TWI491744B - Austenitic alloy and method of making the same - Google Patents

Description

Vostian iron alloy and its manufacturing method

The present invention relates to an alloy and a method of manufacturing the same, and more particularly to a Worthfield iron-based alloy and a method of producing the same.

The Worthfield iron-based alloy can be used to make components requiring high-temperature mechanical properties, such as engine components, turbine engine fasteners, high-temperature bearings, and furnaces, because of its stable austenitic phase at high temperatures. Mechanical components such as the outer casing or petrochemical plant pipelines that are often in a high temperature state.

In general, after the hot working (such as hot rolling), the Worthite iron alloy needs to reduce the size of the Worthfield iron alloy through subsequent cold working (such as drawing) to reach the target size of the finished product. After the cold and hot processing, a solution heat treatment process is generally required to dissolve the carbides and γ' equivalent precipitates in the Worthite iron base to obtain a uniform supersaturated solid solution, thereby re-precipitating at low temperatures. Fine-grained, uniformly distributed carbides and reinforced phases such as γ'. The solution heat treatment process also has the function of annealing, which can eliminate the residual stress generated by the processing, and recrystallize the processed alloy to obtain a uniform metallographic structure and a suitable grain size, and ensure the material. Has good mechanical properties.

At present, the cold working method is to process the Wostian iron alloy to the finished product size using a process with a reduction rate of more than 16% per pass. The cold-worked Vostian iron-based alloy is then heated to a solution temperature to provide a uniform metallurgical structure and a suitable grain size to ensure good mechanical properties of the finished product. However, such a Worth Iron alloy is still unable to meet some of the needs of the use of better mechanical properties.

In view of this, it is urgent to propose a Worthfield iron-based alloy and a method for producing the same, thereby improving the mechanical properties of the conventional Worthfield iron-based alloy.

Therefore, an aspect of the present invention provides a method for manufacturing a Worthfield iron-based alloy, which is a cold working step of a small reduction rate of a Worthfield iron-based alloy casting embryo to form a Worthfield iron-based alloy. The workpiece is processed and the Worthite iron-based alloy processed product is annealed at a relatively low heating temperature to form a Worthfield iron-based alloy having better mechanical properties.

Next, another aspect of the present invention provides a Worthfield iron-based alloy in which the aforementioned Worth Iron-based alloy includes a plurality of crystal grains having a twin crystal structure and a cross section of a crystal having a twin crystal structure. The total area is greater than 70% of the cross-sectional area of the Worth Iron alloy.

According to the above aspect of the invention, a method of manufacturing a Worthfield iron-based alloy is proposed. In one embodiment, the Vostian iron-based alloy foundry is subjected to at least one cold working step to form a Worth Iron-based alloy processed product wherein the reduction rate for each cold working step is between 0.01% and 15%. Performing an annealing step to continuously heat the Worthite iron-based alloy workpiece for 5 to 150 minutes using a heating temperature of 700 ° C to less than 1100 ° C to form Vostian An iron-based alloy in which a Worstian iron-based alloy comprises a plurality of crystal grains having a twin crystal structure, and the sum of the cross-sectional areas of the crystal grains having the twin crystal structure is greater than 70% of the cross-sectional area of the Worthite iron-based alloy.

According to an embodiment of the invention, the reduction rate is 7% to 14%.

According to an embodiment of the invention, the heating temperature is 1050 ° C to 1080 ° C.

According to an embodiment of the invention, the sum of the cross-sectional areas of the crystal grains having the twin crystal structure is greater than 75% to 93% of the cross-sectional area of the Worth Iron alloy.

According to an embodiment of the invention, the tensile strength of the above-mentioned Worthite iron alloy casting embryo is less than 700 MPa.

According to an embodiment of the present invention, when the tensile strength of the above-mentioned Worstian iron-based alloy casting embryo is greater than 700 MPa, a selective annealing step is performed on the Worthite iron-based alloy casting embryo to make the Worthfield iron-based alloy casting embryo The tensile strength is less than 700 MPa, wherein the selective annealing step is to continuously heat the Wostian iron-based alloy castings at a heating temperature of from 700 ° C to less than 1100 ° C for 5 to 150 minutes.

According to an embodiment of the present invention, the above-mentioned Worth iron alloy casting has at least 5 to 70% by weight of nickel, 5 to 70% by weight of iron, 5 to 30% by weight of chromium, and the like. Avoid impurities.

