Martensitic stainless steel for compressor valve plate and preparation method of martensitic stainless steel

Abstract

The martensitic stainless steel comprises the following components in percentage by weight: 0.38 to 0.42 percent of C, 11.5 to 14.0 percent of Cr, 0.8 to 1.2 percent of Mo, 0.10 to 0.20 percent of V, less than or equal to 0.5 percent of Si, less than or equal to 0.5 percent of Mn, 0.001 to 0.015 percent of Ce, less than or equal to 0.005 percent of S, less than or equal to 0.008 percent of P and the balance of iron. The preparation method comprises the steps of burdening, smelting, hot rolling, annealing, cold rolling and heat treatment. Compared with the prior art, the martensitic stainless steel has high strength and high hardness.

Description

Technical Field

[0001] The invention relates to the field of stainless steel, and in particular to a martensitic stainless steel for a compressor valve sheet and a preparation method thereof. Background Art

[0002] The valve plate is the core component of the compressor of refrigeration equipment such as air conditioners. Its quality directly affects the working characteristics and service life of the compressor. When the compressor is working, the valve plate is subjected to high-frequency bending stress and impact stress for a long time, and works in a highly corrosive medium environment containing fluorine. The working environment is extremely harsh, which requires the valve plate material to have high strength, excellent wear resistance, corrosion resistance and good fatigue performance to meet the use requirements of the compressor. The currently commonly used martensitic stainless steel valve plate material has insufficient strength, hardness and toughness, coarse carbides in the structure, uneven distribution of carbides, etc., which affects the wear resistance and fatigue life of the material and cannot meet the use requirements of the compressor valve plate.

[0003] For example, the Chinese invention application with application number 202311384296.7 (application publication number CN117187511A) discloses a heating method for martensitic stainless steel for refrigeration compressor valve plates, including the following steps: placing the martensitic stainless steel continuous casting billet in a preheating furnace for heating and then taking it out of the furnace; the temperature system of the preheating furnace is: heat recovery section, first heating section, second heating section and third heating section, and the continuous casting billet is drawn out of the preheating furnace after the heating of the third heating section is completed; after the preheating furnace is heated, the martensitic stainless steel continuous casting billet is placed in a heating furnace for heating; after the martensitic stainless steel continuous casting billet is heated in the heating furnace, it is rolled into a hot-rolled black coil to obtain a finished product. This application has effectively improved the degree of segregation, and through a reasonable continuous casting billet heating method, it has achieved stable mass production of products; but it has failed to solve the problem of insufficient strength and hardness of martensitic stainless steel.

[0004] Therefore, it is necessary to improve the existing martensitic stainless steel used for compressor valve plates. Summary of the invention

[0005] The first technical problem to be solved by the present invention is to provide a high-strength and high-hardness martensitic stainless steel for compressor valve plates in view of the above technical status.

[0006] The second technical problem to be solved by the present invention is to provide a method for preparing martensitic stainless steel for compressor valve plates in view of the above technical status.

[0007] The technical solution adopted by the present invention to solve the above-mentioned first technical problem is: a martensitic stainless steel for compressor valve plates, characterized in that it includes the following components by weight percentage: C: 0.38-0.42%, Cr: 11.5-14.0%, Mo: 0.8-1.2%, V: 0.10-0.20%, Si≤0.5%, Mn≤0.5%, Ce: 0.001-0.015%, S≤0.005%, P≤0.008%, and the balance is iron.

[0008] Preferably, the Ce content is 0.002-0.010% by weight.

[0009] The technical solution adopted by the present invention to solve the above second technical problem is: a method for preparing martensitic stainless steel, characterized in that it comprises the following steps:

[0010] ① Ingredients: prepare stainless steel raw materials according to the above mass percentages;

[0011] ② Melting: Smelt the stainless steel raw materials except Ce in a vacuum induction furnace, add Ce, and then cast into ingots;

[0012] ③Hot rolling: the ingot is forged and hot rolled into slabs;

[0013] ④ Annealing;

[0014] ⑤Cold rolling: cold rolling into cold rolled sheet, the thickness of the cold rolled sheet is ≤1mm;

[0015] ⑥Heat treatment.

[0016] Preferably, the vacuum degree of smelting in step ② is 1Pa-5Pa, and the casting temperature is 1520°C-1550°C.

