Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper

Definitions

• the present invention relates to a high corrosion resistance ⁇ alloy suitable as a material for exhaust gas members. Since the alloy of the present invention exhibits excellent corrosion resistance to both alkaline and acidic substances, it has excellent high-temperature oxidation resistance at the same time. It is particularly suitable as a material constituting an automobile exhaust gas system that is subjected to erosive action by water and exposed to a high-temperature oxidizing atmosphere. ,
• Aluminum plating plates have the advantage that they are less expensive than heat-resistant stainless steel containing many alloying elements. Since it has a high degree of high temperature oxidation resistance, it is often used in automobile exhaust gas pipeline components.
• Japanese Patent Publication No. 54-23327 discloses that, in weight%, more than 5% and less than 11.5% ⁇ 1>, 0.5 to 2.0% S i, C up to 0.05, 0.1 to 0.4% Mn, and, in some cases, a small amount of Ti and Zr sufficient to combine with C and N in the element to form carbides and nitrides. It exhibits at least one kind of oxidation resistance, which is excellent in additivity and manufacturability, with the balance being Fe and unavoidable impurities.
• Japanese Patent Publication No. 54-35571 discloses that, in terms of% by weight, Cr of not less than 3.0% and not more than 6.0%, Si of 0.5 or 2.0%, and the content of unavoidable impurities of not more than 4.0%. ,, Mix up to 0.5%, C up to 0.05%, and in some cases, at least one kind of Ti and Zr up to 0.9%, the remainder being F e discloses oxidation resistance, which consists of unavoidable impurities.
• Japanese Patent Application Laid-Open No. 58-224148 discloses that, in weight percent, C up to 0.02%, Si of more than 1.5% and less than 3.0%, Cr, 0,05 of more than 5.0% and less than 10.0. Or 0.80% Cu, 0.003% or less S, 0.02% or less N, and in some cases, one or two of Ti, Nb, and Zr Chromium II for automobile exhaust system components containing 0.30% or less in total, with the balance being Fe and unavoidable impurities, will be disclosed.
• Japanese Patent Publication No. 59-179758 discloses that in weight%, C up to 0.02%, S i of 0.30% or 2.0%, M ⁇ of 1.0% or less, C ⁇ of less than 5.0% and less than 10.0%. r, 0.05 or 0.80% C u of 1.0 or 4.0 or about £, S of 0.003% or less, N of .02% or less, and depending on the case, a kind of Ti, Nb and Zr Alternatively, a chromium net for automobile exhaust system members will be disclosed, with a total of less than 0.50% of two or more types, with the remainder being Fe and unavoidable impurities.
• the exhaust gas pipe of the automobile is a front tube, exhaust gas purifying device (converter using a catalyst), and a center from the side near the engine. It is constructed by connecting parts such as a valve, a muffler, and a valve in order, but especially when the engine is started. Since the pipe line is not warmed up in + minutes, the moisture in the exhaust gas condenses in the pipe line, and the dew water accumulates in the muffler, for example. It adheres to the pipe wall.
• This condensed water evaporates as the temperature of the exhaust gas path rises, and during that time, the condensed water flows from the alkaline side to the acid side.
• the properties change. This is because the degree to which the various components in the exhaust gas dissolve in the condensed water varies depending on the temperature, and the components that have already been dissolved during the evaporation of the condensed water. It causes decomposition and scattering, and it is thought that the degree of the decomposition varies depending on the temperature and the components, and that this is the cause. Therefore, when the vehicle exhaust system members eventually become high, In addition to the high-temperature oxidation resistance of steel, corrosion resistance to aluminum alloys and corrosion resistance to acids are required.
• the aluminum plating plate (usually an I-type aluminum plating plate with an appropriate amount of Si in it) is the aluminum plating plate.
• the coating layer did not have sufficient corrosion resistance to alkaline dew water, and the base plate did not have sufficient corrosion resistance to acidic dew water.
• JP-B-54-23327 and JP-B-54-35571 mentioned above propose oxidation-resistant steel suitable for automobile exhaust system members, but both of these publications have the problem of wet corrosion. Has not been touched.
• its oxidation resistance can be achieved by adding expensive Cr in an amount of 5% or more without the addition of A ⁇ (Japanese Patent Publication No. 54-23327). ).
• the amount of Cr added to achieve the desired oxidation resistance depends on the addition of ⁇ ⁇ . Although it can be lowered to 6% or lower, A reduces the workability of steel (Japanese Patent Publication No. 54-35571). Both publications teach that workability can be improved by the addition of Ti and / or Zr. However, Ti and Zr are very expensive.
• JP-A-58-224148 and JP-B-59-179758 propose a corrosion-resistant chromium suitable for use in automobile exhaust system members, and both of these publications have the desired corrosion resistance and corrosion resistance. It is emphasized that Cr must be 5% or more to achieve high temperature oxidation resistance.
