A method for refining stainless steel for engine high pressure common rail

Abstract

The present invention belongs to the field of metallurgy, and is a method for refining stainless steel for engine high-pressure common rail, characterized in that: step 1: adjusting the chemical composition of stainless steel for high-pressure common rail except S and Al content to the target requirement in LF refining furnace, that is, the mass percentage of chemical composition of stainless steel for high-pressure common rail in claim 1, feeding 1-2m / t calcium wire for calcium treatment; step 2: adding quartz sand to control the slag basicity CaO / SiO2 to 1.2-1.5, then adding 1.2-1.5Kg / t magnesium balls, and feeding sulfur wire to adjust S content to the target requirement after slag adjustment. The present invention can make the coarseness and fineness of non-metallic inclusions A in stainless steel for high-pressure common rail not more than 1.5 level, and the coarseness and fineness of B, C, D and DS are all not more than 1.0 level, and the leakage rate caused by the incompatibility of non-metallic inclusions before assembling stainless steel for high-pressure common rail is reduced from 0.3% to 0.

Description

Technical Field

[0001] The invention belongs to the field of metallurgy and relates to a method for refining stainless steel for engine high-pressure common rail. Background Art

[0002] High-pressure common rail electronic fuel injection system has the comprehensive performance of making diesel or gasoline engines achieve high power, low fuel consumption, low emissions, low noise, etc. With the rapid development of the automobile industry towards low energy consumption and high environmental protection, high-pressure common rail electronic fuel injection system is widely used in modern high-tech automobile engines.

[0003] The high-pressure common rail is a high-pressure fuel accumulator in automobile engines and an indispensable and important component in the electronically controlled fuel injection system of automobile engines. It plays the role of distributing the high-pressure fuel provided by the high-pressure fuel pump to each injector. The fuel pressure in the high-pressure common rail exceeds 160MPa.

[0004] The high-pressure common rail works under high pressure, high heat and high humidity environment, and the intrinsic quality requirements of the stainless steel used to make it are very strict. Otherwise, it will cause fuel leakage, leading to engine failure and various accidents.

[0005] The quality problems of stainless steel used in high-pressure common rails are mainly manifested in that the internal non-metallic inclusions are all higher than level 1.5, especially the Al2O3 brittle inclusions exceed level 3. During the inspection before the high-pressure common rail assembly, the leakage rate is as high as 0.3%.

[0006] In order to solve the quality problem of stainless steel for high-pressure common rail, the present invention provides a method for refining stainless steel for high-pressure common rail of an engine, which can make the coarseness series of non-metallic inclusions A in the stainless steel for high-pressure common rail not greater than 1.5, and the coarseness series of B, C, D and DS not greater than 1.0, and the leakage rate caused by the incompatibility of non-metallic inclusions before assembling the stainless steel for high-pressure common rail is reduced from 0.3% to 0. Summary of the invention

[0007] The purpose of the present invention is to provide a method for refining stainless steel for engine high pressure common rail in view of the above problems.

[0008] The object of the present invention is achieved by: a method for refining stainless steel for engine high-pressure common rail, wherein the mass percentage of the chemical composition of the stainless steel for high-pressure common rail is as follows: C≤0.03, Si≤1.00, Mn≤2.00, P 0.020-0.040, S: 0.015-0.030, Cr: 18.00-19.50, Ni: 8.00-10.50, Al≤0.008, N≤0.08, and the rest is Fe and unavoidable impurities.

[0009] A method for refining stainless steel for engine high-pressure common rail, characterized in that it comprises the following steps: step 1: adjusting the chemical composition of the stainless steel for high-pressure common rail except the S and Al content to the target requirements, that is, the mass percentage of the chemical composition of the stainless steel for high-pressure common rail in claim 1, in an LF refining furnace, and feeding 1-2 m / t of metal calcium wire for calcium treatment; step 2: adding quartz sand to control the slag basicity CaO / SiO2 to 1.2-1.5, then adding 1.2-1.5 kg / t of magnesium balls, and after slag adjustment, feeding a sulfur wire to adjust the S content to the target requirements.

[0010] In step 1, the diameter of the metal calcium wire is ∮9 mm, the core weight is 60 g / m, and the Ca content is 97%.