According to an embodiment of the invention, the above-mentioned Vostian iron-based alloy casting embryo further comprises at least 0% by weight to 0.2% by weight of carbon, 0% by weight to 6% by weight of titanium, 0% by weight to 16% by weight of aluminum, 0% by weight to 12% by weight of phase, 0% by weight To 12% by weight of tungsten, 0% by weight to 20% by weight of cobalt, 0% by weight to 5% by weight of bismuth, 0% by weight to 12% by weight of bismuth, 0% by weight to 40% by weight of copper, 0% by weight To 2% by weight of bismuth and 0% by weight to 2% by weight of manganese.

According to an embodiment of the present invention, the method for manufacturing the Worthite iron-based alloy further comprises performing a thermal processing step to form a Worthfield iron-based alloy casting embryo, wherein the Wostian iron-based alloy casting embryo is at 850 ° C to 1250 ° C The heating environment is processed to form.

According to another aspect of the present invention, a Worthfield iron-based alloy is further produced by the above method.

The Vostian iron-based alloy of the present invention and the method for producing the same are subjected to a cold reduction step of a small reduction rate of the Worthite iron-based alloy casting embryo to form a Worthfield iron-based alloy processed product, and at a lower temperature heating temperature. The Worth Iron alloy processed material is annealed. Since the annealing treatment temperature of the present invention is lower than the solid solution temperature, the Worthfield iron-based alloy has a larger number of crystal grains having a twin crystal structure, thereby improving the tensile strength and the lodging strength of the Worthfield iron-based alloy. In addition, since the present invention performs annealing treatment using a lower temperature, and the heating time used is the same or similar to the heating time by a conventional technique at a higher temperature (for example, a solution temperature), The required heating time and the energy required for temperature rise during annealing are reduced, so that the cost and time required for manufacturing the Worth Iron-based alloy can be reduced.

100‧‧‧ method

110, 115, 120, 130, 140 ‧ ‧ steps

The above and other objects, features, advantages and embodiments of the present invention are made. The examples can be more clearly understood, and the description of the drawings is as follows: Fig. 1 is a flow chart showing a method of manufacturing a Worthfield iron-based alloy according to an embodiment of the present invention.

As described above, the present invention provides a cold working step of performing a small reduction rate on a Worthfield iron-based alloy casting embryo to form a Worthfield iron-based alloy processed product, and at a lower temperature heating temperature to the Worthite iron. The alloyed product is annealed to retain a large number of grains having a twin crystal structure in the Worthfield iron-based alloy, thereby enhancing the tensile strength and the lodging strength of the Worthfield iron-based alloy. Hereinafter, the Worthfield iron-based alloy of the present invention and a method for producing the same will be described.

Please refer to FIG. 1 , which is a schematic flow chart showing a method for manufacturing a Wolster iron-based alloy according to an embodiment of the present invention. In Fig. 1, first, as shown in step 110, the manufacturing method 100 of the Worthite iron-based alloy is provided with a Worthfield iron-based alloy casting. In an exemplary embodiment, the Worthfield iron alloy casting may be a nickel based alloy, a Worthfield iron based stainless steel or a nickel copper alloy. In some exemplary examples, the foregoing nickel-based alloy may be an alloy conforming to the standards of Alloy 800H, Alloy A-286, Alloy 625 or Alloy 718, and the aforementioned Worthfield iron-based stainless steel may be stainless steel conforming to standards of 309, 310, etc. The foregoing nickel-copper alloy may be an alloy conforming to the standards of Alloy 400, Alloy 500K, and the like.

In an exemplary embodiment, the aforementioned Worth Iron Alloy Castings can be made by smelting. In some instances, the smelting method may be simply smelting in a vacuum smelting (VIM or VAR) or electric furnace (EAF). Second, in another case In the above, the smelting method may be a method in which an electric furnace is smelted and then remelted by electroslag refining (EAF-ESR), followed by vacuum smelting and then electroslag remelting (VIM-ESR) or after vacuum melting. It is then remelted by vacuum electroslag (VIM-VAR).

In one example, the aforementioned Vostian iron-based alloy foundry may contain at least 5 weight percent to 70 weight percent nickel, 5 weight percent to 70 weight percent iron, 5 weight percent to 30 weight percent chromium, and others. Avoid impurities.

Secondly, in another example, the aforementioned Vostian iron-based alloy foundry may include, but is not limited to, 0% by weight to 0.2% by weight of carbon, 0% by weight to 6% by weight of titanium, and 0% by weight to 16% by weight. Aluminum, 0% by weight to 12% by weight of molybdenum, 0% by weight to 12% by weight of tungsten, 0% by weight to 20% by weight of cobalt, 0% by weight to 5% by weight of bismuth, 0% by weight to 12% by weight Thereafter, 0% by weight to 40% by weight of copper, 0% by weight to 2% by weight of bismuth, and 0% by weight to 2% by weight of manganese.

