Quenching and tempering method of 1.4104 stainless steel flat steel

Abstract

The invention discloses a quenching and tempering method for 1.4104 stainless steel flat steel, and aims to achieve the effects that the mechanical property meets the standard requirement, the cost is low, the production efficiency is high and the upgrading and reconstruction of equipment are accelerated by adopting the production method. Components and a quenching and tempering heat treatment process are optimized, the heat treatment quenching temperature is 960-1000 DEG C, the structure transformation austenite maximization can be achieved, the martensite content in the steel can be increased after quenching quenching, and the strength, toughness and plasticity of the steel can be improved; and then tempering, straightening and stress relief annealing are carried out, and finally the mechanical property of the 1.4104 flat steel completely meets the material standard requirement. Compared with the prior art, the invention has the following advantages: (1) through component optimization, strong austenite is added to form element nitrogen (0.0500%), ferrite forming elements such as silicon, chromium, aluminum and the like are reduced, the martensite content in the steel is increased after heat treatment quenching, and the hardness and strength in the steel are further enhanced; heat treatment cost is reduced, and production efficiency is improved; and (3) after heat treatment, the hardness (HBW) deviation of the whole steel is not greater than 15 HB, and the whole steel is relatively uniform.

Description

Technical Field

[0001] The invention belongs to the technical field of heat treatment of metal materials, and in particular relates to a quenching and tempering method for 1.4104 stainless steel flat steel. Background Art

[0002] 1.4104 steel is the main material for mechanical electro-hydraulic control valves in the coal mining industry. Electro-hydraulic control valves made of this material are mainly imported. Mechanical electro-hydraulic control valves in the coal mining industry mainly work in severe vibration, high pressure, high humidity and harsh environments for a long time. The stainless steel used in electro-hydraulic control valves is required to have the characteristics of high strength, good plasticity, small anisotropy and high processing precision. At present, domestic coal mining industry equipment has turned to intelligent, unmanned and automated technology upgrades and transformations, and there is a large demand for this material. However, the high content of this steel body makes the steel brittle. After quenching and tempering, the mechanical properties such as elongation after fracture, cross-sectional shrinkage, and impact toughness are more prominent, and re-quenching and tempering are carried out many times. As a result, the production cost of the product is high and the delivery cycle is long, which has a serious impact on the normal delivery of the product and the equipment upgrade of the industry. Summary of the invention

[0003] The invention discloses a quenching and tempering method for 1.4104 stainless steel flat steel, and aims to develop a production method for high-end stainless steel 1.4104 for a new generation of hydraulic support electro-hydraulic control valves, which has mechanical properties that meet standard requirements, low cost, high production efficiency, and accelerates equipment upgrading and transformation.

[0004] The technical solution of the present invention is as follows:

[0005] 1.1.4104 stainless steel flat steel production process: composition optimization + (EAF + LF + VOD) smelting + injection molding (ingot 2.1t) → rolling square billet → forging flat steel (125mm×135mm~152mm×152mm) → finished product annealing → desktop furnace (quenching + tempering) quenching and tempering heat treatment → straightening → stress relief annealing → finished product.

[0006] 2. The specific production process steps are as follows:

[0007] ⑴Smelting steel ingots

[0008] ① Chemical composition of steel ingot (mass fraction, %): carbon: 0.10-0.17, manganese not more than 1.50, silicon not more than 1.00, sulfur: 0.15-0.25, phosphorus not more than 0.040, chromium: 15.90-18.00, molybdenum: 0.20-0.60, nickel not more than 0.60, nitrogen: 0.0400-0.0600, the rest are iron and unavoidable impurity elements.

[0009] ② Use electric furnace EAF+LF+VOD to smelt steel ingots and cast 2.1t steel ingots to ensure internal purity and uniform composition.

[0010] ⑵Forged flat steel

[0011] ① After the steel ingot is heated and fired, the 850 rolling mill is used to roll the square billet.

[0012] ② After the billet is heated and evenly heated, it is forged into finished products with specifications of 125mm×135mm~152mm×152mm using a 1000t precision forging machine.