[0011] The MgO content of the magnesium ball in step 2 is 72%.

[0012] The beneficial effects of the present invention are as follows: the present invention can make the non-metallic inclusion A coarseness series not greater than 1.5 level, the coarseness series B, C, D and DS not greater than 1.0 level in the stainless steel for high-pressure common rail, and the leakage rate caused by the incompatibility of non-metallic inclusions before the stainless steel for high-pressure common rail is assembled is reduced from 0.3% to 0. DETAILED DESCRIPTION

[0013] High-pressure common rails work under high pressure, high heat and high humidity, and the internal quality requirements of the stainless steel used to make them are very strict, otherwise it will cause fuel leakage, leading to engine failure and various accidents. The quality problems of stainless steel used in high-pressure common rails are mainly manifested in that the internal non-metallic inclusions are higher than level 1.5, especially Al2O3 brittle inclusions exceeding level 3. The leakage rate of the high-pressure common rails is as high as 0.3% during the inspection before assembly.

[0014] In the LF refining furnace, the chemical composition of the stainless steel for high-pressure common rail (except S and Al content) is adjusted to the target requirements, and 1-2m / t of metal calcium wire (diameter ∮9mm, core weight 60g / m, Ca content 97%) is fed for calcium treatment; quartz sand is added to control the slag basicity (CaO / SiO2) at 1.2-1.5, and then 1.2-1.5Kg / t of magnesium balls (MgO content 72%) are added. After slag adjustment, the sulfur wire is fed to adjust the S content to the target requirement. While reducing non-metallic inclusions in the steel, it not only improves the sulfur recovery rate, but also reduces the C increase of the molten steel when the LF refining furnace is powered on and the temperature drop of the molten steel during casting.

[0015] The present invention can make the non-metallic inclusions in the stainless steel for high-pressure common rail A not greater than 1.5, the B, C, D and DS not greater than 1.0, and the leakage rate caused by the non-metallic inclusions before the stainless steel for high-pressure common rail is assembled is reduced from 0.3% to 0. The specific scheme is as follows.

[0016] Ⅰ The mass percentage of chemical composition of stainless steel for high pressure common rail: C≤0.03, Si≤1.00, Mn≤2.00, P:0.020-0.040, S:0.015-0.030, Cr: 18.00-19.50, Ni:8.00-10.50, Al≤0.008, N≤0.08, and the rest are Fe and unavoidable impurities.

[0017] Ⅱ In the LF refining furnace, the chemical composition of the stainless steel for high pressure common rail (except S and Al content) is adjusted to the target requirements, and 1-2m / t of metal calcium wire (diameter ∮9mm, core weight 60g / m, Ca content 97%) is fed for calcium treatment.

[0018] III Add quartz sand to control the slag basicity (CaO / SiO2) at 1.2-1.5, then add 1.2-1.5 kg / t magnesium balls (MgO content 72%), and after slag adjustment, feed it into the sulfur line to adjust the S content to the target requirement.

[0019] The specific implementation of a method for refining stainless steel for engine high-pressure common rail is described in detail below in conjunction with embodiments, but the specific implementation of the present invention is not limited to the following embodiments.

[0020] Embodiment 1

[0021] This embodiment is carried out in a 90-ton LF refining furnace, and the chemical composition mass percentage is: C≤0.03, Si≤1.00, Mn≤2.00, P 0.020-0.040, S: 0.015-0.030,

[0022] Cr: 18.00-19.50, Ni: 8.00-10.50, Al≤0.008, N≤0.08, and the rest are Fe and unavoidable impurities.

[0023] Ⅰ 86t of stainless steel liquid for high pressure common rail was adjusted to the target requirements in LF refining furnace in terms of chemical composition by mass percentage (except S and Al content): C: 0.015, Si: 0.40, Mn: 1.30, P: 0.035, S: 0.005, Cr: 18.12, Ni: 8.10, Al: 0.01, N: 0.06, and the rest were Fe and unavoidable impurities.

[0024] 90m / t metal calcium wire (diameter ∮9mm, core weight 60g / m, Ca content 97%) was fed for calcium treatment.

