A forging method for producing large-size bearing steel forging billets from square billets

Abstract

The present invention relates to a forging method for producing large-size bearing steel forgings from a square billet, and belongs to the technical field of square billet forging. The forging method comprises the following steps: (1) Heating: The continuous casting square billet is delivered by hot delivery, and the square billet is heated to 1250-1270°C and then kept warm for 13-17 hours; (2) Drawing: The square billet after the above heating and insulation is drawn, and the forging ratio is 2.2-2.4, and the pressing amount of each pass is 0.25-0.27 times the cross-sectional height of the previous forging billet. The present invention adopts a single-pass square billet compaction process to improve the internal quality of high-carbon chromium bearing steel products, so that the steel structure after forging is dense, thereby meeting the quality requirements of flaw detection and reducing rework and quality scrap.

Description

Technical Field

[0001] The invention belongs to the technical field of square billet forging, and in particular relates to a forging method for producing large-size bearing steel forging billets from square billets. Background Art

[0002] Forging is to use the plasticity of materials to produce plastic deformation with the help of external forces to obtain forgings of the desired shape, size and certain structural properties. Bearing steel is a type of steel used to manufacture balls, rollers and sleeves of rolling bearings. It can also be used to make precision measuring tools, such as dies, measuring tools, taps and precision parts of diesel engine oil pumps. In order to improve the yield rate and shorten the delivery production cycle, more and more bearing steel forgings are currently produced by continuous casting round billets. However, due to direct drawing without upsetting, the internal deformation of the continuous casting billet is insufficient, the center is loose and the welding is not good, resulting in the problem of excessive flaw detection of the final product.

[0003] At present, the high carbon chromium bearing steel forgings with a diameter of 380-400mm are all produced by steel ingots. The quality of steel ingots is relatively poor due to the risers, and they need to be cut off after the finished products. Therefore, the yield rate is low, generally around 80%. The high carbon chromium bearing steel forgings with a diameter of 380-400mm are in accordance with the requirements of JB-T5000.8-2007 "General Technical Conditions for Heavy Machinery" Part 8 Forgings: When forging with steel ingots, if they are not upset, their forging ratio is generally not less than 3. The forging ratio of general forging products in the forging industry is actually above 4, so as to ensure that the product flaw detection level can meet the use requirements.

[0004] The high carbon chromium bearing steel forging blank with a diameter of 380-400mm is produced by using steel ingots, and the forging times are generally 3-4 times. This method not only increases the production cost and affects the production efficiency of the product, but also causes waste of raw materials.

[0005] Therefore, due to the relatively high C content in high-carbon bearing steel, continuous casting billets are prone to porosity defects, and the central porosity is more serious than that of general alloy steels. Effective measures need to be taken in forging to solve the porosity and shrinkage problems under low forging ratio and low cost conditions. Summary of the invention

[0006] The present invention provides a forging method for producing large-size bearing steel forgings from billets. The forging method provided by the present invention determines a suitable billet opening process in combination with the characteristics of the steel type without adding an upsetting process, adopts a one-time billet compaction process to improve the internal quality of high-carbon chromium bearing steel products, reduces the looseness of the billet center, and thus improves the internal quality of the forging billet, making the steel after forging dense, thereby meeting the quality requirements of flaw detection, reducing rework and quality waste, and significantly improving production efficiency.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solution: a forging method for producing large-size high-carbon chromium bearing steel forging billets from square billets, the forging method comprising the following steps:

[0008] (1) Heating: The continuous casting billet is delivered hot. The billet is heated to 1250-1270℃ and then kept warm for 13-17h.

[0009] (2) Drawing: The billet after heating and heat preservation is drawn, with a forging ratio of 2.2 to 2.4 and a reduction in each pass of 0.25 to 0.27 times the cross-sectional height of the billet in the previous pass.

[0010] In the heating of step (1) of the present invention, the continuous casting billet has a specification of 430-460 mm*610-650 mm.

[0011] In the heating step (1) of the present invention, after the billet is hot-delivered, the hot-delivery temperature is ≥550°C and the heating rate is ≤50°C / h.

[0012] In the step (2) of the present invention, the forging and drawing process is performed four times, and the steel sheet is turned 90 degrees after each drawing process.

[0013] The chemical composition and mass percentage of the high carbon chromium bearing steel forging blank described in the present invention are as follows: C: 0.95%-1.05%, Si: 0.15%-0.35%, Mn: 0.25%-0.45%, Cr: 1.40%-1.65%, Mo≤0.1%, P≤0.020%, S≤0.020%, O≤0.0012%.