Next, as shown in step 120, at least one cold working step 120 is performed on the Vostian iron-based alloy slab to form a Worthian iron-based alloy processed product of a desired size or shape, wherein the reduction rate of each cold working step can be performed. For example, it is controlled at 0.01% to 15%. In an exemplary example, the aforementioned reduction rate is controlled between 7% and 14%. In an example, the cold working step 120 can include forging, extruding, stamping, drawing, rolling, or a combination thereof.

In an example, prior to performing the cold working step 120, The Worthfield iron-based alloy castings are subjected to a hot working step 115 such as forging or rolling forming, wherein the hot working step 115 for the Worthite iron-based alloy castings can be carried out in a heating environment of 850 ° C to 1250 ° C.

In an exemplary embodiment, when the tensile strength of the Worthite iron alloy casting is less than 700 MPa, the cold working step 120 can be directly performed. If the tensile strength of the Worthite iron alloy casting is greater than 700 MPa, the cold working step 120 cannot be smoothly performed because the strength of the Worthite iron alloy casting is too large. At this time, the selective annealing step 130 of the Worthite iron alloy casting embryo may be performed first, so that the tensile strength of the Worthite iron alloy casting embryo is less than 700 MPa. In one example, the selective annealing step 130 is to continuously heat the Vostian iron-based alloy castings at a heating temperature of from 700 ° C to less than 1100 ° C for 5 to 150 minutes. In other examples, one of the purposes of the cold working step 120 is to reduce the size of the Worthite iron alloy casting to the size of the Worth Iron alloy processing (ie, the size of the finished product), so if it is Voss The difference in size between the cast iron alloy and the finished product is too large, and it is also possible to produce a tensile strength greater than 700 MPa between the multiple cold working steps 120. At this time, the selective annealing step 130 may be performed first so that the tensile strength of the Worthite iron-based alloy slab is less than 700 MPa, whereby the subsequent cold working step 120 can be smoothly performed.

It is worth mentioning that the cold working step 120 can produce grains having a twin crystal structure in the Worthite iron alloy processing. These twin crystal grains enhance the mechanical properties of the Worthfield iron-based alloy, such as tensile strength and lodging strength. In addition, the heating temperature of the solution treatment of the general Worthite iron-based alloy is between 1100 ° C and 1250 ° C, but the cold-processed Worth iron system Therefore, the alloy processing product has a higher heating temperature for a solution treatment, and the number of crystal grains having a twin crystal structure in the alloy is reduced, thereby lowering the tensile strength and the lodging strength of the alloy as a whole. In contrast, the temperature used in the selective annealing step 130 of the present invention is less than 1100 ° C, so that more crystal grains having a twin crystal structure can be retained, thereby enhancing the mechanical properties of the Worthfield iron-based alloy.

Next, as shown in the annealing step 140, a continuous heat treatment can be used. The annealing furnace or the batch type heat treatment annealing furnace continuously heats the Worthite iron-based alloy workpiece at a heating temperature of 700 ° C to less than 1100 ° C for 5 to 150 minutes to form a Worthfield iron-based alloy. After the annealing step 140, the formed Wolster iron-based alloy comprises a plurality of crystal grains having a twin crystal structure, and the sum of the cross-sectional areas of the crystal grains having the twin crystal structure is larger than the cross-sectional area of the Worthite iron-based alloy. 70%. In an exemplary embodiment, the aforementioned heating temperature is from 1050 ° C to 1080 ° C. In another exemplary embodiment, the sum of the cross-sectional areas of the grains having the twin crystal structure is greater than 75% to 93% of the cross-sectional area of the Worth Iron alloy.

It is explained here that one of the features of the present invention is that the utilization is lower. The warm heating temperature (e.g., below the solid solution temperature of the Worthite iron-based alloy) is subjected to an annealing step 140 for the Worthite iron-based alloy workpiece, thereby retaining more of the twin-crystal structure formed in the cold working step 120. The grains are formed, and a Worthfield iron-based alloy having better mechanical properties can be formed. In addition, since the heating temperature used in the annealing step 140 of the present invention is low, and the heating time used is the same or similar to the heating time performed by a conventional technique at a higher temperature (for example, a solid solution temperature), The energy required for the annealing step 140 and the energy required for the temperature rise are reduced, so that the energy can be reduced. This expenditure and process time.

