A method for inhibiting centerline segregation of alloying elements in super austenitic stainless steel die cast ingot

Abstract

The application provides a method for inhibiting center segregation of alloying elements of super-austenitic stainless steel die casting ingot, and relates to the technical field of super-austenitic stainless steel production. The application changes the traditional solidification mode from surface to inside by inserting a stainless steel rod, avoids the oxidation of the top layer of molten steel by sealing, and strengthens the heat and mass transfer between the steel rod and the superheated molten steel by rotating the steel rod, so as to reduce the enrichment of alloying elements in the center of the die casting ingot, solve the problem of serious center segregation of alloying elements of the super-austenitic stainless steel die casting ingot, improve the internal quality, and improve the yield of the super-austenitic stainless steel.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of super austenitic stainless steel production, and particularly relates to a method for inhibiting alloy element central segregation of super austenitic stainless steel mold ingot. BACKGROUND

[0002] In recent years, with the transformation and upgrading of key industries of national economy, the cultivation and development of strategic emerging industries and the construction of national key projects, the demand for corrosion-resistant materials such as austenitic stainless steel and nickel-based alloy is increasingly strong in the environment of marine engineering, petroleum chemical industry, etc. The super austenitic stainless steel improves the content of Cr, Ni, Mo and other alloys on the basis of ordinary austenitic stainless steel, and its corrosion resistance in the environment of flue gas desulfurization, seawater desalination, etc. is much stronger than that of ordinary austenitic stainless steel, not weaker than that of nickel-based alloy, and the cost advantage is very outstanding. It is a key material urgently needed by China's equipment manufacturing industry. However, the alloy content of super austenitic stainless steel is very rich, and the alloy elements are continuously enriched in the molten steel during solidification, causing serious central segregation of alloy elements in super austenitic stainless steel mold ingot. The serious central segregation causes difficult-to-solve inclusion and cracking problems, greatly reducing the yield of super austenitic stainless steel mold ingot.

[0003] Chinese patent with publication number CN10682538A discloses a casting method for improving the grain size and structure segregation of mold ingot, but the improvement effect of the method on structure segregation needs to be further improved. SUMMARY

[0004] The present application aims to provide a method for inhibiting the central segregation of alloy elements in super austenitic stainless steel mold ingot, which can significantly improve the problem of central segregation of alloy elements in super austenitic stainless steel mold ingot and improve the yield of super austenitic stainless steel.

[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0006] The present application provides a method for inhibiting the central segregation of alloy elements in super austenitic stainless steel mold ingot, comprising the following steps:

[0007] The superheated molten steel of super austenitic stainless steel is poured into a mold, a stainless steel rod is quickly inserted into the superheated molten steel, the rotational angular velocity of the stainless steel rod is a sinusoidal function, and the stainless steel rod is extracted after the stainless steel rod is melted in the superheated molten steel of stainless steel. The mold is extracted after the molten steel is completely solidified; and a cover is provided above the mold.

[0008] Preferably, the peak value n of the rotational speed of the stainless steel rod is 0.8-1.2 r / s, and the period is 0.5-1.5 s.

[0009] Preferably, the composition of the superheated steel liquid is: C≤0.04%, Mn≤5.00%, Cr: 19.0-26.0%, Ni: 17.0-26.0%, Mo: 2.0-8.0%, N: 0.15-0.58%, Cu: 0.20-1.20%, and the balance is Fe.

[0010] Preferably, the types of alloying elements in the stainless steel rod are the same as those in the superheated steel liquid, and the mass content of each alloying element in the stainless steel rod is 80-100% of the content of the same alloying element in the superheated steel liquid.

[0011] Preferably, the upper end of the stainless steel rod is in the shape of a cylinder, and the lower end is in the shape of an inverted cone, the height of the cylinder is L+a1, and the radius is 60-120 mm, and the taper of the inverted cone is 1:a2; wherein L is the depth of the stainless steel rod embedded in the steel rod clamp, and is 100-200 mm; a1 is 100-200 mm; a2 is a constant, and is 2-5.

[0012] Preferably, the insertion ratio of the stainless steel rod is α=KΔT 0.23 , wherein α is the insertion ratio of the stainless steel rod, ΔT is the superheat, ℃, and K is a coefficient, and is 0.005-0.010; the insertion depth of the stainless steel rod is calculated according to formula 1: Formula 1; in formula 1, ρ1 is the density of the stainless steel rod, kg / m 3 ; h is the depth of the stainless steel rod immersed in the superheated steel liquid, m; and M is the mass of the poured steel liquid, kg.