[0014] The diameter φ of the high carbon chromium bearing steel forging blank described in the present invention is 380-400 mm.

[0015] The flaw detection level of the high carbon chromium bearing steel forging billet of the present invention reaches SEP1921 E / e level, and the specific standards are: the diameter of the equivalent flat bottom hole of a single point discontinuity is ≤3mm, and the diameter of the equivalent flat bottom hole of a long strip or dense point discontinuity is ≤2mm.

[0016] The high carbon chromium bearing steel forging blank of the present invention generally has a porosity of ≤0.5, a central porosity of ≤0.5, a banded structure of ≤3.0, and no microscopic pores.

[0017] The carbide liquid precipitation of the high carbon chromium bearing steel forging blank described in the present invention is 0.5.

[0018] The invention adopts an improved high-temperature diffusion process of steel ingots before forging, increases the heating temperature of the steel ingots, designs an optimal heating process, adjusts the holding time, designs a reasonable pressing process, and adopts a 4-pass compaction process, so that the specifications of the bearing steel square billets forgings can reach 380mm-400mm, the flaw detection level can reach SEP1921 E / e level, and qualified products can be produced at the lowest cost.

[0019] The beneficial effects of adopting the above technical solution are: 1. The high carbon chromium bearing steel forgings produced by the present invention can produce qualified high carbon chromium bearing steel forgings under small forging ratios by reasonably designing the heating and heat preservation and forging large reduction processes, and the problems of looseness in the center of the casting and uneven carbides are effectively solved. 2. The forging method provided by the present invention determines a suitable blanking process without adding an upsetting process, and adopts a one-time square drawing process to improve the internal quality of high carbon chromium bearing steel products, reduce the looseness in the center of the blank, and thus improve the internal quality of the forging blank, so that the steel structure after forging is dense, thereby meeting the quality requirements of flaw detection, and the flaw detection of products with specifications of Φ380-400mm reaches the optimal level, reducing rework and quality scrap, and significantly improving production efficiency. DETAILED DESCRIPTION

[0020] The present invention will be further described in detail below in conjunction with specific embodiments.

[0021] Example 1

[0022] A forging method for producing large-size high-carbon chromium bearing steel forging blanks from square billets, the forging method of the forging blank adopts the following specific processes:

[0023] (1) Heating: The forging product is made of GCr15, the cross-sectional specification of the billet is 460mm*610mm, the continuous casting billet is delivered by hot delivery, the hot delivery temperature is 580℃, the heating rate is 40℃ / h, and the billet is heated to 1250℃ and then kept warm for 14h;

[0024] (2) Drawing: The billet after heating and heat preservation is drawn by a direct drawing forging process with a forging ratio of 2.4. A 350 mm flat anvil is used for drawing. The fillet radius of the wide flat anvil is 35 mm and the length is 1300 mm.

[0025] The forging and drawing passes are 4 times. After each drawing pass, the forging blank is turned 90° and then drawn for the next pass. The reduction in each pass is 0.25 times the cross-sectional height of the forging blank in the previous pass. After 4 drawing passes, the forging blank is rounded and finished into a forging blank product with a diameter of 380mm.

[0026] The chemical composition and percentage of the high carbon chromium bearing steel forging blank obtained in this embodiment are shown in Table 1, and the specifications and properties are shown in Table 2. Ultrasonic flaw detection meets the SEP 1921 E / e grade requirements.

[0027] Example 2

[0028] A forging method for producing large-size high-carbon chromium bearing steel forging blanks from square billets, the forging method of the forging blank adopts the following specific processes:

[0029] (1) Heating: The forging product is made of GCr15, the cross-sectional specification of the billet is 430mm*650mm, the continuous casting billet is delivered by hot delivery, the hot delivery temperature is 560℃, the heating rate is 50℃ / h, and the billet is heated to 1260℃ and then kept warm for 15h;

[0030] (2) Drawing: The billet after heating and heat preservation is drawn by a direct drawing forging process with a forging ratio of 2.3. A 350 mm flat anvil is used for drawing. The fillet radius of the wide flat anvil is 35 mm and the length is 1300 mm.

