Production method of 1Cr17Ni2 crane shaft forging

Abstract

The invention discloses a production method of a 1Cr17Ni2 crane shaft forge piece. The production method sequentially comprises the steps of heating before forging, forging, cooling after forging, rough machining, heat treatment and finish machining. The forging is made of 1Cr17Ni2 steel, and the 1Cr17Ni2 steel comprises, by mass, 0.12%-0.2% of C, smaller than or equal to 1% of Mn, smaller than or equal to 0.04% of P, smaller than or equal to 0.03% of S, smaller than or equal to 1% of Si, 15%-18% of Cr, 2.2%-3% of Ni and the balance Fe and inevitable impurities. The production method of the 1Cr17Ni2 crane shaft forge piece is based on 1Cr17Ni2 steel, and the mechanical performance of the forge piece is improved by strictly controlling the content of element carbon and nickel in the steel for forging; blank cracking caused by heating stress is effectively avoided through stepped heating, the forging piece obtains good mechanical performance through the appropriate forging ratio, excessive growth and nonuniformity of crystal grains are prevented, and the cooling process after forging is regulated and controlled to prevent cooling stress caused by room temperature cooling. The forging is a combined forging, the combined forging is divided into a plurality of single forgings in the rough machining step, the production efficiency is high, and the mechanical properties of the produced single forgings are similar.

Description

Technical Field

[0001] The invention relates to the technical field of forging production, and in particular to a production method of a 1Cr17Ni2 crane shaft forging. Background Art

[0002] Domestic grade 1Cr17Ni2 is a type of martensitic stainless steel with good strength and toughness. It is generally used in the production of nitric acid and acetic acid and in light industry, textile and other industries that require both strength, toughness and corrosion resistance of shafts, piston rods, pumps and other parts.

[0003] Low alloy steel and ordinary steel with a carbon content of about 0.2% are susceptible to cracks during pre-forging heating, post-breaking cooling, quenching and tempering due to their own elemental composition; Cr17Ni2 steel is a low alloy steel with a C content of no more than 0.2%; using Cr17Ni2 steel to produce crane shafts must not only meet the customer's mechanical performance requirements, but also control cracks within the customer's allowable range. Summary of the invention

[0004] The object of the present invention is to provide a method for producing a 1Cr17Ni2 crane shaft forging, wherein the produced forging is not prone to cracks during the production process.

[0005] In order to achieve the above technical effects, the technical solution of the present invention is: a production method of 1Cr17Ni2 crane shaft forgings, including the steps of pre-forging heating, forging, post-forging cooling, rough machining, heat treatment and finishing; the forgings are made of 1Cr17Ni2 steel, and the element composition of the 1Cr17Ni2 steel is as follows by mass percentage: C: 0.12%~0.2%, Mn:≤1%, P:≤0.04%, S:≤0.03%, Si:≤1%, Cr:15%~18%, Ni:2.2%~3%, the balance is Fe and unavoidable impurities. Further, the mass percentage of C is 0.12%~0.16%, and the mass percentage of Ni is 2.5%~3%. Specifically, no additional C and Ni are added during the production of steel billets for forging steel, and the contents of C and Ni in other steel billet alloy raw materials are controlled.

[0006] The preferred technical solution is that the pre-forging heating step includes: After the forging is loaded into the furnace at room temperature, it is heated to 290-310° C. and kept warm for 0.2-0.3 h / 100 mm according to the effective thickness of the forging; then it is heated to 590-610° C. and kept warm for 0.2-0.3 h / 100 mm according to the effective thickness of the forging; then it is heated to 990-1010° C. and kept warm for 0.3-0.4 h / 100 mm according to the effective thickness of the forging; finally it is heated to 1170-1190° C. and kept warm for 0.4-0.6 h / 100 mm according to the effective thickness of the forging. Furthermore, after the forging is loaded into the furnace at room temperature, it is heated to 295-305°C and kept warm for 0.25-0.3h / 100mm according to the effective thickness of the forging; then it is heated to 595-605°C and kept warm for 0.25-0.3h / 100mm according to the effective thickness of the forging; then it is heated to 995-1005°C and kept warm for 0.35-0.4h / 100mm according to the effective thickness of the forging; finally it is heated to 1175-1185°C and kept warm for 0.5-0.6h / 100mm according to the effective thickness of the forging.

[0007] The preferred technical solution is that the pre-forging heating step consists of four step-wise heatings, wherein: the heating rates of the first and second heatings of the forging are no more than 80°C / h, and the heating rates of the third and fourth heatings of the forging are no more than 100°C / h. Furthermore, the heating rates of the first and second heatings of the forging are 70-80°C / h, and the heating rates of the third and fourth heatings of the forging are 90-100°C / h.