• the purpose is to provide a low alloy material for components.
• the present inventors do not properly crane Cr, Si, Cu and Ni even if the Cr content is 5.0% or less. For example, they found that the above-mentioned resistance to corrosion and oxidation, which are required for automobile exhaust system components, can be achieved with a minimum amount of alloying elements. We have also found that increasing the P content can further improve the corrosion resistance of this low alloy ⁇ .
• the high corrosion-resistant low alloy of the present invention which is particularly suitable as a material for an automobile exhaust system, has a weight of-C of up to 0.06% and no C and 0.30. 1.50% S i, M n up to 0.50%, 1.50 to 5,0% Cr, and at least one of Cu or Ni 0.10 to 0.50 % And the remainder consists of Fe and unavoidable impurities.
• the Shosho edible low alloy ⁇ of the present invention which is particularly suitable as an automobile exhaust system member, has a C, 0, 30 or 1.50% S i of up to 0.06% by weight. , Mn to 0.50%, 1.50 to 5.0% Cr, 0.030 to 0.100% P, and at least 0.10 of at least one of Cu or Ni However, it is contained in the range of 0.50%, with the balance being Fe and unavoidable impurities.
• C forms carbides with Cr and reduces the amount of Cr dissolved in the matrix, thereby reducing the effect of Cr on improving corrosion resistance.
• C it is preferable that C be small because the presence of the formed carbide itself promotes corrosion.
• the corrosion resistance is improved comprehensively by Cr, Si, Cu, Ni, P, etc.
• sufficient corrosion resistance is achieved even if C is allowed up to 0.06%. Since it can be maintained, the upper limit of C should be 0.06%, preferably less than 0.05%.
• Si improves the high-temperature oxidation resistance of ⁇ .
• the present inventors have shown that at low Cr ⁇ , Si acts synergistically with Cu and No or Ni to increase its corrosion resistance. I found it.
• at least 0.3% Si is required. This effect of Si is particularly prominent at low Cr contents, and becomes more pronounced as Si increases.
• it exceeds 1.50% the embrittlement of the material becomes remarkable, the cold workability becomes difficult, and the members constituting the exhaust gas path of the motor vehicle become difficult. In some cases, it may be difficult to process into the required complex shape. Therefore, it is necessary to avoid adding more than 1.50%.
• M ⁇ should have a small content from the viewpoint of corrosion resistance, but is an element necessary for the deoxidation reaction and sulfide formation in the manufacturing process.
• Mn up to 0.50% is acceptable.
• the Mn content should not exceed 0.3%.
• the amount of Cr required to achieve the desired corrosion resistance and high-temperature oxidation resistance is determined by appropriately determining the other alloying elements, in particular, Si, Cu, and Ni. 'Lance can be advantageously reduced to less than 5.0%. However, at least 1.50 is required to obtain satisfactory corrosion resistance and high temperature oxidation resistance. % Cr is required.
• Ni and Cu alone or in combination, have a very beneficial effect on the corrosion resistance, together with Si, even in amounts of Cr below 5.0%. .
• at least 0.10% Cu or at least 0.10% Ni is required.
• excessive addition of Cu causes slab cracking and surface flaws due to brittleness during ripening, and also lowers workability due to the precipitation hardening of Cu and, at the same time, lowers corrosion resistance. Will also have a negative effect. For this reason, the upper limit value of Cu is set to 0.50%.
• Ni not only suppresses hot brittleness due to Cu, but also has the effect of improving the corrosion resistance by increasing the solubility of Cu in water. Therefore, it is preferable to add Cu and Ni in combination.
• the upper limit of Ni is not particularly critical, but the effect of adding Ni exceeds about 0.50% and saturates, so from an economical point of view, the upper limit is also set. To 0.50%.
• P advantageously acts to enhance the corrosion resistance of the low alloy of the present invention.
• it is preferable to keep it at least at the .030% P level. This means that in the production process of the present invention, the dwarf does not have to be reduced to 0.030% or less. However, excess P levels, such as over .100%, should be avoided. Otherwise, in terms of weldability and workability, It will have a bad effect.
• the present invention can be manufactured according to a common manufacturing method.
• an impurity element unavoidably contained in the production for example, S, N, 0, A £, etc. is inevitable. Even if it is contained as an impurity in the range where it is specifically contained, it exhibits sufficient corrosion resistance. This means that it can be manufactured economically in that it does not require a special degassing process.
• the alloy of the present invention when used as a material constituting a vehicle exhaust gas honorable road exposed to a special corrosive environment as described above, is used as an example.
• a material constituting a vehicle exhaust gas honorable road exposed to a special corrosive environment as described above is used as an example.