[0013] Preferably, the pouring height of the superheated steel liquid does not exceed 3 / 4 of the height of the mold.

[0014] Preferably, the superheat of the superheated steel liquid is 30-60 ℃.

[0015] The application provides a method for inhibiting the central segregation of alloying elements of a super-austenitic stainless steel die-cast ingot, which comprises the following steps: pouring a super-austenitic stainless steel superheated liquid into a mold, rapidly inserting a stainless steel rod into the superheated liquid, the angular velocity of rotation of the stainless steel rod is in a sinusoidal function rule, and the stainless steel rod is extracted after the stainless steel rod is melted in the superheated liquid, and the mold is demolded after the steel liquid is completely solidified; a cover is arranged above the mold.

[0016] The application changes the solidification mode of the die-cast ingot from the surface to the inside by rapidly feeding the stainless steel rod into the superheated steel liquid, strengthens the mass and heat transfer by the rotation of the steel rod, reduces the central enrichment of alloying elements, prevents the excessive oxidation of alloying elements by the cover, and further improves the central segregation of alloying elements of the super-austenitic stainless steel die-cast ingot. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 Structure diagram of the casting device used in the present application, wherein 1-casting mold; 2-stand; 3-crossbeam; 4-guide tube; 5-cover; 6-nut;

[0018] Figure 2 Structure diagram of the feeding rod device used in the present application, wherein 7-steel rod; 8-steel rod clamp; 9-longitudinal arm; 10-cross arm; 11-lifter; 12-support; 13-operating console; 14-roller;

[0019] Figure 3 Diagram of the change rule of the rotation angular velocity of the steel rod with time. DETAILED DESCRIPTION

[0020] The present application provides a method for inhibiting the central segregation of alloying elements of super-austenitic stainless steel die-cast ingot, comprising the following steps:

[0021] The super-austenitic stainless steel superheated liquid steel is poured into a casting mold, and a stainless steel rod is rapidly inserted into the superheated liquid steel, the rotation angular velocity of the stainless steel rod is a sinusoidal function rule, and the steel rod is extracted after the steel rod is melted in the superheated liquid steel, and the mold is demolded after the liquid steel is completely solidified.

[0022] As shown in Figure 1 and Figure 2 , the present application preferably uses a special casting mold with a stand and a special guide tube with a crossbeam and a protective cover, the cover 5 is covered above the casting mold, the crossbeam 3 is fixed on the stand 2 through the nut 6, and the inner cavity radius of the guide tube 4 is 1.2-1.4 times the radius of the cylindrical segment of the steel rod. The present application preferably fixes the stainless steel rod 7 on the steel rod clamp 8, raises the steel rod 7 to the upper side of the guide tube 4, and waits for use.

[0023] The present application pours the super-austenitic stainless steel superheated liquid steel into a casting mold. The present application preferably pours the super-austenitic stainless steel superheated liquid steel into the casting mold through the guide tube. In the present application, the pouring height of the superheated liquid steel is preferably not more than 3 / 4 of the height of the casting mold; the superheat degree of the superheated liquid steel is preferably 30-60℃, and more preferably 40-50℃.

[0024] In the present application, the composition of the superheated liquid steel is preferably, in terms of mass percentage: C≤0.04%, Mn≤5.00%, Cr: 19.0-26.0%, Ni: 17.0-26.0%, Mo: 2.0-8.0%, N: 0.15-0.58%, Cu: 0.20-1.20%, and the balance is Fe and other unavoidable impurity elements.

[0025] After pouring the superheated steel liquid, the stainless steel rod is rapidly inserted into the superheated steel liquid, the angular velocity of the stainless steel rod is a sinusoidal function, until the stainless steel rod is extracted after melting in the superheated steel liquid, and the mold is demolded after the steel liquid is completely solidified.

[0026] In the application, the shape of the upper end of the stainless steel rod is preferably cylindrical, and the shape of the lower end is preferably inverted conical, the height of the cylindrical shape is preferably L+a1, and the radius is preferably 60-120mm, and the taper of the inverted conical shape is preferably 1:a2; wherein L is the depth of the stainless steel rod embedded in the steel rod clamp, and the value is 100-200mm; a1 is 100-200mm; a2 is a constant, and the value is 2-5.

[0027] In the application, the types of alloying elements in the stainless steel rod are the same as those in the superheated steel liquid, and the mass content of each alloying element in the stainless steel rod is 80-100% of the content of the same alloying element in the superheated steel liquid.