[0008] The preferred technical solution is that the heating rate of the forging during the first and second heating is lower than the heating rate of the forging during the third and fourth heating. Furthermore, the heating rate of the forging during the first and second heating is 80°C / h, and the heating rate of the forging during the third and fourth heating is 100°C / h.

[0009] A preferred technical solution is that the initial forging temperature of the forging in the forging step is 1140-1150°C, and the final forging temperature of the forging in the forging step is not less than 900°C.

[0010] The preferred technical solution is that the forging step includes two upsetting steps and two drawing steps which are performed alternately in sequence, and in the two upsetting steps and the two drawing steps: The first upsetting forging ratio is 1.69~1.89; The first drawing forging ratio is 1.58~1.78; The second upsetting forging ratio is 1.35~1.46; The second drawing forging ratio is 4.85~5.05.

[0011] Furthermore, the first upsetting forging ratio is 1.7~1.85; The first drawing and forging ratio is 1.6~1.76; The second upsetting forging ratio is 1.37~1.46; The second drawing forging ratio is 4.87~5.03.

[0012] The preferred technical solution is that the post-forging cooling step comprises: After the forging step is completed, the forging is kept at a temperature of 590-610°C for 0.4-0.5h / 100mm of the effective thickness of the forging, and then cooled to room temperature at a cooling rate of 20-30°C / h. Further, the forging is cooled to room temperature at a cooling rate of 20°C / h.

[0013] The preferred technical solution is that the heat treatment step includes sequential quenching and tempering steps; the quenching step is: After the forging is heated to 790-810°C at a heating rate of no more than 100°C / h, it is kept warm for 1.3-1.4h / 100mm according to the effective thickness of the forging; then the forging is heated to 1010-1030°C at a heating rate of no more than 100°C / h, kept warm for 3.9-4.0h / 100mm according to the effective thickness of the forging, and finally oil quenched. Further, after the forging is heated to 790-810°C at a heating rate of 90-100°C / h, it is kept warm for 1.3-1.4h / 100mm according to the effective thickness of the forging; then the forging is heated to 1010-1030°C at a heating rate of no more than 90-100°C / h, kept warm for 3.9-4.0h / 100mm according to the effective thickness of the forging, and finally oil quenched.

[0014] The preferred technical solution is that the tempering step is: The cooled forging is heated to 650-670°C at a heating rate of no more than 100°C / h, kept warm for 5.9-6.0h / 100mm of the effective thickness of the forging, and finally air-cooled. Further, the cooled forging is heated to 650-670°C at a heating rate of 90-100°C / h, kept warm for 5.9-6.0h / 100mm of the effective thickness of the forging, and finally air-cooled.

[0015] A preferred technical solution is that the forging is a composite forging, and the rough machining step divides the composite forging into multiple single forgings.

[0016] The advantages and beneficial effects of the present invention are: The production method of the 1Cr17Ni2 crane shaft forging is based on 1Cr17Ni2 steel. The mechanical properties of the forging are improved by strictly controlling the contents of elemental carbon and nickel in the forging steel. The step-by-step heating effectively avoids cracking of the billet caused by heating stress. The appropriate forging ratio enables the forging to obtain good mechanical properties and prevents excessive grain growth and unevenness. The post-forging cooling process is regulated to prevent cooling stress caused by room temperature cooling. The forging is a combined forging, and the rough processing step divides the combined forging into multiple single forgings, so the production efficiency is high and the mechanical properties of the multiple single forgings produced are similar. DETAILED DESCRIPTION

[0017] The specific implementation of the present invention is further described below in conjunction with the examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention, and cannot be used to limit the protection scope of the present invention.

[0018] The element composition of stainless steel with grade 1Cr17Ni2 is: C: ≤0.2%, Mn: ≤1%, P: ≤0.04%, S: ≤0.03%, Si: ≤1%, Cr: 15%~17%, Ni: 1.25%~2.5%.

[0019] The mass percentage of an element in forging steel is limited to "≤n", which means that the content of the element in the forging steel is 0~n, excluding the minimum endpoint value "0".

[0020] Upsetting forging ratio The ratio of the larger value to the smaller value of the forging length before and after upsetting is the upsetting forging ratio.

[0021] Drawing forging ratio The ratio of the larger value to the smaller value of the forging length before and after drawing is the drawing forging ratio.

[0022] Hardness Difference The hardness difference of multiple single forgings is obtained by subtracting the minimum hardness value from the maximum hardness value. The hardness difference is divided by the maximum hardness value and then multiplied by 100% to obtain the hardness difference of multiple single forgings.