Another feature of the present invention resides in the low-cutting cold working step of the Worthite iron-based alloy slab and at a lower heating temperature (for example, lower than the solid solution temperature of the Worthite iron-based alloy). The Stone iron alloy workpiece is subjected to an annealing step 140. Therefore, in addition to retaining more crystal grains having a twin crystal structure formed in the cold working step 120, a Worthfield iron-based alloy having better mechanical properties can be formed. In addition, since the heating temperature used in the annealing step 140 of the present invention is low, and the heating time used is the same or similar to the heating time performed by a conventional technique at a higher temperature (for example, a solid solution temperature), Reduce energy costs and reduce process time. Moreover, since the reduction rate used in the cold working step 120 is low, when the Worstian iron alloy casting embryo is actually processed, the Worthfield iron alloy casting embryo can obtain a relatively uniform processing effect and can reduce the cause. Excessive reduction rate causes cracks or fractures on the surface of the Worthite iron alloy casting.

The following is a few examples to illustrate the Worth iron alloy of the present invention and the method for producing the same, which are not intended to limit the present invention, and therefore the scope of protection of the present invention is to be seen in the appended claims. The definition is subject to change.

Example 1 provides a Worthfield iron-based alloy casting composed of a nickel-based alloy, the composition of which comprises 32% by weight of nickel, 21% by weight of chromium, 44% by weight of iron, 0.08% by weight of carbon, and 1% by weight. Aluminum and titanium, as well as other minor additives, such as copper, tantalum or manganese alloy components. In the present embodiment, the Worthite iron alloy casting embryo is a wire having a wire diameter of 14 mm, but it is mentioned that other shapes (for example, bars) can also use.

Then, a Worth Iron-based alloy casting having a wire diameter of 14 mm was subjected to a number of cold working steps at a reduction rate of 14% per pass to form a Worstian iron-based alloy processed product having a wire diameter of 7.5 mm. Thereafter, the Worthite iron-based alloy processed product was continuously heated for 20 minutes by a heating temperature of 1080 ° C to form a Worthfield iron-based alloy. The formed Wolster iron-based alloy comprises a plurality of crystal grains having a twin crystal structure, and the sum of the cross-sectional areas of the crystal grains having the twin crystal structure is greater than 70% of the cross-sectional area of the Worthite iron-based alloy.

The fabrication methods of Examples 2 to 6 are the same as those of Embodiment 1, except that Examples 2 to 6 differ from Example 1 in the reduction ratios of Examples 2 to 6 and the heating temperature of the annealing step, and the reduction ratio and heating temperature are as follows: 1 is shown.

The manufacturing methods of Comparative Examples 1 to 6 are similar to those of Example 1, except that Comparative Examples 1 to 6 differ from the Examples in the reduction ratios of Comparative Examples 1 to 6 and the heating temperature of the annealing step, and the reduction ratio and heating temperature are also listed. In the above Table 1.

The properties of the Vostian iron-based alloys of Examples 1 to 6 and Comparative Examples 1 to 6 were measured, and the test items were as described later. First, the twin crystal density measurements of Examples 1 to 6 and Comparative Examples 1 to 6 were carried out, that is, the total of the cross-sectional areas of the crystal grains having the twin crystal structure was measured as a percentage of the cross-sectional area of the Worthite iron-based alloy. Briefly, any section of the Worth iron-based alloys of Examples 1 to 6 and Comparative Examples 1 to 6 was observed with an optical microscope, and a crystal grain having a twin crystal structure was observed based on the cross-sectional area of the cross-section of 100%. The percentage of the sum of the cross-sectional areas.

Table 1 above shows the results of the measured grain average particle diameters of the Worstian iron-based alloys of the respective examples and comparative examples. The percentage of the sum of the cross-sectional areas of the crystal grains having the twin crystal structure of Examples 1 to 6 was 75% to 93%. The percentage of the sum of the cross-sectional areas of the crystal grains having the twin crystal structure of Comparative Examples 1 to 6 was 30% to 45%.

Next, the tensile strength and the fall strength of Examples 1 to 6 and Comparative Examples 1 to 6 were measured. Briefly, the Worthite irons of Examples 1 to 6 and Comparative Examples 1 to 6 were subjected to a tensile tester (MTS-810, MTS, USA). The alloy is measured for tensile strength and strength.