[0025] Ⅱ Add 0.22t quartz sand (SiO2 content 97%) to control the slag basicity (CaO / SiO2) at 1.4, then add 0.11t magnesium balls (MgO content 72%), and after slag adjustment, feed 150m sulfur wire (∮13mm, core weight 200g / m, S content 99%) to adjust the S content to the target requirement.

[0026] Ⅲ Finished product chemical composition mass percentage: C: 0.016, Si: 0.38, Mn: 1.29, P: 0.035, S: 0.026, Cr: 18.11, Ni: 8.10, Al: 0.003, N: 0.059, the rest are Fe and unavoidable impurities.

[0027] The high-pressure common rail of this furnace is made of stainless steel. The non-metallic inclusions A are of grade 1.0, B and C are of grade 0, D and DS are of grade 0.5. The leakage rate caused by the mismatch of non-metallic inclusions before assembly is 0.

[0028] Embodiment 2

[0029] This example was carried out on a 180-ton LF refining furnace, and the chemical composition mass percentage is:

[0030] C≤0.03 Si≤1.00 Mn≤2.00 P: 0.020-0.040 S: 0.015-0.030

[0031] Cr: 18.00-19.50 Ni: 8.00-10.50 Al≤0.008 N≤0.08, the rest are Fe and inevitable impurities.

[0032] Ⅰ 185t of stainless steel liquid for high pressure common rail is adjusted to the target requirements in LF refining furnace in terms of chemical composition mass percentage (except S and Al content): C: 0.020, Si: 0.45, Mn: 1.51, P: 0.037, S: 0.002, Cr: 18.20, Ni: 8.15, Al: 0.007, N: 0.063, and the rest are Fe and unavoidable impurities.

[0033] Calcium treatment was performed by feeding metal calcium wire 336 m / t (diameter ∮9 mm, core weight 60 g / m, Ca content 97%).

[0034] Ⅱ Add 0.58t of quartz sand (SiO2 content 97%) to control the slag basicity (CaO / SiO2) at 1.3, then add 0.27t of magnesium balls (MgO content 72%), and after slag adjustment, feed 330m of sulfur wire (∮13mm, core weight 200g / m, S content 99%) to adjust the S content to the target requirement.

[0035] Ⅲ The chemical composition of the finished product by mass percentage: C: 0.021, Si: 0.43, Mn: 1.50, P: 0.037, S: 0.027, Cr: 18.18, Ni: 8.15, Al: 0.003, N: 0.062, and the rest are Fe and unavoidable impurities.

[0036] The high-pressure common rail of this furnace is made of stainless steel. The non-metallic inclusions A coarseness series are 0.5 level, B and C coarseness series are 0 level, D coarseness series and DS are 0.5 level. The leakage rate caused by the incompatibility of non-metallic inclusions before assembly is 0.

[0037] The above description is only a specific embodiment of the present invention, but the structural features of the protection scope of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are included in the patent scope of the present invention.

Claims

1. A method for refining stainless steel for engine high pressure common rail, characterized in that: The mass percentage of chemical composition of stainless steel for high pressure common rail: C: 0.016-0.03, Si: 0.38-1.00, Mn: 1.29-2.00, P 0.020-0.040, S: 0.015-0.030, Cr: 18.00-19.50, Ni: 8.00-10.50, Al: 0.003-0.008, N≤0.08, the rest is Fe and unavoidable impurities; The method for refining stainless steel for engine high-pressure common rail comprises the following steps: Step 1: In the LF refining furnace, the chemical composition of the high pressure common rail stainless steel except the S and Al content is adjusted to the target requirements, and 1-2m / t of calcium is fed into the metal calcium line for calcium treatment; Step 2: Add quartz sand to control the slag basicity CaO / SiO2 at 1.2-1.5, then add 1.2-1.5 kg / t magnesium balls, and after slag adjustment, feed the sulfur line to adjust the S content to the target requirement; In step 1, the diameter of the metal calcium wire is ∮9 mm, the core weight is 60 g / m, and the Ca content is 97%; The MgO content of the magnesium ball in step 2 is 72%; Through the above method, the non-metallic inclusions A in the stainless steel for high pressure common rail are not greater than level 1.5 in coarseness and fineness, and the coarseness and fineness of B, C, D and DS are all not greater than level 1.0.