[0023] Difference in yield strength at 20℃ The 20°C yield strength difference of multiple single forgings is obtained by subtracting the minimum 20°C yield strength of the maximum 20°C yield strength of the multiple single forgings from the minimum 20°C yield strength. The 20°C yield strength difference is divided by the maximum 20°C yield strength and then multiplied by 100% to obtain the 20°C yield strength difference of the multiple single forgings.

[0024] Difference in tensile strength at 20℃ The 20℃ tensile strength difference of multiple single forgings is obtained by subtracting the minimum 20℃ tensile strength of the maximum 20℃ tensile strength of the multiple single forgings from the minimum 20℃ tensile strength. The 20℃ tensile strength difference is divided by the maximum 20℃ tensile strength and multiplied by 100% to obtain the 20℃ tensile strength difference of multiple single forgings.

[0025] 20℃ elongation difference The 20°C elongation difference of multiple single forgings is obtained by subtracting the minimum 20°C elongation value from the maximum 20°C elongation value of the multiple single forgings. The 20°C elongation difference is divided by the 20°C elongation maximum value and then multiplied by 100% to obtain the 20°C elongation difference of multiple single forgings.

[0026] Difference in impact performance at 20℃ The performance difference of the multiple single forgings at 20°C is obtained by subtracting the minimum performance value from the maximum performance value in the average value of the impact performance data of the multiple single forgings at 20°C, dividing the performance difference by the maximum performance value and multiplying it by 100% to obtain the impact performance difference of the multiple single forgings at 20°C. Example

[0027] Example 1

[0028] The measured values ​​of the chemical composition mass percentages of the production method of the 1Cr17Ni2 crane shaft forging of Example 1 are: C: 0.15%, Mn: 0.64%, P: 0.028%, S: 0.002%, Si: 0.32%, Cr: 16.5%, Ni: 2.26%, and the balance is Fe and unavoidable impurities; The production of 1Cr17Ni2 crane shaft forgings includes pre-forging heating, forging, post-forging cooling, rough machining, heat treatment and finishing: S1: After the 25-inch billet weighing 4200kg is loaded into the furnace, the furnace temperature is increased to 300℃ at a heating rate of 80℃ / h and kept at this temperature for 1.5h; then, the furnace temperature is increased to 600℃ at a heating rate of 80℃ / h and kept at this temperature for 1.5h; then, the furnace temperature is increased to 1000℃ at a heating rate of 100℃ / h and kept at this temperature for 2h; finally, the furnace temperature is increased to 1180℃ at a heating rate of 100℃ / h and kept at this temperature for 3h; S2: Take out the blank, at which time the surface temperature of the blank is 1140℃ and the core temperature is 1150℃; first perform two upsetting and one drawing operations, the 1700mm long blank is first upset to 950mm, then drawn to 1600mm, and finally upset to 1100mm; The first upsetting forging ratio is 1.79; The first drawing and forging ratio is 1.68; The second upsetting forging ratio is 1.45; S3: The forgings after the second upsetting are returned to the furnace, at which the surface temperature of the forgings is 920°C and the core temperature is 950°C; the return time is 2h and the return temperature is 1170°C; S4: Take out the forging and draw it to 5450mm, with a drawing-to-forging ratio of 4.95; S5: Finish the forgings. The surface temperature of the finished forgings is 960°C and the core temperature is 980°C. S6: Place the forging in a 600°C trolley furnace for insulation for 1.5 hours. After the insulation is completed, the forging is furnace cooled until the surface and core of the forging reach room temperature. The cooling rate of the forging is measured to be 20°C / h. S7: split the forging by sawing machine and divide the forging into 5 pieces; S8: Quenching: after the forgings are loaded into the furnace, the furnace temperature is raised to 800°C at a heating rate of 100°C / h. After being kept at this temperature for 4 hours, the furnace temperature is again raised to 1020°C at a heating rate of 100°C / h. After being kept at this temperature for 12 hours, oil quenching is performed. S9: Tempering, heating the forgings, raising the furnace temperature to 660°C at a heating rate of 100°C / h, keeping the temperature for 18h, and then air cooling; S10: Finishing of forgings.

[0029] The time taken from S1 to S7 of Example 1 is 60.2 hours.

[0030] The performance qualification requirements and test results of the 1Cr17Ni2 crane shaft forging of Example 1 are as follows: 1. Mechanical properties test qualification requirements: 20℃ yield strength Rp0.2 ≥ 635MPa, 20℃ tensile strength Rm ranges from 850MPa to 1000MPa, 20℃ elongation A ≥ 11%, 20℃ impact performance (KV) ≥ 20J.