• it shows at least twice the corrosion resistance (durable life) of conventional aluminum plating plates. Since the alloy steel of the present invention is not an alloy having a high content of expensive alloying elements, it is economically advantageous in that it can be manufactured at low cost.
• Test specimen A disc of SOBI BI diameter was cut out from a plate with a thickness of 1.0m, and the center of the disc was made hemispherical by an Ericssen tester. The test piece was subjected to overhanging processing (processing to form a hemispherical recess having a diameter of 25 mm and a maximum depth of the center of 4. Omm).
• the representative composition of the alkaline dew was retained because the dew gas condensed at the beginning of engine startup was an alkaline aqueous solution.
• the test solution A After immersing the test piece used for the corrosion resistance test in the test solution A having the following resistance at room temperature for 3 minutes at room temperature, the test solution A was subjected to the above-mentioned hemispherical recess ( Removed from the liquid in a state filled with the liquid, and then kept in a warm air atmosphere at 80 for 17 minutes, during which time the liquid in the liquid pool is completely removed. The process of evaporating to dryness is regarded as one cycle. The cycle is repeated 1080 times. -When the corrosion test of this 1080 cycles is completed, the amount of corrosion reduction (gr) and the amount of thickness reduction (mm) of each test piece are measured, and the bitting color is measured. Visually observe the presence or absence of a version.
• This liquid contains the following ion components that are actually contained in the condensed water that remains in the muffler of the exhaust gas of the vehicle.
• the pH was adjusted with ammonium salt so that the pH value was constant at 8.8.
• the addition of activated carbon is a reproduction of the fact that a large amount of unburned carbon has adhered to the muffler.
• test liquid B was removed from the liquid with the test piece B filled with liquid. After drying for 15 minutes at 120 and then for 10 minutes in a furnace maintained at 500, high temperature oxidation is performed, and then cooling to room temperature. Processing is one cycle. This cycle is returned 41 times. After the corrosion test of 41 cycles was completed, the amount of corrosion (gr) of each specimen was measured and the surface condition was observed.
• This solution is an acidic aqueous solution when the concentration of the vehicle exhaust gas condensed water equivalent to test solution A is concentrated to 140 by holding the solution at 60 ° C.
• the sulfuric acid pH was adjusted so that the pH value was constant at 4.0.
• the liquid set is as follows
• This test is a weighted test of Test I, and some of the samples that have completed Test I are subjected to the same cycle as Test II for 250 cycles ( After a total of 291 cycles, the corrosion loss (gr) is measured.
• the alloy of the present invention was subjected to high-temperature oxidation due to the wet corrosion due to the dew water of the exhaust gas from the automobile and the high-temperature oxidation after the wet corrosion. It shows that it can withstand a special and severe corrosive environment, which repeatedly cycles through the cycle of receiving food. This is described in detail below.
• Si plays an important role in the present invention.
• Si plays an important role in the present invention.
• Si As shown in the comparative networks IL12, 13, 14 and 16, when the amount of swelling is less than 0.3%, even if Cr, Ni, Cu, etc. are occupied, it is supposed to be occupied.
• sufficient corrosion resistance as in the present invention cannot be obtained.
• Si of 0.3% or more is required.
• the effect of this Si on improving the corrosion resistance to exhaust gas dew condensation water and the effect on the high-temperature oxidation resistance at around 500 at 500 degrees are very remarkable.
• the Cr content is low, the effect of this Cr becomes remarkable. This can be seen by comparing the present invention ⁇ 6 and ⁇ 7 with the comparative ⁇ 12.
• Ni and Cu are very important for enhancing the corrosion resistance of the present invention in the presence of Cr of 5% or less and Si of 0.30% or more to exhaust gas and condensed water. Use it for your benefit. This is clear from comparison of the comparative example ( ⁇ 11-14) with the present invention. 'This effect of Ni and Cu is exhibited by addition of 0.10% or more. The fact that this fact was found has one of the features of the present invention II. Note that Ni not only suppresses hot brittleness due to Cu, but also has the effect of improving the corrosion resistance by reducing the solubility of Ci in the water.
• the present invention ⁇ 1 to 10 show better results than the aluminum mirror ( ⁇ ⁇ 18).
• the present invention is based on an aluminum plating plate for a corrosive environment which is repeatedly subjected to an alkaline, acidic aqueous solution and high-temperature oxidation. Rimo shows much better resistance.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Exhaust Silencers (AREA)

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• 1986
  • 1986-01-11 DE DE19863690011 patent/DE3690011T1/de not_active Ceased
  • 1986-01-11 KR KR1019860700618A patent/KR910006031B1/ko not_active Expired
  • 1986-01-11 WO PCT/JP1986/000008 patent/WO1986004097A1/ja active Application Filing

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