[0017] Preferably, the heating temperature of step ③ is 1190°C to 1210°C.

[0018] Preferably, the starting rolling temperature of step ③ is 1100°C to 1200°C, and the finishing rolling temperature is 800°C to 900°C.

[0019] Preferably, the annealing temperature of step ④ is 840° C. to 860° C., and the holding time is 1 to 2 hours; after annealing, the furnace is cooled to room temperature.

[0020] Preferably, the cold rolling in step ⑤ is a multi-pass cold rolling, and the deformation amount of each pass is 16-24%.

[0021] Preferably, the heat treatment in step ⑥ is: quenching at a temperature of 1040°C to 1060°C, quenching and heat preservation for 10 to 60 minutes, tempering after cooling, the tempering temperature is 190°C to 210°C, tempering and heat preservation for 1 to 2 hours, and then air cooling to room temperature.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] ① Adding Mo and V strong carbide alloying elements, the strong carbide alloying elements Mo and V interact with C and N in steel to form fine dispersed carbide particles, pinning dislocations, hindering dislocation movement in steel, and improving the strength of steel; adding Mo can form fine Mo 2 C phase, inhibiting the coarse M 23 C 6 Phase precipitation, reducing the average size of the precipitated phase, and improving the tempering stability of the steel; VC formed by adding V elements can inhibit the growth of austenite grains, refine the matrix structure, regulate the martensitic transformation, and improve the strength and toughness of the steel; at the same time, the addition of alloying elements can also improve the corrosion resistance of martensitic stainless steel;

[0024] ② The rare earth element Ce can deeply deoxidize and desulfurize, transforming the long strip-shaped MnS inclusions in the steel into spherical rare earth inclusions; at the same time, it purifies the grain boundaries, inhibits the segregation of low-melting point impurity elements at the grain boundaries, improves the grain boundary strength, controls the modification of inclusions, and improves the plasticity and toughness of the valve steel, thereby obtaining martensitic stainless steel for valves with matching strength and toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the metallographic structure of the martensitic stainless steel of Example 1;

[0026] Figure 2 Schematic diagram of carbide distribution of martensitic stainless steel in Example 1. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below with reference to the accompanying drawings.

[0028] Example 1

[0029] ① Ingredients: Calculated by weight percentage, the chemical composition of martensitic stainless steel for compressor valve plates is: C: 0.39%, Cr: 11.63%, Mo: 1.05%, V: 0.15%, Si: 0.075%, Mn: 0.054%, Ce: 0.0047%, S: 0.0044%, P: 0.0078%, and the balance is iron.

[0030] ② Melting: Smelt the stainless steel raw materials except Ce in a vacuum induction furnace, add Ce, and then cast into an ingot; the melting vacuum degree is 1.5Pa, and the pouring temperature is 1521°C.

[0031] ③ Hot rolling: the ingot is forged and hot rolled into a slab; the heating temperature is 1200℃; the starting rolling temperature is 1168℃, the final rolling temperature is 871℃, the reduction in each rolling pass is 15% to 25%, the total reduction is 83.8%, and the hot rolling is air-cooled to room temperature;

[0032] ④ Annealing: The hot-rolled slab is subjected to spheroidizing annealing at a temperature of 850°C for 2 hours and then cooled to room temperature;

[0033] ⑤ Cold rolling: cold rolling into cold rolled sheet, the thickness of the cold rolled sheet is ≤1mm; the reduction amount of each pass is 16-24%, and the total reduction amount is 75.6%;

[0034] ⑥ Heat treatment: The cold-rolled plate is heat treated at a quenching temperature of 1050°C for 10 minutes, oil cooled to room temperature and then tempered at a tempering temperature of 200°C for 1 hour, and then air cooled to room temperature.

[0035] Example 2

[0036] ① Ingredients: Calculated by weight percentage, the chemical composition of martensitic stainless steel for compressor valve plates is: C: 0.38%, Cr: 13.72%, Mo: 0.96%, V: 0.11%, Si: 0.055%, Mn: 0.074%, Ce: 0.0039%, S: 0.0031%, P: 0.0062%, and the balance is iron.