[0013] ⑶ Flat steel annealing + tempering treatment

[0014] ① The finished flat steel is annealed in a table furnace, heated to 30℃~50℃ above Ac1 with the furnace, kept warm for not less than 8h, then slowly cooled to below 650℃, taken out of the furnace, and air-cooled;

[0015] ② After annealing, the flat steel is subjected to quenching heat treatment in a table furnace at a quenching temperature of 950℃~1000℃;

[0016] ③After the quenching and heat preservation of the flat steel is completed, the material is quickly discharged and enters the quenching tank to be cooled by oil cooling / water-air alternating time control. The surface temperature of the flat steel is not higher than 230℃, and air cooling is used;

[0017] ④ After quenching, the flat steel is tempered in a table furnace at a tempering temperature of 650℃~680℃;

[0018] ⑤After the tempering and insulation of the flat steel is completed, it is quickly discharged and air-cooled.

[0019] ⑷ Flat steel straightening + stress relief annealing

[0020] ① The flat steel is bent and deformed due to quenching. After tempering, it needs to be straightened to ensure the straightness of the flat steel.

[0021] ② After straightening, the flat steel is subjected to stress relief annealing in a table furnace, with a stress relief tempering temperature of 600℃~640℃, and air cooling is adopted after the flat steel is taken out of the furnace;

[0022] ③After the flat steel is heat treated, the dimensions shall be checked and the dimensions shall meet the contract requirements.

[0023] 3. Standard requirements for mechanical properties of flat steel after quenching and tempering

[0024] ⑴ Mechanical properties

[0025] Flat steel delivery hardness (HBW): 220~260,

[0026] The mechanical properties of the samples after heat treatment shall comply with the requirements of Table 1.

[0027] Table 1

[0028]

[0029] ⑵ The qualified level of non-metallic inclusions shall comply with the requirements of Table 2.

[0030] Table 2

[0031]

[0032]

[0033] The innovative features of the present invention are as follows:

[0034] By optimizing the composition and tempering heat treatment process, the heat treatment quenching temperature is between 960℃ and 1000℃, which can maximize the transformation of austenite. After rapid quenching, the martensite content in the steel can be increased, which can improve the strength and toughness of the steel. After that, tempering + straightening + stress relief annealing are used, and finally the mechanical properties of 1.4104 flat steel fully meet the material standard requirements.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] ⑴Through composition optimization, strong austenite-forming element nitrogen (0.0500%) is added, while ferrite-forming elements such as silicon, chromium, and aluminum are reduced, and the martensite content in the steel is increased after heat treatment and quenching, further enhancing the hardness and strength of the steel;

[0037] (2) By applying this technical solution, even if a traditional heating furnace is used for quenching and tempering of steel, the mechanical properties can meet the requirements of the standard quenched and tempered state 1.4104, and the values ​​are stable and fluctuating;

[0038] ⑶Reduce heat treatment costs and improve production efficiency;

[0039] ⑷ After heat treatment, the hardness (HBW) deviation of the entire steel is no more than 15HB, which is relatively uniform. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below with reference to the embodiments.

[0041] Examples 1 to 3 adopt the same process flow: composition optimization + (EAF + LF + VOD) smelting + injection molding (ingot 2.1t) → rolling square billet → forging flat steel (125mm×135mm~152mm×152mm) → finished product annealing → desktop furnace (quenching + tempering) tempering heat treatment → straightening → stress relief annealing → finished product.

[0042] 1. Use electric furnace EAF+LF+VOD for smelting and mold 2.1t steel ingot; control the chemical composition according to the target value to ensure the purity and uniformity of the steel ingot.

[0043] 2. Steel ingots are forged into products;

[0044] ① After the steel ingot is heated and thoroughly fired, the 850 rolling mill is used to roll the square billet.

[0045] ② After the billet is heated and evenly heated, a 1000t precision forging machine is used to forge the flat steel product.

[0046] 3. Finished flat steel annealing + quenching + tempering heat treatment

[0047] Step 1: After rolling, the finished flat steel is annealed in a table furnace.

