New technology of GCr15 cold-drawn material for railway bearing rolling body through zinc-series surface phosphating

Abstract

The invention discloses a novel zinc-series surface phosphating GCr15 cold-drawn material process for a railway bearing rolling body. The novel zinc-series surface phosphating process solves the problems that a traditional manganese-series phosphating solution is high in cost; the phosphating reaction temperature is high, and the production difficulty is high. According to the technical scheme of zinc system surface phosphating, before surface phosphating treatment, finished steel is subjected to polishing treatment, and the surface roughness is not larger than 2.0 micrometers; a zinc phosphating process is adopted, and a nitrate accelerant is added into a zinc phosphating solution in a matched mode; 8%-10% of a zinc phosphating agent and 90%-92% of water. The total acidity in the phosphating tank is 20-40 pt, the free acidity in the phosphating tank is 2-5 pt, and the accelerant in the phosphating tank is 2-5 pt; the temperature in the reaction process is controlled to be 60-70 DEG C; during phosphating, the whole bundle of steel is repeatedly moved up and down, and the steel is scattered when touching the bottom in a static state; and after phosphorization, immersing in hot water, and rapidly air-drying. The method has the advantages that the temperature in the phosphating process is obviously reduced, the production difficulty is reduced, the energy consumption and cost are reduced, and the environmental pollution is reduced; and the cutting processing performance is improved.

Description

Technical Field

[0001] The invention belongs to the field of metal material surface processing and relates to surface processing of high carbon chromium bearing steel cold-drawn material, mainly to surface phosphating treatment of GCr15 cold-drawn finished steel material for railway freight car bearing rolling elements, with specifications mainly ranging from Φ21mm to Φ25mm. Background Art

[0002] Domestic and foreign bearing manufacturers mostly use cold processing to process raw steel into bearing rolling elements; however, cold processing places higher quality requirements on steel, which not only requires uniform hardness and size, but also requires sufficient lubrication on the surface. The phosphating film generated on the surface of steel by phosphating treatment can play a role in friction reduction and lubrication, effectively avoiding defects such as flash and burrs that affect the subsequent processing quality of bearing rolling elements during cold processing. Therefore, the phosphating process has been widely used in metal cold processing. The surface phosphating process is a process in which a phosphate chemical conversion film is formed by chemical and electrochemical reactions. The phosphate conversion film formed is called a phosphating film. The main purpose of phosphating is to provide protection for the metal matrix and prevent the metal from being corroded to a certain extent; it plays a role in friction reduction and lubrication in the metal cold processing process. At present, the phosphating process in the railway freight car industry is manganese phosphating, but manganese phosphating has the problem of high cost of raw materials for phosphating liquid; the phosphating reaction temperature is high, usually reaching 80℃~90℃, which is difficult to produce, and the high phosphating reaction temperature is very likely to cause problems such as volatilization of the phosphating liquid. Summary of the invention

[0003] The invention discloses a new process for zinc-based surface phosphating of GCr15 cold-drawn material for railway bearing rolling elements, which solves the problems of high raw material cost of traditional manganese-based phosphating solution, high phosphating reaction temperature, great production difficulty, and high phosphating reaction temperature that easily causes volatilization of the phosphating solution.

[0004] In order to achieve the above object, the present invention adopts the following technical scheme:

[0005] 1. The process flow is electric furnace + LF refining + VD vacuum degassing + die casting electrode blank + electroslag remelting + blanking + rolling + spheroidizing annealing + drawing + polishing + surface phosphating treatment.

[0006] 2. Chemical composition is shown in Table 1.

[0007] Table 1

[0008]

[0009] 3. Use protective atmosphere electric slag furnace to produce electric slag ingots, the melting rate is set to 7.0kg / h, the current range is 7000A~15000A, the voltage range is 50V~70V, the ternary pre-melted slag system is selected, and the slag amount is 120kg;

[0010] 4. The rolling process adopts controlled rolling and controlled cooling technology, with a soaking temperature of 980℃~1040℃, a final rolling temperature of 850℃~950℃, and a red-returning temperature of 650℃~750℃ after water penetration.

[0011] 5. Use an electric continuous furnace for spheroidizing annealing, and implement a two-stage annealing process. The temperature of the first stage is 805℃~810℃, and the temperature of the second stage is 705℃~710℃.

