Iron-based corrosion resistant wear resistant alloy and deposit welding material for obtaining the alloy

Abstract

To provide a high-performance, inexpensive low C-high Si-high Cr—B—Nb type iron-based corrosion-resistant and wear-resistant alloy that is extremely superior in corrosion resistance and wear resistance to 304 stainless steel, high-chromium cast iron and high carbon-high chromium cast-iron-type materials, has a high corrosion-resistant property that would never be obtained from a high carbon-high chromium carbide precipitation-type iron-based wear-resistant alloy and at the same time, a wear-resistant property that is superior to these metals, and further hardly causes brittle peeling that is inherent to high Si—containing steel. This alloy contains, all percentages by weight, C: 0.5 to 2.5% by weight, Si: 2.5 to 4.5%, Mn: 0 to 10% or less, Cr: 15% to 31%, Ni: 0 to 16%, Cu: 7% or less, Mo: 10% or less, B: 0.5% to 3.5%, and 0≦Nb+V≦8%, and in this structure, within a range of 15% Cr≦Cr<27%, (Si×B)≦2014 / Cr2+0.083Cr+1.05 is satisfied, within a range of 27%≦Cr≦31%, 1.25%≦(Si×B) 6.0% is satisfied, within a range of 15%≦Cr<20%, (Si×B) 570 / Cr2−0.066Cr+1.145 is satisfied, and within a range of 20%≦Cr≦31%, (Si×B)≧1.25 is satisfied.

Description

TECHNICAL FIELD[0001]The present invention relates to a low carbon-high silicon-boron-niobium-high chromium cast steel-type iron-based alloy that is superior in corrosion resistance and wear resistance, more specifically, to a high performance and inexpensive iron-based corrosion-resistant and wear-resistant alloy that is overwhelmingly superior in a corrosion-resistant property and wear-resistant property in comparison with those of 304 stainless steel, high-chromium cast iron, and high carbon-high chromium cast-iron-type material, has a high corrosion-resistant property that would never be obtained from a high carbon-high chromium carbide precipitation-type iron-based wear-resistant alloy and at the same time a wear-resistant property that is superior to that of these metals, and further hardly generate brittle peeling that is inherent to a high-Si content steel, and a clad (hard-surfacing) welding material used for obtaining the same.BACKGROUND ART[0002]In recent years, refuse in...

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Benefits of technology

[0128]The iron-based corrosion-resistant and wear-resistant metal is an epoch-making alloy which, although produced as an inexpensive iron-based alloy, endures sulfuric acid corrosion and hydrochloric acid corrosion as an alternative metal for expensive cobalt-based alloy and nickel-based alloy, also has a wear-resistant property that is the same as, or superior to that of these alloys, and is applicable as various welding materials, wear-resistant steel plates and cast steel.

[0129]From the world-wide viewpoint, at present, enormous amounts of expensive rarity-value alloys, such as cobalt and nickel, have been consumed as alloys for use as simply wear-resistant clad welding materials for production facilities, and worn and lost, dispersion-consumed, and discarded without being recovered in all over the world. In the future-oriented standpoint, the current wasteful consumptions of these rarity-value alloys will lead to lack of resources in the next generations sooner or later, and from now, effective utilizations of rare alloys and improvements of the resource-recovering efficiency have to be taken into consideration. Therefore, from the standpoint of effective utilizations of resources, the present inventors have proposed the utilization of silicon that has enormous amounts of deposits on the earth and is inexpensive since 26 years ago, and have continuously studied its application to clad welding materials as one of effective utilizations thereof.

[0130]At that time, an SLCE alloy having added amounts of alloy elements of C: 5.2%, Si: 12.3% and Cr: 20% (wear coefficient WR=7, average hardness HV=730) was developed, and a wear-resistant steel plate was produced. Many of this were supplied to copper refining factories, paper-manufacturing companies and cement companies, and were also exported to a paper-manufacturing company in Sweden. Although this alloy is strong against hydrochloric acid corrosion and sulfuric acid corrosion, and considerable evaluations were obtained; however, the alloy was poor in processability in a bending process or the like, and had a very brittle characteristic.

[0131]When Si was added to metal as an alloy, brittleness that was inherent to Si was caused, in particular, in an inexpensive iron-based alloy, making it very difficult to practically apply this as a welding material. In particular, this was characterized by the fact that innumerable cracks were caused in the thickness direction of the deposited metal. Because of its brittleness, slice-shaped peeling occur on the surface layer face of the clad welding metal and lump-shaped drops-off are generated from the base metal as the content thereof increases. Moreover, in the case of a wear-resistant steel plate, even upon applying a pressure by using a press or the like in a distortion removing process, peeling and drops-off occur, thereby limiting the application thereof to restricted usages. In the case where applied as a clad welding wire and a welding rod, even upon application of a slight impact to the cladded matter, peeling and drops-off occurred in the hardened clad welding metal.