[0028] In the application, the insertion ratio of the stainless steel rod is α=KΔT 0.23 , wherein α is the insertion ratio of the stainless steel rod, ΔT is the superheat, ℃, and K is a coefficient, and the value is 0.005-0.010; the insertion depth of the stainless steel rod is calculated according to formula 1: Formula 1; in formula 1, ρ1 is the density of the stainless steel rod, kg / m 3 ; h is the depth of the stainless steel rod immersed in the superheated steel liquid, m; and M is the mass of the poured steel liquid, kg.

[0029] In the application, the insertion ratio of the stainless steel rod is defined as the mass of the inserted stainless steel rod divided by the mass of the steel liquid in the mold.

[0030] The insertion ratio is controlled in the above range, which can prevent the insertion ratio from being too small to cause small insertion depth of the steel rod, and prevent the insertion ratio from being too large to cause incomplete melting of the steel rod, both of which are not conducive to improving the center segregation.

[0031] The application changes the solidification mode from the surface to the center in the traditional casting by inserting the stainless steel rod, avoids the oxidation of the top layer of the steel liquid by capping, and strengthens the heat and mass transfer between the steel rod and the superheated steel liquid by rotating the stainless steel rod, thereby reducing the enrichment of alloying elements in the center of the mold ingot, solving the problem of serious center segregation of alloying elements in the superalloy stainless steel mold ingot, improving the internal quality, and improving the yield of the superalloy stainless steel.

[0032] The method for suppressing the center segregation of alloying elements in the superalloy stainless steel mold ingot provided by the application will be described in detail in conjunction with the embodiments below, but they should not be understood as limiting the scope of protection of the application.

[0033] Comparative example 1

[0034] A super-austenitic stainless steel ingot was prepared in a mold with an inner cavity size of 280 mm in bottom diameter, 350 mm in top diameter, and 1000 mm in height. The super-austenitic stainless steel liquid was poured into the mold through a guide pipe, the poured liquid mass was 350 kg, the liquid superheat was 40℃, and the liquid composition (wt%) was C: 0.04, Mn: 3, Cr: 24, Ni: 22, Mo: 7, N: 0.5, Cu: 1.1, and the balance being Fe. After the liquid was completely solidified, the mold was removed, and the Mo element segregation was measured to be 1.97 at the center of the ingot.

[0035] Example 1

[0036] A stainless steel rod was prepared, the cylindrical section of the rod had a radius of 100 mm, and the inverted conical section had a taper of 1: a2, where a2 = 3. The stainless steel rod was fixed on a rod clamp and was ready for use, the composition (wt%) of the stainless steel rod was C: 0.04, Mn: 2.5, Cr: 22, Ni: 20, Mo: 7, N: 0.5, Cu: 1.0, and the balance being Fe and other unavoidable impurity elements; the density of the stainless steel rod was 7000 kg / m 3 .

[0037] A super-austenitic stainless steel ingot was prepared in a mold with an inner cavity size of 280 mm in bottom diameter, 350 mm in top diameter, and 1000 mm in height. The super-austenitic stainless steel liquid was poured into the mold, the poured liquid mass was 350 kg, the liquid superheat was 40℃, and the liquid composition (wt%) was C: 0.04, Mn: 3, Cr: 24, Ni: 22, Mo: 7, N: 0.5, Cu: 1.1, and the balance being Fe.

[0038] The stainless steel rod was quickly inserted into the superheated liquid, the angular velocity of the stainless steel rod was a sinusoidal function, and the stainless steel rod was slowly stirred in the superheated liquid until the rod was broken in the superheated liquid, then the rod was pulled out, the peak speed of the stainless steel rod was 1 r / s, the period was 2.8 s, and the insertion ratio of the stainless steel rod was a = KΔT 0.23 , where a is the insertion ratio of the rod, ΔT is the superheat, ℃, and K is a coefficient with a value of 0.007. The immersion depth of the rod in the superheated liquid was 0.3 m, which was calculated by the following formula:

[0039]

[0040] where p1 is the density of the rod, kg / m 3 ; h is the depth of the rod immersed in the liquid, m; and M is the mass of the poured liquid, kg.

[0041] After the steel liquid is completely solidified, the mold is demolded, and the Mo element segregation is 1.25 at the center of the mold ingot, which is reduced by 37% compared with the center segregation of Comparative Example 1.

[0042] Example 2

[0043] A stainless steel rod is made, the radius of the cylindrical section of the steel rod is 80 mm, the taper of the reverse taper section is 1: a2, wherein a2 = 4. The stainless steel rod is fixed on the steel rod clamp and waits for use, and the composition (wt%) of the steel rod is: C: 0.04, Mn: 2.0, Cr: 21, Ni: 21, Mo: 7, N: 0.4, Cu: 1.1, and the balance is Fe and other inevitable impurity elements; the density of the stainless steel rod is 7000 kg / m 3 .

