TWI570249B - Austenitic alloy slab and method of producing thereof - Google Patents

Description

Vostian iron alloy steel embryo and manufacturing method thereof

The present invention relates to a Worthfield iron-based alloy steel preform and a method for producing the same, and more particularly to a method for producing a crack defect ratio of a Worstian iron-based alloy steel preform obtained by a thermal processing step.

Common Worth Iron alloy steel embryos include nickel-based alloy steel embryos (such as Alloy 800H, A-285, A-625 or A-718, etc.), Worthfield iron-based stainless steel embryos (such as 309 or 310 stainless steel), Nickel-copper alloy steel embryos (such as Alloy 400, 500K), etc., because the steel embryo contains a large amount of nickel, it is mainly a face-centered cubic Worcester iron structure. The above-mentioned Worthfield iron-based alloy steel is often used in products requiring high-temperature mechanical properties, such as engine components, turbine engine fasteners, high-temperature bearings, furnace covers, or pipelines of petrochemical plants.

In general, Worthite iron alloy steel embryos can be prepared by fuel furnace melting or non-vacuum electric furnace melting. In addition, a process such as Argon Oxygen Decarburization (AOD) or Vacuum Oxygen Decarburization (VOD) may be selectively performed to obtain a molded steel or continuous cast steel. The obtained cast steel or continuous casting steel embryo can be subsequently subjected to a temperature of 850 ° C to 1250 ° C. A forming step such as forging or rolling to apply a Worthfield iron-based alloy steel in various fields.

However, if the Worthfield iron-based alloy steel is molded into a die-cast steel blank by molding, the yield is low and the cost of the forging process is increased, so that the cost is increased. On the other hand, if the Worthite iron-based alloy steel is made into a continuous-cast steel preform by continuous casting, it is necessary to undergo a cutting step before the above-mentioned forming step to obtain a steel preform of a predetermined size. However, since the continuous casting steel embryo is in the process of solidification, it is easy to have a central shrinkage hole or a loose structure, so that a large number of cracks may occur in the cross section of the continuously cast steel preform after cutting. The above-mentioned crack defect ratio is as high as 0.83, which causes severe cracks in subsequent processing (for example, rolling or forging), thereby lowering the yield of the obtained product.

It is known that there is a method for improving the crack defect ratio of the Wolsfield iron-based alloy steel. The method is to control the temperature gradient inside and outside the continuous casting steel, and adjust the minimum down-pressure of the pass to roll the continuous casting steel. . The above method needs to reduce the surface temperature of the continuous casting steel embryo by using high-pressure water, and further increase the degree of deformation inside the continuous casting steel embryo, so as to facilitate the welding of the internal defects of the continuous casting steel embryo.

However, lowering the surface temperature of the continuous casting steel blank may cause the surface of the continuous casting steel to be embrittled, and it is easy to generate additional cracks during the rolling process. On the other hand, the steps of the above method are cumbersome.

Therefore, it is urgent to propose a Worthfield iron-based alloy steel embryo and a manufacturing method thereof for improving the proportion of crack defects of the Wolster iron-based alloy steel preform formed by the continuous casting steel embryo, thereby effectively improving the WoW ratio. The yield of the products made by the Stone Iron Alloy Steel.

Therefore, an aspect of the present invention provides a method for producing a Worthfield iron-based alloy steel preform, and the manufacturing method can effectively reduce the crack defect ratio of the obtained Worth Iron-based alloy steel.

Another aspect of the present invention provides a Worthfield iron-based alloy steel which is obtained by the above method.

According to the above aspect, a method of manufacturing a Worthfield iron-based alloy steel blank is proposed. In one embodiment, the above method first provides a Worthfield iron-based alloy material comprising 5 weight percent (wt.%) to 82 wt.% iron, 8 wt.% to 60 wt.% nickel, and 10 wt.% to 30 wt. .% chromium. Next, a continuous casting step is performed on the above-mentioned Worthfield iron-based alloy material to form a continuous casting steel blank. Then, the continuous casting steel blank is subjected to a thermal processing step to form a recrystallized steel preform, wherein the thermal processing reduction rate of the above thermal processing step may be 10% to 60%. Thereafter, the recrystallized steel embryo is subjected to a cutting step to obtain a Worthfield iron-based alloy steel.

According to an embodiment of the present invention, the Vostian iron-based alloy material may further comprise 0 to 0.2 wt.% of carbon, 0 to 6.0 wt.% of titanium, 0 to 16 wt.% of aluminum, and 0 to 12 wt.%. Molybdenum, 0 to 12 wt.% tungsten, 0 to 20 wt.% cobalt, 0 to 5 wt.% bismuth, 0 to 12 wt.% bismuth or any combination of the above.