[0132]After having studied for long years, the present inventors have given up the idea of applying Si alone, and succeeded in revising its brittleness by adding elements such as B, Nb and V so as to coexist therewith; thus, the present invention has been completed. In this method, although it is not possible to prevent Si from causing brittleness to an iron-based alloy, by using the characteristic that, when Si increases, Si forms chromium carbides in a high chromium-content steel into a needle-shape, niobium that forms niobium carbides that are miniaturized into spherical shapes or boron that allows plate-shaped borides having a net-work shape, an indefinite shape or a plate shape to be crystallized are added in order to suppress the amount of precipitation of needle-shaped carbides and also to compensate for the reduced portion; thus, the brittleness is suppressed and the wear-resistant property is improved. In particular, Nb is a very effective alloy element as an alloy that expands the adjusting range of the wear-resistant property so as to adjust the wear-resistant property.

Problems solved by technology

However, in a short period of time after the start of these operations, those members and devices are worn, burnt to be lost, and subjected to corrosive loss by the treated matters and heat, and there have been strong demands for prolonging the service life thereof.

However, these furnace devices and peripheral devices are exposed to such as high-temperature corrosive burning gases and acid dew-point corrosion that occurs upon stopping the furnace, and at present, it becomes difficult to deal with these conditions only by using simple high-temperature oxidation resistant property and wear-resistant property.

That is, unless a superior corrosion-resistant property is also provided, with a superior wear-resistant property possessed by the high carbon-high chromium cast iron-type clad welding material being maintained, it becomes difficult to prolong the service life of these various devices.

However, this alloy is very expensive in comparison with the iron-based alloy, failing to satisfy the cost-effectiveness balance.

Then, at present, since the high carbon-high chromium cast-iron-type clad welding material is inexpensive, this has been continuously used in most cases as the iron-based wear-resistant alloy; however, the corrosion-resistant property thereof is extremely inferior to that of cobalt- and nickel-based materials, and this is hardly called as a corrosion-resistant material.

However, since this has a carbon content that is extremely high, it can be said that the corrosion resistance is not sufficient.

Upon reviewing alloy elements contained in these cobalt-based alloys, it is found that large amounts of cobalt, tungsten and the like are contained so that these alloys are composed of very expensive elements.

Therefore, since the cobalt-based alloys are very expensive alloys, these do not become profitable when applied to a device having a very wide cladding area from the viewpoint of costs, and it is very difficult to satisfy the cost-effectiveness.

For this reason, the use of this alloy is considered to be limited only to applications in which a cladding process on a portion having an extremely limited small area can exert a great effect.

However, the greatest defect of the high Si-containing steel is to make the alloy extremely brittle, and because of this defect, a large amount of addition thereof to an iron-based wear-resistant cladding metal has been avoided even at present.

Incidentally, although a high Si-containing steel referred to as “Silicolloy” has already been produced, this metal was an alloy developed for use in wear-resistant purposes between metals, and its carbon content was in a level of 1 / 100 so that the amount of precipitation of carbides that give a wear-resistant property was extremely small, failing to be practically used in severely high-temperature grinding wear-resistant applications, as in the case of the application of the patented alloy (Patent Document 2).

The deposited metal of a high Si-containing steel has a characteristic of causing slice-shaped surface layer peeling on the surface layer, with the result that, upon carrying out a bending process thereon, there is a fear of scattering of slice-shaped portions.

Without satisfying this correlation formula, a sufficient precipitation of needle-shaped chromium carbides (Cr7C3) is not available, resulting in degradation of the high-temperature wear resistance.

However, the superior characteristic at high temperatures in contrast becomes a serious defect in its brittleness at normal temperature, and the extreme brittleness causes degradation of the bending processability, and when a wear-resistant steel plate cladded with the patented alloy is produced, the resulting product can be only applied to linear items, and with respect to items having a curvature, cladding processes need to be carried out by using a welding wire or a hand welding rod, always resulting in high production costs.

As described above, although the patented alloy can provide performances that are almost equivalent to the stellite alloy, its greatest defect is that the high Si-content easily causes slice-shaped peeling on the surface layer of the deposited metal, making it difficult, in particular, to produce a wear-resistant steel plate having a large area.

Moreover, upon carrying out a join-welding process between clad steels formed by using the same alloy, the hardened metal causes peeling when stretched by a welding stress, making it very difficult to carry out the join-welding process.

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