agent and at the same time a strong deoxidizing agent, and 1%
If the addition amount is less than that, blowholes and pits will occur significantly, making it impossible to obtain a normal weld bead.

Additionally, if it is added in excess of 6%, carbides with B, Nb, etc. will increase, reducing the galling resistance of the weld metal and at the same time weakening the blowing force of the welding arc. The transition to the material side tends to become discontinuous, and as a result, it is not possible to obtain a continuous and beautiful bead appearance, and this is undesirable because it causes slag burning and reduces welding work.Furthermore, the above-mentioned alloying agents are not included in the coating material. In addition, it contains calcium carbonate, barium carbonate, fluorite, mica, etc., which function as ordinary arc stabilizers, slag forming agents, gas generating agents, etc.

Of these, mica is added as a lubricant when coating the welding rod core wire with a coating material. Note that in the above example, Ni
Although Si, B, Nb, C, etc. other than the above are all added from the coating material, the effect remains the same even if some of them are alloyed into the core wire.

However, if one component is added to the core wire, it becomes difficult to draw the wire, which may lead to poor production quality and an increase in cost. Example 1 The compounding ratio of the coating material and the chemical composition of the core wire used in the coated arc welding rod for surface hardfacing according to the present invention and the reference coated arc welding rod used during development are shown in Tables 1 and 2, respectively. .

In addition, among the coating material compounding ratios shown in Table 1, Fe is an element contained because Si, B, Nb, etc. are added in the form of ferroalloy, and when Ni% in the weld metal is 40%.
%, the function of the present invention will not be hindered.

Therefore, an appropriate amount of water glass was added to the coating material shown in Table 1, and the surface of the pure Ni core wire shown in Table 2 was coated with the coating material by normal means to create a welding rod, and each welding Overlay welding was performed using a rod at an alternating current of 95 to 100 A, and each performance was evaluated.

The results are shown in Tables 3 and 4. In the above table f, ◎ indicates extremely good, ◯, 1△ indicates slightly poor, and X indicates poor.

Table 3 shows the chemical composition of the weld metal by the above welding rod,
Table 4 shows the evaluation of the test results for the hardness of the deposited metal, welding conditions, abrasion resistance, galling resistance, etc.

Furthermore, in Tables 3 and 4, conventional Ni-based and Fe-based overlay welding materials for cast iron, which are commercially available, were similarly evaluated for comparison. As a result, the welding rod of the present invention shows better results than the reference welding rod and Ni-based or Fe-based welding materials. In particular, as is clear from Tables 3 and 4, by adding Si, B, Nb, etc. to the Ni-based welding material, it is possible to improve the wear resistance to a large extent without impairing the galling resistance. Became a master. Example
2 In order to further clarify the effect of Nb addition in Example 1, the Nb content in the weld metal was determined based on the coating composition ratio of welding rod Taki 1 shown in Table 1 of Example 1. The effects on hardness and weld cracking were investigated.

That is, Sill%, B2%, C3%, and mica 5% in the coating were kept constant, and the amount of Nb was varied between 3% and 5%, and as the amount of Nb added changed, carbonate, The content of fluoride etc. was adjusted.

Table 5 shows the amount of Nb added to the coating material and the amount of Nb in the weld metal.
The content, weld metal hardness, and presence or absence of weld cracking are summarized. As is clear from Table 5, when the Nb content in the weld metal is less than 0.3%, weld cracks sometimes occur even though the hardness of the weld metal is relatively low, which is undesirable. .

Also, if the content exceeds 2%, the hardness of the weld metal will increase by Hv3.
If it exceeds 8O, the deposited metal becomes brittle and weld cracking becomes noticeable. If the Nb content in the weld metal is within the range of 0.3 to 2%, weld cracking will not occur.
A sound weld was obtained. Example 3 In the above-mentioned example, a pure Ni wire was used as the welding rod core wire, and it was excellent in welding work on cast iron, and the resulting weld metal had good wear resistance and galling resistance, and was particularly suitable for press molds. It fully demonstrates its function as an overlay welding material.

However, pure Ni wire is expensive, so in order to satisfy the above-mentioned functions using a cheaper Fe-Ni wire,
Various studies were conducted by coating Fe--Ni wires having the chemical compositions shown in Table 7 with coating agents having the compounding ratios shown in Table 6. Therefore, welding rods were prepared in the same manner as in Example 1, thick welding was performed using each welding rod, and each performance was evaluated.

show.

The results are shown in Table 8 and Table 9 Table 8 shows the chemical composition of the weld metal by the above welding rod,
Table 9 shows the evaluation of each test result such as weld metal hardness, welding work conditions, wear resistance, and galling resistance.

Tables 8 and 9 also include commercially available Fe-Ni
Similar evaluation results were also shown for overlay welding materials for cast iron. As a result, Taki 13 to 7 f6.18 showed excellent wear resistance due to the weld metal containing C, Si, B, Nb, etc., but Taki 18 was inferior in terms of galling resistance. It's on. The reason for this is that B in the weld metal
, Nb, etc. form excessive carbides at grain boundaries,
It was confirmed that the edges were scratches on the panel surface. On the other hand, because the Ni content in the weld metal decreased, it is possible that the excellent slip characteristics were inhibited, so the influence of the Ni content on the galling resistance was investigated in more detail in Example 4. Example 4 Table 10 shows the blending ratio of the coating material for the welding rod used in this example.

This blending ratio is based on Taki 13 in Table 6, with the amounts of Si, B, Nb, and C constant, and the amount of Fe ranging from 24% to
Ni in the weld metal can be reduced by varying the range of 43%.
The effect of the content on galling resistance was clarified. At this time, other coating materials were A6. The ratio was the same as that of l3. The properties of the obtained weld metal are summarized in Table 11.
In this Example 4, it was confirmed using a microscope that there was no generation of carbides in any of the weld metals to the extent that they caused galling as shown in Example 3.

Furthermore, as is clear from the results in Table 11, if the Ni content in the weld metal is 40% or more, seizure or galling will occur due to its excellent sliding properties during sliding contact with the steel plate during press forming. It was found that the galling resistance was very good. In addition, each of the above-mentioned examples takes as an example a case in which the mold is used for overlay welding of a part of a press-forming mold that is subjected to extreme pressure during processing and is susceptible to wear, seizure, galling, etc. of the mold. However, it is obvious that the present invention is not limited to such uses, and of course, when the base material is cast iron,
It can also exhibit sufficiently excellent wear resistance and galling resistance against other materials.

As is clear from the detailed description above, when the coated arter welding rod for surface hardfacing of the present invention is used, it can withstand seizure and galling phenomena, especially in press working, without causing any lubrication even without lubrication. Overlay welding of deposited metal that maintains wear conditions is possible, and since it is arc welding, overlay work is not only very simple and efficient, but also allows for re-repair of worn parts and local change of mold. It also has the economical advantage of being easy to perform, and has excellent effects.

Claims (1)

[Claims] 1 S is added to the Ni or Fe-Ni core wire as an alloying agent.
i: 5-13%, B: 1-5%, Nb: 0.4-4%,
C: For surface hardening, characterized in that it contains 1 to 6% and is coated with a coating material containing ordinary arc stabilizers such as carbonates and fluorides, slag forming agents, gas generating agents, etc. Covered arc welding rod. 2 Welded weld metal composition is Ni: 40% by weight
% or more, Si: 3-8%, B: 0.1-0.5%, Nb
The coated arc welding rod for surface hardfacing according to claim 1, comprising: 0.3 to 2% C, 0.2 to 1.5% C, and the remainder Fe and unavoidable impurities.