According to an embodiment of the invention, the continuous casting step is carried out in a fuel furnace smelting or a non-vacuum furnace smelting.

According to an embodiment of the invention, the temperature of the thermal processing step may be from 850 ° C to 1250 ° C.

According to an embodiment of the invention, the thermal processing step comprises a rolling process, a forging process, an extrusion process or a stamping process.

According to an embodiment of the invention, the continuous casting steel preform has a uniform temperature.

According to an embodiment of the invention, the method further comprises performing a cooling step between the thermal processing step and the cutting step.

According to an embodiment of the invention, the cooling rate of the cooling step may be less than 100 ° C / hour.

According to the above aspect of the invention, a Worthfield iron-based alloy steel embryo is proposed. In one embodiment, the above-mentioned Vostian iron-based alloy steel germ system is produced by the above-described method for manufacturing a Worthfield iron-based alloy steel preform, wherein the Worthfield iron-based alloy steel embryo has a crack of not more than 0.37. The proportion of defects.

By applying the Vostian iron-based alloy steel embryo of the invention and the manufacturing method thereof, the proportion of crack defects of the Worthfield iron-based alloy steel formed by the continuous casting steel embryo can be effectively reduced, thereby improving the yield of the subsequent product.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a Worthfield iron-based alloy steel preform and a method of manufacturing the same to improve the conventional cracking of a Worthfield iron-based alloy steel formed from a continuously cast steel blank. The manufacturing method of the Worthfield iron-based alloy steel preform of the present invention is mainly to carry out a hot working step on the continuous casting steel blank to form a recrystallized steel embryo. In particular, adjust the hot work reduction rate of the thermal processing step to reduce the follow-up The proportion of crack defects in the formed Worth Iron-based alloy steel.

The continuous casting step referred to herein as the present invention can be carried out, for example, using a fuel furnace smelting or a non-vacuum electric furnace smelting.

The hot working step referred to herein as the hot working step may be, for example, a rolling process, a forging process, an extrusion process or a stamping process. In one embodiment, the temperature of the thermal processing step may be from 850 ° C to 1250 ° C, and the hot work reduction rate may be from 10% to 60%.

The hot work reduction rate referred to herein as the present invention is calculated as the sum of all cuts during the entire thermal processing step. In one example, the hot working step is a rolling process, so the hot working reduction rate refers to the sum of the cuts (or thickness differences) produced by all passes in the continuous casting of the steel without the hot working step. The ratio occupied by the thickness. The hot work reduction rate is calculated according to the following formula (I): hot work reduction rate = △ h / h ₀ × 100% (I)

Where Δh is the cut thickness, which is the thickness of the continuous casting steel (h ₀ ) minus the thickness of the recrystallized steel (h ₁ ).

The recrystallized steel germline referred to in the present invention induces recrystallization inside the continuous casting steel embryo due to the aforementioned thermal processing step, thereby eliminating (or rolling) the central shrinkage cavity and loose structure originally present in the continuous casting steel blank. The formed recrystallized steel embryo can effectively improve the quality of the Worthfield iron-based alloy steel.

Hereinafter, a method for producing the Worth Iron-based alloy steel preform of the present invention will be described in detail.

1. Provide Worthfield iron alloy materials

The manufacturing method of the present invention first provides a Worthfield iron-based alloy material which may comprise 5 weight percent (wt.%) to 82 wt.% iron, 8 wt.% to 60 wt.% nickel, and 10 wt.% to 30 wt.%. Chrome.

In an embodiment, the above-mentioned Vostian iron-based alloy material may further comprise 0 to 0.2 wt.% of carbon, 0 to 6.0 wt.% of titanium, 0 to 16.0 wt.% of aluminum, and 0 to 12.0 wt. % molybdenum, 0 to 12.0 wt.% tungsten, 0 to 20.0 wt.% cobalt, 0 to 5.0 wt.% bismuth, 0 to 12.0 wt.% bismuth or any combination of the above. In one example, the Worthite iron-based alloy material may contain 3.25 wt.% or less of copper, bismuth, and manganese.

Specifically, the Worthfield iron-based alloy material may include, but is not limited to, nickel-based alloys 800H, 825, A-286, 600, 625, C-276, 718; 400, K500, etc.; stainless steel series 201, 202, 205 series, 301 series, 314 series, 316 series, 317 series, 321 series, 329 series, 330 series, 347 series, 348 series, 384 series or any combination of the above.