[0012] 6. Billeting + rolling + spheroidizing annealing + drawing.

[0013] 7. Before surface phosphating treatment, the finished steel is polished and the surface roughness is not greater than 2.0um.

[0014] 8. Zinc phosphating process production flow: zinc surface phosphating treatment + hot water washing + air drying + applying anti-rust oil.

[0015] 9. Use zinc phosphating process, zinc phosphating solution and add nitrate accelerator; zinc phosphating solution is composed of phosphating agent: 8%~10%, water: 90%~92%. The total acidity in the phosphating tank is 20pt~40pt, the free acidity is 2pt~5pt, and the accelerator is 2pt~5pt.

[0016] 10. The accelerator should be added evenly and stirred thoroughly before the phosphating reaction, and then added in small amounts and frequently.

[0017] 11. The temperature of zinc phosphating reaction process is controlled at 60℃~70℃.

[0018] 12. During phosphating, move the entire bundle of steel up and down repeatedly, and when it is still, it will touch the bottom and spread out.

[0019] 13. After phosphating, immerse in hot water to clean the phosphating liquid on the surface of the finished steel.

[0020] 14. After cleaning with hot water, spread the steel out flat and allow the moisture on the surface to dry quickly.

[0021] 15. After the moisture on the steel is air-dried, immerse it in anti-rust oil to improve the anti-rust effect.

[0022] The invention points of the present invention:

[0023] The present invention adopts zinc-based surface phosphating treatment technology for the first time to apply to finished steel products to improve cutting performance; before the phosphating reaction, the steel product is surface polished, and the pickling process before phosphating can be eliminated.

[0024] The advantages of this invention over the traditional phosphating process are:

[0025] 1. Traditional finished steel surface phosphating treatment uses manganese-based phosphating solution. The zinc-based surface phosphating process can significantly reduce the phosphating process temperature from the traditional 80℃~90℃ to 60℃~70℃, reducing production difficulty, energy consumption, and environmental pollution.

[0026] 2. The surface polishing treatment before the phosphating reaction cancels the pickling process before phosphating. From a technical point of view, it can prevent the quality problems such as improper pickling operation affecting the phosphating effect and rust after phosphating; from the perspective of process cost, it can reduce the cost of the pickling process; from the perspective of production organization, it can shorten the phosphating process, improve production efficiency, and reduce production difficulty; from an environmental protection point of view, it can reduce environmental pollution and waste acid disposal caused by the pickling process. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a GCr15 cold-drawn finished steel for railway freight car bearing rolling elements that has undergone zinc-based surface phosphating treatment.

[0028] Figure 2 This is a schematic diagram of the state of the zinc surface phosphating film under a high-power electron microscope.

[0029] Figure 3 The rolling element material of railway freight car bearings is made from GCr15 finished steel that has undergone zinc-based surface phosphating treatment. DETAILED DESCRIPTION

[0030] The present invention is described in detail below by examples.

[0031] Examples 1-3 all use the following same process:

[0032] 1. The process flow includes electric furnace + LF refining + VD vacuum degassing + die casting electrode blank + electroslag remelting + blanking + rolling + spheroidizing annealing + drawing + polishing + surface phosphating treatment.

[0033] 2. Use protective atmosphere electric slag furnace to produce electric slag ingots, the melting rate is set to 7.0kg / h, the current range is 7000A~15000A, the voltage range is 50V~70V, and the ternary pre-melted slag system is selected, and the slag amount is 120kg;

[0034] 3. The rolling process adopts controlled rolling and controlled cooling technology, with a soaking temperature of 980℃~1040℃, a final rolling temperature of 850℃~950℃, and a red-returning temperature of 650℃~750℃ after water penetration.

[0035] 4. Use an electric continuous furnace for spheroidizing annealing, and implement a two-stage annealing process. The temperature of the first stage is 805℃~810℃, and the temperature of the second stage is 705℃~710℃.

[0036] 5. Billeting + rolling + spheroidizing annealing + drawing.

[0037] 6. Before surface phosphating treatment, the finished steel is polished and the surface roughness is not greater than 2.0um.

[0038] 7. Zinc phosphating process production flow: zinc surface phosphating treatment + hot water washing + air drying + applying anti-rust oil.