[0031] The forging and drawing passes are 4 times. After each drawing pass, the forging blank is turned 90° and then drawn for the next pass. The reduction in each pass is 0.27 times the cross-sectional height of the forging blank in the previous pass. After 4 drawing passes, the forging blank is rounded and finished into a forging blank product with a diameter of 390mm.

[0032] The chemical composition and percentage of the high carbon chromium bearing steel forging blank obtained in this embodiment are shown in Table 1, and the specifications and properties are shown in Table 2. Ultrasonic flaw detection meets the SEP 1921 E / e grade requirements.

[0033] Example 3

[0034] A forging method for producing large-size high-carbon chromium bearing steel forging blanks from square billets, the forging method of the forging blank adopts the following specific processes:

[0035] (1) Heating: The forging product is made of GCr15, the cross-sectional specification of the billet is 440mm*630mm, the continuous casting billet is delivered by hot delivery, the hot delivery temperature is 580℃, the heating rate is 30℃ / h, the billet is heated to 1270℃ and then kept warm for 17h;

[0036] (2) Drawing: The billet after heating and heat preservation is drawn by a direct drawing forging process with a forging ratio of 2.2. A 350 mm flat anvil is used for drawing. The fillet radius of the wide flat anvil is 35 mm and the length is 1300 mm.

[0037] The forging and drawing passes are 4 times. After each drawing pass, the forging blank is turned 90° and then drawn for the next pass. The reduction in each pass is 0.26 times the cross-sectional height of the forging blank in the previous pass. After 4 drawing passes, the forging blank is rounded and finished into a forging blank product with a diameter of 400mm.

[0038] The chemical composition and percentage of the high carbon chromium bearing steel forging blank obtained in this embodiment are shown in Table 1, and the specifications and properties are shown in Table 2. Ultrasonic flaw detection meets the SEP 1921 E / e grade requirements.

[0039] Example 4

[0040] A forging method for producing large-size high-carbon chromium bearing steel forging blanks from square billets, the forging method of the forging blank adopts the following specific processes:

[0041] (1) Heating: The forging product is made of GCr15, the cross-sectional specification of the billet is 460mm*610mm, the continuous casting billet is delivered by hot delivery, the hot delivery temperature is 550℃, the heating rate is 50℃ / h, the billet is heated to 1255℃ and then kept warm for 13h;

[0042] (2) Drawing: The billet after heating and heat preservation is drawn by a direct drawing forging process with a forging ratio of 2.2. A 350 mm flat anvil is used for drawing. The fillet radius of the wide flat anvil is 35 mm and the length is 1300 mm.

[0043] The forging and drawing passes are 4 times. After each drawing pass, the billet is flipped 90° and then drawn for the next pass. The reduction in each pass is 0.27 times the cross-sectional height of the previous forging billet. After 4 drawing passes, the billet is rounded and finished into a forging billet product with a diameter of 385mm.

[0044] The chemical composition and percentage of the high carbon chromium bearing steel forging blank obtained in this embodiment are shown in Table 1, and the specifications and properties are shown in Table 2. Ultrasonic flaw detection meets the SEP 1921 E / e grade requirements.

[0045] Example 5

[0046] A forging method for producing large-size high-carbon chromium bearing steel forging blanks from square billets, the forging method of the forging blank adopts the following specific processes:

[0047] (1) Heating: The forging product is made of GCr15, the cross-sectional specification of the billet is 460mm*610mm, the continuous casting billet is delivered by hot delivery, the hot delivery temperature is 585℃, the heating rate is 45℃ / h, and the billet is heated to 1268℃ and then kept warm for 16h;

[0048] (2) Drawing: The billet after heating and heat preservation is drawn by a direct drawing forging process with a forging ratio of 2.3. A 350 mm flat anvil is used for drawing. The fillet radius of the wide flat anvil is 35 mm and the length is 1300 mm.

[0049] The forging and drawing passes are 4 times. After each drawing pass, the billet is flipped 90° and then drawn for the next pass. The reduction in each pass is 0.26 times the cross-sectional height of the previous forging billet. After 4 drawing passes, the billet is rounded and finished into a forging billet product with a diameter of 395mm.

[0050] The chemical composition and percentage of the high carbon chromium bearing steel forging blank obtained in this embodiment are shown in Table 1, and the specifications and properties are shown in Table 2. Ultrasonic flaw detection meets the SEP 1921 E / e grade requirements.

