Nitrogen-free low-temperature phosphating treatment method for chain pin shaft material

Abstract

The invention belongs to the technical field of metal surface pretreatment, and relates to a nitrogen-free low-temperature zinc phosphating treatment method for a chain pin shaft material. According to the method, a composite oxidation system composed of sodium percarbonate and tert-butyl peroxybenzoate is used for replacing a traditional nitrite accelerator at the temperature of 50-65 DEG C, online oxidation reduction potential (ORP) is used as a main control parameter, Fe < 2 + > concentration monitoring is combined, and a bath solution is maintained in a steady state interval of + 450 mV to + 520 mV and Fe < 2 + > 0.2-0.4 g / L. According to the process, energy consumption and nitrogen oxide emission (NOx) are remarkably reduced, sludge accumulation is avoided, fine grains of a film layer are compact, adhesive force is high, and film forming is uniform. Compared with traditional phosphorization, the method has the advantages that the energy consumption and NOx and sludge discharge are reduced, and the film forming stability of the complex part is improved.

Description

Technical Field

[0001] This invention belongs to the field of surface treatment technology for chain production raw materials, specifically relating to a nitrogen-free low-temperature phosphating treatment method for chain pin materials. Background Technology

[0002] Phosphating treatment of steel parts (represented by zinc-based / manganese-based acid phosphating) is widely used for corrosion protection, anti-galling, and pre-coating treatment of components such as chain sleeves, pins, and fasteners. In traditional production lines, NaNO2 is often used as an accelerating and oxidizing component, maintaining the Fe content in the bath... 2+ with Fe 3+ The dynamic balance is maintained to ensure rapid nucleation and growth of the membrane at high temperatures of 80-95 ℃. Process control mainly relies on pH, free acid / total acid (FA / TA), and timed manual replenishment of oxidant. This route is mature and reliable, but it has long been subject to three constraints: First, high energy consumption and cost (high-temperature constant heating, large heat loss); second, environmental and safety burdens, as NaNO2 decomposes under acidic conditions to release NOx (a general term for nitrogen oxides, including gaseous oxides such as nitric oxide and nitrogen dioxide), forming brown fumes and occupational exposure; large amounts of phosphorus- and iron-containing sludge, resulting in high pressure on solid waste and water treatment; third, insufficient process stability, as fluctuations in loading volume, geometrically complex internal cavities, and transient loads easily cause membrane weight and roughness drift, and manual feeding is difficult to respond to in a timely manner. Therefore, the industry is gradually seeking new low-temperature, nitrogen-free (nitrite-free) routes.

[0003] In China, there has been considerable exploration of nano-ceramic coatings (a composite of zirconium, titanium, and zirconium aluminum) as a green alternative for "phosphorus and nitrogen removal." Chinese patent CN103938198A discloses a phosphorus-free nano-ceramic agent (fluorozirconic acid, zirconium oxychloride, ammonium fluorozirconate, etc.), which can be treated at room temperature for short periods, produces almost no sediment, and significantly improves coating adhesion and corrosion resistance, emphasizing its friendliness to spray systems and waste reduction. The advantages of this technology are room temperature operation, low sludge production, and phosphorus-free operation, making it suitable for pretreatment before coating adhesion and environmentally friendly replacement. However, its mechanism belongs to ceramic conversion film, which differs significantly from phosphating films in terms of crystal phase, film weight, and tribological behavior. For mechanical parts subjected to wear or requiring subsequent saponification (such as chain pins), traditional phosphating films still have specific advantages in anti-galling, running-in wear, and grease retention; while ceramic films, although corrosion-resistant and with excellent adhesion, still have shortcomings in conditions such as controllable film weight, low-speed boundary lubrication, and fretting wear.

[0004] On the other hand, domestically produced water treatment and surface protection formulations featuring "phosphorus-free pre-filming and corrosion inhibition" have also emerged. For example, CN114086167A proposes a formulation using monosodium glutamate, a terpolymer, ammonium molybdate, and Zn. 2+The phosphorus-free pre-filming agent, primarily composed of organic and inorganic components, forms a protective layer on the equipment surface through a synergistic effect of organic and inorganic components, thereby reducing corrosion and extending service life. The advantages of this approach are that it avoids the introduction of orthophosphates and focuses on corrosion reduction and operation and maintenance; however, its application is mainly in conditions such as circulating cooling water and heat exchange equipment, with the goal of pre-filming for corrosion prevention rather than phosphating conversion films for friction pairs. For zinc-based acidic phosphating production lines, this type of "phosphorus-free pre-filming, corrosion inhibition" does not focus on the growth, weight, and grain refinement control of crystalline phosphating films under low-temperature conditions, making it difficult to directly transfer to production lines for phosphating mechanical parts.