[0048] Step 2: The annealed flat steel is subjected to quenching heat treatment in a table furnace;

[0049] Step 3: After the quenching and heat preservation of the flat steel, it is quickly discharged and enters the quenching tank for cooling by oil cooling / water-air alternating time control method and air cooling;

[0050] Step 4: The quenched flat steel is tempered in a table furnace;

[0051] Step 5: After the tempering and heat preservation of the flat steel is completed, the material is quickly discharged and air-cooled;

[0052] 4. Flat steel straightening + stress relief annealing

[0053] ① Flat steel is bent and deformed due to quenching, and needs to be straightened after tempering to ensure the straightness of the bar.

[0054] ② The straightened flat steel is subjected to stress relief annealing in a tabletop furnace;

[0055] ③After the flat steel is heat treated, the dimensions are checked to ensure that they meet the contract requirements.

[0056] Example 1

[0057] 1. Ingot smelting process

[0058] The chemical composition test results of the steel ingot are shown in Table 3.

[0059] 2. Steel ingot forging process

[0060] The size of the forged product is 125mm×135mm flat steel.

[0061] 3. Finished flat steel annealing + quenching + tempering heat treatment

[0062] Step 1: The finished flat steel is annealed in a table furnace at 800°C, with a holding temperature deviation of ±10°C for 10 hours, and then slowly cooled to no higher than 650°C at a rate of no more than 50°C / h, and then air-cooled.

[0063] Step 2: After annealing, the flat steel is subjected to quenching heat treatment in a table furnace, with a quenching temperature of 980°C, a holding temperature deviation of ±10°C, and a holding temperature of 3h10min;

[0064] Step 3: The flat steel is quenched by water-air alternating time-controlled cooling, the surface temperature of the flat steel is not higher than 220℃, and air cooling;

[0065] Step 4: After quenching, the flat steel is tempered in a table furnace at a tempering temperature of 665°C, a holding temperature deviation of ±10°C, and a holding time of 4.5 hours;

[0066] 4. Flat steel stress relief annealing

[0067] The straightened flat steel is subjected to stress relief annealing in a table furnace, with a stress relief annealing temperature of 620°C, a holding temperature deviation of ±10°C, and a holding time of 4 hours;

[0068] 5. Test results

[0069] ① Mechanical properties test results are shown in Table 4.

[0070] ②The test results of non-metallic inclusions are shown in Table 5.

[0071] Example 2

[0072] 1. Ingot smelting process

[0073] The chemical composition test results of the steel ingot are shown in Table 3.

[0074] 2. Steel ingot forging process

[0075] The size of the forged product is 125mm×135mm flat steel.

[0076] 3. Finished flat steel annealing + quenching + tempering heat treatment

[0077] Step 1: The finished flat steel is annealed in a table furnace at 800°C, with a holding temperature deviation of ±10°C for 10 hours, and then slowly cooled to 650°C at a rate of no more than 50°C / h, and air-cooled.

[0078] Step 2: After annealing, the flat steel is quenched in a table furnace at a quenching temperature of 990°C, with a holding temperature deviation of ±10°C and a holding temperature of 3h.

[0079] Step 3: The flat steel is quenched by water-air alternating time-controlled cooling, the flat steel surface temperature is not higher than 230℃, air cooling;

[0080] Step 4: After quenching, the flat steel is tempered in a table furnace at a tempering temperature of 665°C, a holding temperature deviation of ±10°C, and a holding time of 4.5 hours;

[0081] 4. Flat steel stress relief annealing

[0082] The straightened flat steel is subjected to stress relief annealing in a table furnace, with a stress relief annealing temperature of 620°C, a holding temperature deviation of ±10°C, and a holding time of 4 hours;

[0083] 5. Test results

[0084] ① Mechanical properties test results are shown in Table 4.

[0085] ②The test results of non-metallic inclusions are shown in Table 5.

[0086] Example 3

[0087] 1. Ingot smelting process

[0088] The chemical composition test results of the steel ingot are shown in Table 3.

[0089] 2. Steel ingot forging process

[0090] The size of the forged product is 125mm×135mm flat steel.

[0091] 3. Finished flat steel annealing + quenching + tempering heat treatment

[0092] Step 1: The finished flat steel is annealed in a table furnace at 800°C, with a holding temperature deviation of ±10°C for 10 hours, and then slowly cooled to 650°C at a rate of no more than 50°C / h, and air-cooled.