[0037] ② Melting: Smelt the stainless steel raw materials except Ce in a vacuum induction furnace, add Ce, and then cast into an ingot; the melting vacuum degree is 1.8 Pa, and the pouring temperature is 1532°C.

[0038] ③ Hot rolling: the ingot is forged and hot rolled into a slab; the heating temperature is 1200℃; the starting rolling temperature is 1157℃, the final rolling temperature is 892℃, the reduction per rolling pass is 15% to 25%, the total reduction is 76.4%, and the hot rolling is air-cooled to room temperature;

[0039] ④ Annealing: The hot-rolled slab is subjected to spheroidizing annealing at a temperature of 850°C for 2 hours and then cooled to room temperature;

[0040] ⑤ Cold rolling: cold rolling into cold rolled sheet, the thickness of the cold rolled sheet is ≤1mm; the reduction amount of each pass is 16-24%, and the total reduction amount is 79.8%;

[0041] ⑥ Heat treatment: The cold-rolled plate is heat treated at a quenching temperature of 1045°C for 20 minutes, oil cooled to room temperature and then tempered at a tempering temperature of 205°C for 1.5 hours, and then air cooled to room temperature.

[0042] Example 3

[0043] ① Ingredients: Calculated by weight percentage, the chemical composition of martensitic stainless steel for compressor valve plates is: C: 0.40%, Cr: 12.78%, Mo: 0.83%, V: 0.12%, Si: 0.062%, Mn: 0.090%, Ce: 0.0056%, S: 0.0037%, P: 0.0071%, and the balance is iron.

[0044] ② Melting: Smelt the stainless steel raw materials except Ce in a vacuum induction furnace, add Ce, and then cast into an ingot; the melting vacuum degree is 3.2 Pa, and the pouring temperature is 1547°C.

[0045] ③ Hot rolling: the ingot is forged and hot rolled into a slab; the heating temperature is 1200℃; the starting rolling temperature is 1178℃, the final rolling temperature is 885℃, the reduction per rolling pass is 15% to 25%, the total reduction is 80.6%, and the hot rolling is followed by air cooling to room temperature;

[0046] ④ Annealing: The hot-rolled slab is subjected to spheroidizing annealing at a temperature of 850°C for 2 hours and then cooled to room temperature;

[0047] ⑤ Cold rolling: cold rolling into cold rolled sheet, the thickness of the cold rolled sheet is ≤1mm; the reduction amount of each pass is 16-24%, and the total reduction amount is 87.6%;

[0048] ⑥ Heat treatment: The cold-rolled plate is heat treated at a quenching temperature of 1056°C for 40 minutes, oil cooled to room temperature and then tempered at a tempering temperature of 208°C for 1.8 hours, and then air cooled to room temperature.

[0049] Example 4

[0050] ① Ingredients: Calculated by weight percentage, the chemical composition of martensitic stainless steel for compressor valve plates is: C: 0.41%, Cr: 13.25%, Mo: 1.17%, V: 0.14%, Si: 0.035%, Mn: 0.088%, Ce: 0.0098%, S: 0.0026%, P: 0.0044%, and the balance is iron.

[0051] ② Melting: Smelt the stainless steel raw materials except Ce in a vacuum induction furnace, add Ce, and then cast into an ingot; the melting vacuum degree is 4.5Pa, and the pouring temperature is 1528°C.

[0052] ③ Hot rolling: the ingot is forged and hot rolled into a slab; the heating temperature is 1200℃; the starting rolling temperature is 1161℃, the final rolling temperature is 893℃, the reduction per rolling pass is 15% to 25%, the total reduction is 82.2%, and the hot rolling is followed by air cooling to room temperature;

[0053] ④ Annealing: The hot-rolled slab is subjected to spheroidizing annealing at a temperature of 850°C for 2 hours and then cooled to room temperature;

[0054] ⑤ Cold rolling: cold rolling into cold rolled sheet, the thickness of the cold rolled sheet is ≤1mm; the reduction amount of each pass is 16-24%, and the total reduction amount is 84.6%;

[0055] ⑥ Heat treatment: The cold-rolled plate is heat treated at a quenching temperature of 1059°C for 60 minutes, oil cooled to room temperature and then tempered at a tempering temperature of 196°C for 2 hours, and then air cooled to room temperature.