[0044] A super austenitic stainless steel mold ingot is prepared in a mold with an inner cavity size of: bottom diameter 280 mm, top diameter 350 mm, height 1000 mm. The super austenitic stainless steel liquid is poured into the mold, the poured liquid mass is 350 kg, the liquid superheat is 40℃, and the composition (wt%) of the liquid is: C: 0.04, Mn: 3, Cr: 24, Ni: 22, Mo: 7, N: 0.5, Cu: 1.1, and the balance is Fe and other inevitable impurity elements.

[0045] The super austenitic stainless steel liquid is poured into the mold, the poured liquid mass is 350 kg, the liquid superheat is 40℃, and the composition (wt%) of the liquid is: C: 0.04, Mn: 3, Cr: 24, Ni: 22, Mo: 7, N: 0.5, Cu: 1.1, and the balance is Fe and other inevitable impurity elements.

[0046] The stainless steel rod is quickly inserted into the superheated liquid, the angular velocity of the rotating steel rod slowly stirs in the superheated liquid in a sinusoidal function, until the steel rod is melted in the superheated liquid and the steel rod is pulled out, the peak speed of the stainless steel rod is 1.2 r / s, the period is 2.3 s, and the insertion ratio of the steel rod is a = KΔT 0.23 , wherein a is the insertion ratio of the steel rod; ΔT is the superheat, ℃; K is the coefficient, and the value is 0.0086. The immersion depth of the steel rod in the superheated liquid is 0.4 m, which is calculated by the following formula:

[0047]

[0048] , wherein ρ1 is the density of the steel rod, kg / m 3 ; h is the depth of the steel rod immersed in the liquid, m; M is the mass of the poured liquid, kg.

[0049] After the steel liquid is completely solidified, the mold is demolded, and the Mo element segregation is 1.25 at the center of the mold ingot, which is reduced by 37% compared with the center segregation of Comparative Example 1.

[0050] From the results of the comparative examples and the examples, it can be seen that the present application can obviously reduce the center segregation of alloy elements of the mold casting ingot after the super-austenitic stainless steel liquid is inserted into the stainless steel rod, which shows that the present application has obvious improvement effect on the center quality of the super-austenitic stainless steel mold casting ingot.

[0051] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method of suppressing centerline segregation of alloying elements in a superaustenitic stainless steel die ingot, characterized by, It comprises the following steps: Pouring super-austenitic stainless steel liquid into a mold, inserting a stainless steel rod into the superheated liquid, the stainless steel rod rotates at a sine function law until the stainless steel rod is melted in the superheated liquid, then the stainless steel rod is pulled out, and the mold is demolded after the liquid is completely solidified; The mold is covered with a cover; The shape of the upper end of the stainless steel rod is cylindrical, and the shape of the lower end is inverted conical, the height of the cylindrical shape is L+a1, and the radius is 60-120 mm, the taper of the inverted conical shape is 1:a2; Wherein L is the depth of the stainless steel rod embedded in the steel rod clamp, the value is 100-200 mm; a1 is 100-200 mm; a2 is a constant, the value is 2-5; The insertion ratio of the stainless steel rod wherein, α is the insertion ratio of the stainless steel rod; is the superheat, ℃; K is a coefficient, and has a value of 0.005-0.010; the insertion depth of the stainless steel rod is calculated according to formula 1: Formula 1; in formula 1, ρ 1 is the density of the stainless steel rod, kg / m 3 ; h is the depth of the stainless steel rod immersed in the superheated steel liquid, m; M is the mass of the poured steel liquid, kg.

2. The method of claim 1, wherein, Peak rotation speed of the stainless steel bar n The range is 0.8~1.2 r / s, and the period is... s.

3. The method of claim 1, wherein, The composition of the superheated liquid is: C≤0.04%, Mn≤5.00%, Cr: 19.0-26.0%, Ni: 17.0-26.0%, Mo: 2.0-8.0%, N: 0.15-0.58%, Cu: 0.20-1.20%, the balance is Fe and other inevitable impurity elements.

4. The method according to claim 1 or 3, characterized in that, The types of alloying elements in the stainless steel rod are the same as those in the superheated liquid, and the mass content of each alloying element in the stainless steel rod is 80-100% of the content of the same alloying element in the superheated liquid.

5. The method of claim 1, wherein, The pouring height of the superheated liquid is not more than 3 / 4 of the height of the mold.

6. The method of claim 1, wherein, The superheating degree of the superheated liquid is 30-60℃.

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