[0093] Step 2: After annealing, the flat steel is quenched in a table furnace at a quenching temperature of 1000°C, a holding temperature deviation of ±10°C, and a holding temperature of 3 hours;

[0094] Step 3: The flat steel is quenched by water-air alternating time-controlled cooling, the surface temperature of the flat steel is not higher than 220℃, and air cooling;

[0095] Step 4: After quenching, the flat steel is tempered in a table furnace at a tempering temperature of 665°C, a holding temperature deviation of ±10°C, and a holding temperature of 4 hours;

[0096] 4. Flat steel stress relief annealing

[0097] The straightened flat steel is subjected to stress relief annealing in a table furnace, with a stress relief annealing temperature of 620°C, a holding temperature deviation of ±10°C, and a holding time of 4 hours;

[0098] 5. Test results

[0099] ① Mechanical properties test results are shown in Table 4.

[0100] ②The test results of non-metallic inclusions are shown in Table 5.

[0101] The chemical composition test results of Examples 1 to 3 are shown in Table 3.

[0102] Table 3

[0103]

[0104] The room temperature mechanical properties test results of Examples 1 to 3 are shown in Table 4.

[0105] Table 4

[0106]

[0107] The non-metallic inclusion inspection results of Examples 1 to 3 are shown in Table 5.

[0108] Table 5

[0109]

Claims

1. A method for quenching and tempering 1.4104 stainless steel flat steel, characterized in that: The production process of 1.4104 stainless steel flat steel is as follows: composition optimization + smelting by electric furnace EAF+LF+VOD + mold injection ingot → rolling square billet → forging flat steel → finished product annealing → desktop furnace quenching + tempering heat treatment → straightening → stress relief annealing → finished product; ⑴Smelting steel ingots ① Optimize the chemical composition of steel ingot by mass percentage: carbon: 0.10% to 0.17%, manganese not more than 1.50%, silicon not more than 1.00%, sulfur: 0.15% to 0.25%, phosphorus not more than 0.040%, chromium: 15.90% to 18.00%, molybdenum: 0.20% to 0.60%, nickel not more than 0.60%, nitrogen: 0.0400% to 0.0600%, and the rest are iron and unavoidable impurity elements; ② Use electric furnace EAF+LF+VOD to smelt steel ingots and cast 2.1t steel ingots to ensure internal purity and uniform composition; ⑵Forged flat steel ① After the steel ingot is heated and fired, the 850 rolling mill is used to roll the square billet; ② After the billet is heated and evenly heated, it is forged into finished products with specifications of 125mm×135mm~152mm×152mm using a 1000t precision forging machine; ⑶ Flat steel annealing + tempering treatment ① The finished flat steel is annealed in a table furnace, heated to 30℃~50℃ above Ac1 with the furnace, kept warm for not less than 8h, then slowly cooled to below 650℃, taken out of the furnace, and air-cooled; ② After annealing, the flat steel is subjected to quenching heat treatment in a table furnace at a quenching temperature of 950℃~1000℃; ③After the quenching and heat preservation of the flat steel is completed, the material is quickly discharged and enters the quenching tank to be cooled by oil cooling / water-air alternating time control. The surface temperature of the flat steel is not higher than 230℃, and air cooling is used; ④ After quenching, the flat steel is tempered in a table furnace at a tempering temperature of 650℃~680℃; ⑤After the tempering and heat preservation of the flat steel is completed, the material is quickly discharged and air-cooled; ⑷ Flat steel straightening + stress relief annealing ① The flat steel is bent and deformed due to quenching. After tempering, it needs to be straightened to ensure the straightness of the flat steel. ② After straightening, the flat steel is subjected to stress relief annealing in a table furnace, with a stress relief tempering temperature of 600℃~640℃, and air cooling is adopted after the flat steel is taken out of the furnace; ③After the flat steel is heat treated, the dimensions shall be checked and the dimensions shall meet the contract requirements.