[0031] 2. Hardness qualification requirements: 248HB-302HB; 3. Ultrasonic flaw detection qualification requirements: According to EN1023.3 CL.3 / GST.1.5.5, single defects exceeding 2.5mm shall be recorded and reported, and electric welding is not allowed.

[0032] 4. Magnetic particle inspection qualification requirements: According to EN10228-1 Class 2; GST.1.5.5, there is no surface crack.

[0033]

[0034] The hardness difference of the 5 crane shafts is 1.8%, the difference in yield strength at 20℃ is 0.4%, the difference in tensile strength at 20℃ is 0.4%, the difference in elongation at 20℃ is 3.4%, and the difference in impact performance at 20℃ is 9.5%.

[0035] Comparative Example 1 The measured values ​​of the chemical composition mass percentages of the production method of the 1Cr17Ni2 crane shaft forging of Comparative Example 1 are: C: 0.19%, Mn: 0.54%, P: 0.03%, S: 0.005%, Si: 0.4%, Cr: 17%, Ni: 1.3%, and the balance is Fe and unavoidable impurities; The forging process of Comparative Example 1 is the same as that of Example 1.

[0036] The performance test results of the 1Cr17Ni2 crane shaft forging of Comparative Example 1 are as follows:

[0037] The hardness difference of the 5 crane shafts is 1.1%, the difference in yield strength at 20℃ is 0.6%, the difference in tensile strength at 20℃ is 0.6%, the difference in elongation at 20℃ is 9.1%, and the difference in impact performance at 20℃ is 10.4%.

[0038] The nickel content of Comparative Example 1 decreased. Compared with Example 1, other properties except hardness decreased significantly and products failed the flaw detection.

[0039] Example 2

[0040] Based on the forging steel of Example 1, the forging process of Example 2 is the same as that of Example 1, except that S8: Quenching: After the forgings are loaded into the furnace, the furnace temperature is raised to 800°C at a heating rate of 100°C / h. After being kept at this temperature for 4 hours, the furnace temperature is again raised to 1020°C at a heating rate of 100°C / h, kept at this temperature for 12 hours, and then water quenched; The performance test results of the 1Cr17Ni2 crane shaft forging of Example 2 are as follows:

[0041] The hardness difference of the 5 crane shafts is 5.3%, the difference in yield strength at 20℃ is 3.8%, the difference in tensile strength at 20℃ is 1.8%, the difference in elongation at 20℃ is 5.4%, and the difference in impact performance at 20℃ is 15.5%.

[0042] Example 2 is water quenching. Compared with Example 1, the hardness, 20°C yield strength, 20°C tensile strength and 20°C impact performance of the forgings of Example 2 are improved, and the 20°C elongation is reduced. In addition, the products that are accepted by the flaw detection are generally water quenching. It usually provides higher hardness and strength, but may lead to reduced plasticity and toughness. Although the hardness and strength of oil quenching are lower, it can provide better plasticity and toughness. At the same time, quenching and cooling too quickly usually lead to more residual stress, uneven martensitic transformation or quenching cracks inside the workpiece, and increase internal defects.

[0043] Example 3

[0044] Based on the forging steel of Example 1, the forging process of Example 3 is the same as that of Example 1, except that S1-S6 are repeated five times and there is no S7: S1: After the 14-inch billet weighing 1000kg is loaded into the furnace, the furnace temperature is increased to 300℃ at a heating rate of 80℃ / h and kept at this temperature for 0.8h; then, the furnace temperature is increased to 600℃ at a heating rate of 80℃ / h and kept at this temperature for 0.8h; then, the furnace temperature is increased to 1000℃ at a heating rate of 100℃ / h and kept at this temperature for 1.1h; finally, the furnace temperature is increased to 1180℃ at a heating rate of 100℃ / h and kept at this temperature for 1.7h; S2: Take out the blank, at which the surface temperature of the blank is 1140℃ and the core temperature is 1150℃; first perform two upsetting and one drawing operations, the 1430mm long blank is first upset to 750mm, then drawn to 1100mm, and finally upset to 650mm; The first upsetting forging ratio is 1.9; The first drawing forging ratio is 1.47; The second upsetting forging ratio is 1.69; S3: The forgings after the second upsetting are returned to the furnace, at which the surface temperature of the forgings is 920°C and the core temperature is 950°C; the return time is 2h and the return temperature is 1170°C; S4: Take out the forging and draw it to 1090 mm, with a drawing-to-forging ratio of 1.68; S5: Finish the forgings. The surface temperature of the finished forgings is 970°C and the core temperature is 990°C. S6: Place the forging in a 600°C trolley furnace for insulation for 1 hour. After the insulation is completed, the forging is furnace cooled until the surface and core of the forging reach room temperature. The cooling rate of the forging is measured to be 20°C / h. The duration of the five steps S1 to S6 in Example 3 is 260.5 hours.