From the results of the tensile strength and the fall strength of the Worthite iron-based alloys of the respective examples and comparative examples listed in Table 1 above, the tensile strength and the lodging strength of Examples 1 to 6 were 665 MPa to 720 MPa, respectively. 396MPa to 461MPa. The tensile strength and the lodging strength of Comparative Examples 1 to 6 were 565 MPa to 613 MPa and 278 MPa to 322 MPa, respectively. After aligning the examples and the comparative examples, it is understood that the Worstian iron-based alloy of the present invention does contain crystal grains having a twin crystal structure in a percentage of the total cross-sectional area, and also has preferable mechanical properties. Further, as can be seen from the above Table 1, if a small reduction ratio is used, preferable mechanical properties can be obtained.

In summary, it can be seen from the above embodiments of the present invention that the Worthfield iron-based alloy of the present invention and the method for producing the same are subjected to a cold working step of a Worthfield iron-based alloy casting embryo at a lower reduction rate, and at a lower temperature. The annealing step of the Worthite iron-based alloy processed article can make the obtained Worthfield iron-based alloy contain a higher percentage of crystal grains having a twin crystal structure, and can have better mechanical properties. In addition, since the heating temperature used in the annealing step is low, and the heating time used is the same or similar to the heating time by a conventional technique at a higher temperature (for example, a solution temperature), it can be lowered. The cost of energy during the annealing step is reduced and the process time can be reduced.

While the present invention has been described above by way of example, it is not intended to be construed as a limitation of the scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

100‧‧‧ method

110, 115, 120, 130, 140 ‧ ‧ steps

Claims (9)

A method for manufacturing a Worthite iron-based alloy, comprising: subjecting a Worthfield iron-based alloy casting to at least one cold working step to form a Worth Iron-based alloy processed product, wherein each of the at least one cold working step is performed A reduction rate is 0.01% to 15%, wherein the Vostian iron-based alloy casting embryo contains at least 5 to 70% by weight of nickel, 5 to 70% by weight of iron, and 5 to 30% by weight Chromium and other unavoidable impurities; and performing an annealing step to continuously heat the Vostian iron-based alloy workpiece for 5 to 150 minutes using a heating temperature of from 700 ° C to less than 1100 ° C to form the Vostian An iron-based alloy, wherein the Worthite iron-based alloy comprises a plurality of crystal grains having a twin crystal structure, and a total cross-sectional area of the crystal grains having the twin crystal structure is larger than a cross-sectional area of the Worthite iron-based alloy 70%. The method for producing a Vostian iron-based alloy according to claim 1, wherein the reduction ratio is 7% to 14%. The method for producing a Vostian iron-based alloy according to claim 1, wherein the heating temperature is from 1050 ° C to 1080 ° C. The method for producing a Worthite iron-based alloy according to claim 1, wherein the sum of the cross-sectional areas of the crystal grains having the twin crystal structure is greater than 75% to 93% of the cross-sectional area of the Worstian iron-based alloy. The method for producing a Vostian iron-based alloy according to claim 1, wherein the Worcester iron-based alloy casting has a tensile strength of less than 700 MPa. The method for producing a Worthite iron-based alloy according to claim 5, wherein when the tensile strength of the Worthite iron-based alloy casting is greater than 700 MPa, the selection of the Wostian iron-based alloy casting embryo is performed. An annealing step of causing the tensile strength of the Vostian iron-based alloy casting embryo to be less than 700 MPa, wherein the selective annealing step is to heat the Wolfstone iron-based alloy at a heating temperature of from 700 ° C to less than 1100 ° C. Continue heating for 5 to 150 minutes. The method for producing a Vostian iron-based alloy according to claim 2, wherein the Vostian iron-based alloy casting embryo further comprises at least: 0% by weight to 0.2% by weight of carbon; and 0% by weight to 6% by weight of titanium 0% by weight to 16% by weight of aluminum; 0% by weight to 12% by weight of molybdenum; 0% by weight to 12% by weight of tungsten; 0% by weight to 20% by weight of cobalt; 0% by weight to 5% by weight of bismuth 0% by weight to 12% by weight of bismuth; 0% by weight to 40% by weight of copper; 0% by weight to 2% by weight of bismuth; and 0% by weight to 2% by weight of manganese. The method for manufacturing a Vostian iron-based alloy according to claim 1, further comprising performing a thermal processing step to form the Vostian iron-based alloy casting embryo, wherein the Vostian iron-based alloy casting embryo is at 850 ° C It is formed by processing in a heating environment up to 1250 °C. A Worthfield iron-based alloy obtained by the method of any one of claims 1 to 8.