[0039] Example 1

[0040] ⑴ The proportion of zinc phosphating solution is phosphating agent: 8%, water: 92%; the total acidity in the phosphating tank is 25pt, the free acidity is 2.5pt, and the accelerator is 5pt.

[0041] ⑵The temperature of zinc phosphating process is controlled at 60℃.

[0042] ⑶ Move the steel in the phosphating solution up and down every 3 minutes.

[0043] ⑷ After phosphating, spread out and air dry for 10 minutes (such as Figure 1 shown).

[0044] Phosphating effect: Phosphating film coverage 97%, phosphating film thickness 13g / m 2 No rust occurred 3 months after phosphating, which met the requirements for surface phosphating treatment.

[0045] Example 2

[0046] ⑴ The proportion of zinc phosphating solution is phosphating agent: 9%, water: 91%; the total acidity in the phosphating tank is 30pt, the free acidity is 3pt, and the accelerator is 4pt.

[0047] ⑵The temperature of zinc phosphating process is controlled at 65℃.

[0048] ⑶ Move the steel in the phosphating solution up and down every 4 minutes.

[0049] ⑷ After phosphating, spread it out and air dry for 8 minutes.

[0050] Phosphating effect: Phosphate film coverage 99%, phosphate film thickness 15g / m 2 (like Figure 2 There was no rust three months after phosphating, which met the requirements for surface phosphating treatment.

[0051] Example 3

[0052] ⑴ The proportion of zinc phosphating solution is phosphating agent: 10%, water: 90%. The total acidity in the phosphating tank is 35pt, the free acidity is 4pt, and the accelerator is 3pt.

[0053] ⑵The temperature of zinc phosphating process is controlled at 70℃.

[0054] ⑶ Move the steel in the phosphating solution up and down every 5 minutes.

[0055] ⑷ After phosphating, spread it out and air dry for 6 minutes.

[0056] Phosphating effect: Phosphating film coverage 98%, phosphating film thickness 15g / m 2 , no rust appeared 3 months after phosphating (such as Figure 3 As shown), it meets the requirements for surface phosphating treatment.

Claims

1. Zinc-based surface phosphating is used for a new process of cold-drawn GCr15 material for railway bearing rolling elements. The cold-drawn material process is: electric furnace + LF refining + VD vacuum degassing + die-cast electrode blank + electroslag remelting + blanking + rolling + spheroidizing annealing + drawing + polishing + surface phosphating treatment, which is characterized by: Surface phosphating treatment process: ⑴Before phosphating treatment, the finished steel is polished and the surface roughness is not greater than 2.0um; (2) Zinc phosphating solution and nitrate accelerator; The proportion of zinc phosphating solution is phosphating agent: 8%~10%, water: 90%~92%. The total acidity in the phosphating tank is 20pt~40pt, the free acidity is 2pt~5pt, and the accelerator is 2pt~5pt; ⑶ The accelerator should be added evenly and fully stirred before the phosphating reaction, and then added in small amounts and frequently; (4) The temperature of the zinc phosphating reaction process is controlled at 60℃~70℃; ⑸ During phosphating, the whole bundle of steel is moved up and down repeatedly, and when it is still, it touches the bottom and spreads out; (6) After phosphating, immerse in hot water to clean the phosphating liquid on the surface of the finished steel; ⑺After washing with hot water, spread it out flat and let the moisture on the surface of the steel dry quickly; ⑻ After the moisture on the steel is air-dried, immerse it in anti-rust oil to improve the anti-rust effect.

2. According to claim 1, the new process of zinc-based surface phosphating for GCr15 cold-drawn material for railway bearing rolling elements is characterized in that: ⑴ The proportion of zinc phosphating solution is phosphating agent: 8%, water: 92%; the total acidity in the phosphating tank is 25pt, the free acidity is 2.5pt, and the accelerator is 5pt; ⑵The temperature of zinc phosphating process is controlled at 60℃; ⑶ Move the steel in the phosphating solution up and down every 3 minutes; ⑷ After phosphating, spread it out and air dry for 10 minutes; Phosphating effect: Phosphating film coverage 97%, phosphating film thickness 13g / m 2 , no rust occurred 3 months after phosphating.

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