[0051] Example 6

[0052] A forging method for producing large-size high-carbon chromium bearing steel forging blanks from square billets, the forging method of the forging blank adopts the following specific processes:

[0053] (1) Heating: The forging product is made of GCr15, the cross-sectional specification of the billet is 460mm*610mm, the continuous casting billet is delivered by hot delivery, the hot delivery temperature is 590℃, the heating rate is 35℃ / h, the billet is heated to 1265℃ and then kept warm for 15.5h;

[0054] (2) Drawing: The billet after heating and heat preservation is drawn by a direct drawing forging process with a forging ratio of 2.2. A 350 mm flat anvil is used for drawing. The fillet radius of the wide flat anvil is 35 mm and the length is 1300 mm.

[0055] The forging and drawing passes are 4 times. After each drawing pass, the forging blank is turned 90° and then drawn for the next pass. The reduction in each pass is 0.25 times the cross-sectional height of the forging blank in the previous pass. After 4 drawing passes, the forging blank is rounded and finished into a forging blank product with a diameter of 380mm.

[0056] The chemical composition and percentage of the high carbon chromium bearing steel forging blank obtained in this embodiment are shown in Table 1, and the specifications and properties are shown in Table 2. Ultrasonic flaw detection meets the SEP 1921 E / e grade requirements.

[0057] Table 1 Chemical composition and percentage of high carbon chromium bearing steel forgings of Examples 1-6 (%)

[0058]

[0059] Table 2 Specifications and properties of high carbon chromium bearing steel forgings of Examples 1-6

[0060]

[0061] By comparison, it can be seen that the high carbon chromium bearing steel forging blanks produced by the one-time drawing forging method in Examples 1-6 have an optimal flaw detection level for products with specifications of Φ380-400mm. It can be seen from the above examples that the forging method provided by the present invention determines a suitable blanking process without adding an upsetting process, and uses a one-time drawing process to improve the internal quality of high carbon chromium bearing steel products, reduce the looseness of the center of the blank, and thus improve the internal quality of the forging blank, so that the steel structure after forging is dense, thereby meeting the flaw detection quality requirements, reducing rework and quality scrap, and significantly improving production efficiency.

[0062] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A forging method for producing large-size high-carbon chromium bearing steel forging billets from square billets, characterized in that: The forging method comprises the following steps: (1) Heating: The continuous casting billet is delivered hot. The billet is heated to 1250-1270℃ and then kept warm for 13-17h. (2) Drawing: The billet after heating and heat preservation is drawn, with a forging ratio of 2.2 to 2.4, and the reduction in each pass is 0.25 to 0.27 times the cross-sectional height of the previous forging pass; In the heating of step (1), the continuous casting billet has a billet specification of 430-460 mm*610-650 mm; The high carbon chromium bearing steel forging blank generally has a porosity of ≤0.5 level, a central porosity of ≤0.5 level, a banded structure of ≤3.0 level, and no microscopic pores.

2. The forging method for producing large-size high-carbon chromium bearing steel forging blanks from square billets according to claim 1 is characterized in that: In the heating step (1), after the billet is hot-delivered, the hot-delivery temperature is ≥550°C, and the heating rate is ≤50°C / h.

3. The forging method for producing large-size high-carbon chromium bearing steel forging blanks from square billets according to claim 1 is characterized in that: In the step (2) of drawing, the forging drawing process is performed four times, and the steel sheet is turned 90 degrees after each drawing process.

4. The forging method for producing large-size high-carbon chromium bearing steel forging blanks from square billets according to claim 1, characterized in that: The chemical composition and mass percentage of the high carbon chromium bearing steel forging blank are as follows: C: 0.95%-1.05%, Si: 0.15%-0.35%, Mn: 0.25%-0.45%, Cr: 1.40%-1.65%, Mo≤0.1%, P≤0.020%, S≤0.020%, O≤0.0012%.

5. The forging method for producing large-size high-carbon chromium bearing steel forging blanks from a square billet according to any one of claims 1 to 4, characterized in that: The diameter φ of the high carbon chromium bearing steel forging billet is 380-400 mm.

6. The forging method for producing large-size high-carbon chromium bearing steel forging blanks from a square billet according to any one of claims 1 to 4, characterized in that: The flaw detection level of the high carbon chromium bearing steel forging billet reaches SEP1921 E / e level.

7. The forging method for producing large-size high-carbon chromium bearing steel forging blanks from a square billet according to any one of claims 1 to 4, characterized in that: The carbide liquid separation of the high carbon chromium bearing steel forging blank is ≤0.5 level.

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