2. A method for quenching and tempering 1.4104 stainless steel flat steel according to claim 1, characterized in that: (1) The test results of chemical composition of steel ingots are shown in Table 3; Table 3 (2) The size of the steel ingot forging product is 125mm×135mm flat steel; ⑶ Finished flat steel annealing + quenching + tempering heat treatment: ① The finished flat steel is annealed in a table furnace at 800℃, with a holding temperature deviation of ±10℃ for 10h, and then slowly cooled to no higher than 650℃ at a rate of no more than 50℃ / h before being taken out of the furnace and air-cooled; ② After annealing, the flat steel is subjected to quenching heat treatment in a table furnace, with a quenching temperature of 980°C, a holding temperature deviation of ±10°C, and a holding temperature of 3h10min; ③ The flat steel quenching adopts water-air alternating time-controlled cooling, the flat steel surface temperature is not higher than 220℃, air cooling; ④ After quenching, the flat steel is tempered in a table furnace at a tempering temperature of 665°C, a holding temperature deviation of ±10°C, and a holding time of 4.5 hours; ⑷ Flat steel stress relief annealing The straightened flat steel is subjected to stress relief annealing in a table furnace, with a stress relief annealing temperature of 620°C, a holding temperature deviation of ±10°C, and a holding time of 4 hours; ⑸Test results ① Mechanical properties test results are shown in Table 4; Table 4 ②The test results of non-metallic inclusions are shown in Table 5. Table 5 3. A method for quenching and tempering 1.4104 stainless steel flat steel according to claim 1, characterized in that: (1) The test results of chemical composition of steel ingots are shown in Table 6; Table 6 (2) The size of the steel ingot forging product is 125mm×135mm flat steel; ⑶ Finished flat steel annealing + quenching + tempering heat treatment: ① The finished flat steel is annealed in a table furnace at 800℃, with a holding temperature deviation of ±10℃ for 10h, and then slowly cooled to no higher than 650℃ at a rate of no more than 50℃ / h before being taken out of the furnace and air-cooled; ② After annealing, the flat steel is quenched in a table furnace at a quenching temperature of 990°C, a holding temperature deviation of ±10°C, and a holding temperature of 3h; ③ The flat steel quenching adopts water-air alternating time-controlled cooling, the flat steel surface temperature is not higher than 230℃, air cooling; ④ After quenching, the flat steel is tempered in a table furnace at a tempering temperature of 665°C, a holding temperature deviation of ±10°C, and a holding time of 4.5 hours; ⑷ Flat steel stress relief annealing The straightened flat steel is subjected to stress relief annealing in a table furnace, with a stress relief annealing temperature of 620°C, a holding temperature deviation of ±10°C, and a holding time of 4 hours; ⑸Test results ① Mechanical properties test results are shown in Table 7; Table 7 ②The test results of non-metallic inclusions are shown in Table 8. Table 8 4. A method for quenching and tempering 1.4104 stainless steel flat steel according to claim 1, characterized in that: (1) The test results of chemical composition of steel ingots are shown in Table 9; Table 9 (2) The size of the steel ingot forging product is 125mm×135mm flat steel; ⑶ Finished flat steel annealing + quenching + tempering heat treatment: ① The finished flat steel is annealed in a table furnace at 800℃, with a holding temperature deviation of ±10℃ for 10h, and then slowly cooled to no higher than 650℃ at a rate of no more than 50℃ / h before being taken out of the furnace and air-cooled; ② After annealing, the flat steel is quenched in a table furnace at a quenching temperature of 1000°C, a holding temperature deviation of ±10°C, and a holding temperature of 3h; ③ The flat steel quenching adopts water-air alternating time-controlled cooling, the flat steel surface temperature is not higher than 220℃, air cooling; ④ After quenching, the flat steel is tempered in a table furnace at a tempering temperature of 665°C, a holding temperature deviation of ±10°C, and a holding time of 4.5 hours; ⑷ Flat steel stress relief annealing The straightened flat steel is subjected to stress relief annealing in a table furnace, with a stress relief annealing temperature of 620°C, a holding temperature deviation of ±10°C, and a holding time of 4 hours; ⑸Test results ① Mechanical properties test results are shown in Table 10; Table 10 ②The test results of non-metallic inclusions are shown in Table 11. Table 11

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