[0045] The performance test results of the 1Cr17Ni2 crane shaft forging of Example 3 are as follows:

[0046] The hardness difference of the 5 crane shafts is 13.2%, the difference in yield strength at 20℃ is 6.1%, the difference in tensile strength at 20℃ is 4%, the difference in elongation at 20℃ is 26.3%, and the difference in impact performance at 20℃ is 14.8%.

[0047] The five crane shafts of Example 3 are forged individually, and their hardness, 20°C yield strength, 20°C tensile strength, 20°C elongation and 20°C impact performance are quite different from those of Example 1, and the production process is more time-consuming.

[0048] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for producing 1Cr17Ni2 crane shaft forgings, comprising the steps of pre-forging heating, forging, post-forging cooling, rough machining, heat treatment and finishing; characterized in that: The forging is made of 1Cr17Ni2 steel, and the element composition of the 1Cr17Ni2 steel is as follows by mass percentage: C: 0.12%~0.2%, Mn:≤1%, P:≤0.04%, S:≤0.03%, Si:≤1%, Cr:15%~18%, Ni:2.2%~3%, the balance is Fe and unavoidable impurities.

2. The method for producing 1Cr17Ni2 crane shaft forgings according to claim 1, characterized in that: The pre-forging heating step comprises: After the forging is loaded into the furnace at room temperature, it is heated to 290-310° C. and kept warm for 0.2-0.3 h / 100 mm according to the effective thickness of the forging; then it is heated to 590-610° C. and kept warm for 0.2-0.3 h / 100 mm according to the effective thickness of the forging; then it is heated to 990-1010° C. and kept warm for 0.3-0.4 h / 100 mm according to the effective thickness of the forging; finally it is heated to 1170-1190° C. and kept warm for 0.4-0.6 h / 100 mm according to the effective thickness of the forging.

3. The production method of 1Cr17Ni2 crane shaft forging according to claim 1, characterized in that: The pre-forging heating step consists of four step-wise heatings, wherein the heating rates of the first and second heatings of the forging are no more than 80°C / h, and the heating rates of the third and fourth heatings of the forging are no more than 100°C / h.

4. The method for producing 1Cr17Ni2 crane shaft forgings according to claim 3, characterized in that: The heating rates of the forging during the first and second heatings are lower than the heating rates of the forging during the third and fourth heatings.

5. The method for producing 1Cr17Ni2 crane shaft forgings according to claim 1, characterized in that: The initial forging temperature of the forging in the forging step is 1140-1150°C, and the final forging temperature of the forging in the forging step is not less than 900°C.

6. The method for producing 1Cr17Ni2 crane shaft forgings according to claim 1, characterized in that: The forging step includes two upsetting steps and two drawing steps which are performed alternately in sequence, wherein: The first upsetting forging ratio is 1.69~1.89; The first drawing forging ratio is 1.58~1.78; The second upsetting forging ratio is 1.35~1.46; The second drawing forging ratio is 4.85~5.

05.

7. The method for producing 1Cr17Ni2 crane shaft forgings according to claim 1, characterized in that: The post-forging cooling step comprises: After the forging step is completed, the forging is kept at a temperature within a range of 590-610° C. according to an effective thickness of 0.4-0.5 h / 100 mm of the forging, and then cooled to room temperature at a cooling rate of 20-30° C. / h.

8. The method for producing 1Cr17Ni2 crane shaft forgings according to claim 1, characterized in that: The heat treatment step includes sequential quenching and tempering steps; the quenching step is: The forging is heated to 790-810°C at a heating rate of no more than 100°C / h, and then kept warm for 1.3-1.4h / 100mm of the effective thickness of the forging; then the forging is heated to 1010-1030°C at a heating rate of no more than 100°C / h, and then kept warm for 3.9-4.0h / 100mm of the effective thickness of the forging, and finally oil quenched.

9. The method for producing 1Cr17Ni2 crane shaft forgings according to claim 8, characterized in that: The tempering step is: The cooled forging is heated to 650-670°C at a heating rate of no more than 100°C / h, kept warm for 5.9-6.0h / 100mm according to the effective thickness of the forging, and finally air-cooled.

10. The method for producing 1Cr17Ni2 crane shaft forgings according to claim 1, characterized in that: The forging is a composite forging, and the rough machining step divides the composite forging into a plurality of individual forgings.

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