2. Forming a continuous casting steel embryo

Next, a continuous casting step is performed on the above-mentioned Worthfield iron-based alloy material to form a continuous casting steel blank. The manner in which the continuous casting step is carried out has been described above, and will not be further described herein.

3. Thermal processing steps

The continuous casting steel blank is then subjected to a thermal processing step to form a recrystallized steel blank. The definitions of the thermal processing step and the recrystallized steel embryo are as described above. In particular, before the hot working step, the continuous casting steel embryo has The temperature of one, meaning that the surface temperature of the continuously cast steel embryo is the same or similar to the center temperature. If the hot working step is not performed or the hot working reduction rate of the continuous casting steel blank is less than 10%, the formed Worstian iron-based alloy steel embryo has a high proportion of crack defects. If the above-mentioned thermal processing reduction rate is greater than 60%, it is difficult to achieve the equipment and technology of the current industry, and the cost will be increased. In addition, unlike the general carbon steel alloy materials, the Worthfield iron-based alloy material still has a large deformation resistance at high temperatures (>850 °C) (the impedance is more than three times that of ordinary carbon steel), if the above-mentioned continuous casting steel When the surface temperature of the embryo is lowered, the resistance value of the steel embryo is greatly increased and the ductility is lowered, and it is difficult to perform hot working. Therefore, if the temperature difference between the surface temperature of the continuous casting steel and the center temperature is too large, for example, the temperature difference between the surface temperature and the center temperature is 100 ° C or more, the surface of the continuous casting steel blank is brittle and the crack is generated.

On the other hand, if the temperature of the above-described hot working step is lower than 850 ° C, the continuous casting steel embryo cannot be smoothly recrystallized, so that the problem that the proportion of crack defects of the Worthite iron-based alloy steel is too high cannot be improved. If the temperature of the above-mentioned hot working step is higher than 1250 ° C, the crystal of the continuous casting steel embryo grows too fast, and the crystal grains are too coarse and the mechanical strength is not good.

4. Cutting step

Thereafter, the recrystallized steel embryo is subjected to a cutting step to obtain a Worthfield iron-based alloy steel.

In an example, the cutting step can be performed, for example, using mechanical shearing, flame cutting, or laser cutting. Further, the cutting step of the present invention determines the size to be cut in accordance with the application of the obtained Wostian iron-based alloy steel blank, and the present invention is not limited to a specific size range.

5. Cooling step

In an embodiment, a cooling step can be performed between the hot working step and the cutting step. The cooling rate of the above cooling step is less than 100 ° C / hour. The cooling step can be carried out, for example, at room temperature, natural cooling, water cooling or air cooling, etc., and the invention is not limited thereto.

If the cooling rate is not less than 100 ° C / hour, the formed Worstian iron-based alloy steel germplasm is too dense, which is disadvantageous for the cutting step. Furthermore, the Wostian iron-based alloy steel embryo obtained by the invention is a crude steel embryo, which can be further refined afterwards. Therefore, if a Wostian iron-based alloy steel embryo with too dense texture is formed, it is easy to restrict its subsequent follow-up. The scope of application and increase the manufacturing cost of the application.

The Worstian iron-based alloy steel preform of the present invention can be obtained by the above method, and can have a crack defect ratio of not more than 0.37, so that the yield of the product obtained by applying the Worthfield iron-based alloy steel embryo is better. Hereinafter, specific embodiments of the method for producing the Wostian iron-based alloy steel preform of the present invention and evaluation methods thereof will be described using a plurality of examples.

Example 1

Example 1 first provided iron having a composition of 40.32 wt.%, 35 wt.% of nickel, 22 wt.% of chromium, 0.08 wt.% of carbon, a total of 1 wt.% of aluminum and titanium, and a total of 1.6 wt.%. The Worth Iron alloy material of copper, bismuth and manganese (ie, commercially available nickel-based alloy 800H). After the above-mentioned Worthfield iron-based alloy material is melted in a heating smelting furnace, a continuous casting step is performed to form Continuous casting steel blank, wherein the size of the continuous casting steel embryo is 200 mm × 1280 mm × 5000 mm. Next, the continuous casting steel blank is hot rolled at a temperature range of 850 ° C to 1250 ° C to form a recrystallized steel embryo, and the hot working reduction rate is 10%. The above recrystallized steel embryos were cooled to room temperature at a cooling rate of 34 ° C / hour. Thereafter, the recrystallized steel blank was cut into a Wolster iron-based alloy steel embryo of 200 mm × 250 mm × 5000 mm to detect the crack defect ratio.