[0056] The mechanical properties of the examples were tested, and the results are shown in Table 1.

[0057] Table 1 Mechanical properties test results of Examples 1-4

[0058] Serial number <![CDATA[Yield strength / R P0.2 > Tensile strength / Rm Elongation / % Hardness / HRC Example 1 1453 1927 5.0 56.13 Example 2 1386 1853 5.5 53.39 Example 3 1368 1898 5.8 54.67 Example 4 1329 1827 5.3 54.21

[0059] As can be seen from Table 1, the martensitic stainless steel of the present invention has a tensile strength higher than 1800 MPa, a Rockwell hardness higher than 52 HRC, and an elongation higher than 5% after heat treatment. It has good toughness, plasticity, strength and hardness and can meet the use requirements of compressor valve plates.

[0060] Depend on Figure 1 , Figure 2 It can be seen that after rare earth modification and strengthening heat treatment, the martensitic stainless steel of Example 1 obtains a fine and uniform tempered martensitic structure, and the undissolved alloy carbides are dispersed in granular form, which hinders the growth of grains and pins dislocations, hindering the movement of dislocations and playing a role of dispersion strengthening. The results of the example show that the present invention forms fine and dispersed Mo in the valve plate steel by compositely adding Mo and V strong carbide alloy elements. 2 C and VC particles refine the grains and improve the strength and hardness of the valve plate steel; add an appropriate amount of rare earth element Ce to purify the grain boundaries, control the modification of inclusions, and improve the plasticity and toughness of the valve plate steel, thereby obtaining a martensitic stainless steel for valve plates with matching strength and toughness. The martensitic stainless steel of the present invention has a tensile strength of more than 1800MPa, a Rockwell hardness of more than 52HRC, and an elongation of more than 5% after heat treatment, which can meet the use requirements of compressor valve plates.

Claims

1. A martensitic stainless steel for compressor valve plate, characterized in that: Calculated by weight percentage, it includes the following components: C: 0.38-0.42%, Cr: 11.5-14.0%, Mo: 0.8-1.2%, V: 0.10-0.20%, Si≤0.5%, Mn≤0.5%, Ce: 0.001-0.015%, S≤0.005%, P≤0.008%, and the balance is iron.

2. The martensitic stainless steel for compressor valve sheet according to claim 1, characterized in that: Calculated by weight percentage, the content of Ce is 0.002-0.010%.

3. A method for preparing martensitic stainless steel as claimed in claim 1 or 2, characterized in that: The following steps are involved: ① Ingredients: prepare stainless steel raw materials according to the above mass percentages; ② Melting: Smelt the stainless steel raw materials except Ce in a vacuum induction furnace, add Ce, and then cast into ingots; ③Hot rolling: the ingot is heated and hot rolled into a slab; ④ Annealing; ⑤Cold rolling: cold rolling into cold rolled sheet, the thickness of the cold rolled sheet is ≤1mm; ⑥Heat treatment.

4. The method for preparing martensitic stainless steel according to claim 3, characterized in that: The vacuum degree of the smelting in step ② is 1Pa-5Pa, and the casting temperature is 1520°C-1550°C.

5. The method for preparing martensitic stainless steel according to claim 3, characterized in that: The heating temperature of step ③ is 1190°C to 1210°C.

6. The method for preparing martensitic stainless steel according to claim 5, characterized in that: The starting rolling temperature of step ③ is 1100°C to 1200°C, and the final rolling temperature is 800°C to 900°C.

7. The method for preparing martensitic stainless steel according to claim 3, characterized in that: The annealing temperature of step ④ is 840° C. to 860° C., and the holding time is 1 to 2 hours; after annealing, the furnace is cooled to room temperature.

8. The method for preparing martensitic stainless steel according to claim 3, characterized in that: The cold rolling in step ⑤ is a multi-pass cold rolling, and the deformation amount of each pass is 16-24%.

9. The method for preparing martensitic stainless steel according to claim 3, characterized in that: The heat treatment in step ⑥ is as follows: quenching at a temperature of 1040°C to 1060°C, quenching and heat preservation for 10 to 60 minutes, tempering after cooling, the tempering temperature is 190°C to 210°C, tempering and heat preservation for 1 to 2 hours, and then air cooling to room temperature.

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