Examples 2 to 5 and Comparative Example 1

Examples 2 to 5 and Comparative Example 1 were carried out in the same manner as in Example 1, except that Examples 2 to 5 and Comparative Example 1 were used to change the composition or process conditions of the Worthfield iron-based alloy material. The composition, process conditions, and evaluation results of the specific Wolster iron-based alloy materials of Examples 2 to 5 and Comparative Example 1 are shown in Table 1, and are not described herein.

Evaluation method Crack defect ratio

The proportion of crack defects referred to in the present invention is calculated by the following formula (II): crack defect ratio = l / L (II)

Where L is the length of the cut, and l is the sum of the cumulative lengths of crack defects present in the section of the length of the cut. The above-mentioned crack defect ratio is measured by surface liquid permeability test (Penetrant Testing; PT), and the test method is carried out according to the CNS 11376 forging liquid permeability test method.

According to the results of Table 1, it is known that the thermal processing step of the present invention The treated Worthfield iron-based alloy steel has a low proportion of crack defects, and the higher the value of the hot working reduction rate, the lower the proportion of crack defects achieved. For example, when the hot work reduction rate is 30%, the proportion of crack defects in the Worthite iron-based alloy steel can be reduced to 0.08, and when the hot work reduction rate is 45%, the Worthite iron-based alloy steel is The proportion of crack defects can be as low as about 0.01. If the hot working reduction rate is 60%, the proportion of crack defects less than 0.01 can be achieved.

On the other hand, according to Comparative Example 1 of Table 1, it was found that if the continuous casting steel blank was not subjected to the hot working step, a low crack defect ratio could not be obtained. Comparative Example 1 shows that if the above-mentioned hot working reduction rate is 0% (that is, the hot working step is not performed), the fracture defect ratio of the Worthfield iron-based alloy steel is as high as 0.83, which is liable to cause defects in subsequent applications.

By applying the Vostian iron-based alloy steel embryo of the present invention and the manufacturing method thereof, the crack caused by the cutting step directly after the continuous casting step can be effectively improved, so that the Worthfield iron-based alloy steel embryo can be obtained. The yield is improved.

While the invention has been described above in terms of several embodiments, it is not intended to limit the scope of the invention, and the invention may be practiced in various embodiments without departing from the spirit and scope of the invention. The scope of protection of the present invention is defined by the scope of the appended claims.

Claims (7)

A method for manufacturing a Wolster iron-based alloy steel preform, comprising: providing a Worthfield iron-based alloy material, wherein the Worthfield iron-based alloy material comprises: 5 wt% (wt.%) to 81.1 wt.% Iron; 8 wt.% to 60 wt.% nickel; 10 wt.% to 30 wt.% chromium; and 0.9 wt.% to 1.2 wt.% of one of titanium and aluminum, for the Worthfield iron-based alloy material a continuous casting step to form a continuous casting steel blank; performing a thermal processing step on the continuous casting steel blank to form a recrystallized steel embryo, wherein one of the thermal processing steps has a hot working reduction rate of 10% to 60%; a cooling step, wherein one of the cooling steps is a cooling rate of less than 100 ° C / hour; and a cutting step is performed on the recrystallized steel blank to obtain the Worthfield iron-based alloy steel. The method for producing a Wostian iron-based alloy steel preform according to the first aspect of the invention, wherein the Vostian iron-based alloy material further comprises 0 to 0.2 wt.% of carbon, 0 to 16 wt.% of aluminum, 0 to 12 wt.% of molybdenum, 0 to 12 wt.% of tungsten, 0 to 20 wt.% of cobalt, 0 to 5 wt.% of ruthenium, 0 to 12 wt.% of ruthenium or any combination thereof. For example, the Worth Iron System mentioned in the first paragraph of the patent application scope A method for producing an alloy steel preform, wherein the continuous casting step is performed by a fuel heating furnace smelting or a non-vacuum electric furnace melting. The method for producing a Wostian iron-based alloy steel preform according to the first aspect of the invention, wherein the temperature of one of the hot working steps is 850 ° C to 1250 ° C. The method for manufacturing a Worthfield iron-based alloy steel preform according to the first aspect of the invention, wherein the hot working step comprises a rolling process, a forging process, an extrusion process or a stamping process. The method for producing a Wostian iron-based alloy steel preform according to the first aspect of the invention, wherein the continuous casting steel preform has a uniform temperature. A Worthite iron-based alloy steel, which is produced by the method for producing a Worthite iron-based alloy steel according to any one of claims 1 to 6, wherein the Worth iron system The alloy steel embryo has a crack defect ratio of not more than 0.37.