[0005] In summary, existing technologies have several problems. First, there is a lack of nitrogen-free, low-temperature phosphating film-forming technologies suitable for mechanical wear scenarios. Second, there is a lack of a control system: it is difficult to suppress production fluctuations caused by the amount of workpiece and complex geometry, and the stability of film weight and roughness is insufficient. Third, there is no reliable path for limiting NOx and sludge emissions through the phosphating film route. Summary of the Invention

[0006] To solve the above technical problems, a dense, fine-grained phosphating film with equivalent or better performance than traditional high-temperature processes can be achieved at low temperatures without using nitrites, thereby significantly reducing energy consumption, NOx and sludge emissions and improving the film formation stability of complex components.

[0007] To achieve the above-mentioned technical objectives, the present invention provides the following technical solution.

[0008] In a first aspect, the present invention discloses a nitrogen-free low-temperature phosphating treatment method for chain pin materials, comprising the following steps: S1 Pretreatment: The workpiece is degreased, washed with water, pickled and activated in sequence; S2 tank preparation: Prepare zinc-based acidic phosphating solution with a pH value of 2.6–3.1; S3 Low-temperature film formation: Immerse the workpiece in the bath at 50-65°C for 3-8 minutes; S4 Online Control and Feeding: Using the oxidation-reduction potential (ORP) of the bath solution measured with an Ag / AgCl reference as the main control variable, the ORP is maintained within the range of +450 to +520 mV. A peroxide oxidation system containing sodium percarbonate (SPC) and / or tert-butyl peroxybenzoate (TBPB) is added to the bath solution. The feeding method is continuous feeding and / or intermittent quantitative feeding, with the start, pause, or feeding rate automatically adjusted based on online monitoring. When the ORP exceeds the upper limit of the range, 5–20 mg / L hydroxylamine sulfate is added to the bath solution for quenching. Simultaneously, Fe in the bath solution is reduced. 2+ The mass concentration was controlled at 0.2–0.4 g / L, and the pH value was controlled at 2.6–3.1; S5 Post-treatment: Two-stage water washing after exiting the tank, followed by saponification or oil sealing.

[0009] As a further improvement, the peroxide oxidation system is a combination of SPC and TBPB, wherein the mass concentration of SPC is 0.15-0.50 g / L and the mass concentration of TBPB is 0.02-0.10 g / L.

[0010] As a further improvement, the zinc-based acidic phosphating bath solution includes: H3PO4 12~18g / L, Zn 2+ 0.8~1.5g / L.

[0011] As a further improvement, the activation uses titanium-based and / or zirconium-based activators, the total metal concentration of the activation solution is 20-200 mg / L, and the interval between the completion of activation and the workpiece entering the tank does not exceed 10 minutes.

[0012] As a further improvement, to stabilize the primary crystals and suppress over-corrosion caused by over-oxidation, 5–30 mg / L of phosphonate complexing regulator and / or 5–20 mg / L of molybdate or tungstate are added to the bath as mild oxidation regulators.

[0013] As a further improvement, the start-up, pause, and feeding rate of the SPC continuous feeding and / or TBPB intermittent quantitative feeding are automatically adjusted based on whether the ORP is within a preset range of +450 to +520 mV, so as to maintain the ORP within the range.

[0014] As a further improvement, the Fe in the bath solution can be detected online or near-line. 2+ The mass concentration was maintained at 0.2–0.4 g / L; when Fe 2+ When the feed exceeds the set upper limit, increase the continuous feeding of SPC or briefly activate the intermittent quantitative feeding of TBPB, when Fe 2+ When the feed rate falls below the set lower limit, reduce the SPC feed rate and suspend the TBPB intermittent quantitative feed rate.

[0015] As a further improvement, the resulting zinc-based phosphating film has a film weight of 1.5–3.0 g / m³. 2 Surface roughness Ra≤1.2μm, and three standard deviations (3σ) of film weight fluctuation not greater than ±0.25 g / m 2 It also provides uniform coverage in complex areas of the chain pin material.

[0016] Secondly, the present invention also discloses a zinc-based nitrogen-free low-temperature phosphating bath composition, comprising: a) Main salt system: H3PO4 12~18g / L, Zn 2+ 0.8–1.5 g / L, preferably containing Ni 2+ 0.2~0.6g / L; b) Peroxide oxidation system: sodium percarbonate (SPC) and / or tert-butyl peroxybenzoate (TBPB), wherein the mass concentration of SPC is 0.15-0.50 g / L and the effective mass concentration of TBPB is 0.02-0.10 g / L; c) 5–30 mg / L phosphonate complexation modifiers and / or 5–20 mg / L molybdate or tungstate; Furthermore, the zinc-based nitrogen-free low-temperature phosphating bath composition does not contain accelerators with nitrite as the main component.

[0017] Thirdly, the present invention also discloses the use of the zinc-based nitrogen-free low-temperature phosphating bath composition described in the second aspect in the nitrogen-free low-temperature phosphating treatment of chain pin materials, obtaining a zinc-based phosphating film that meets the above-mentioned quality indicators at a low temperature of 50-65 ℃, and achieving a reduction of energy consumption of more than 30% and near-zero NOx emissions compared to the traditional 80-95 ℃ nitrite phosphating.

[0018] This invention utilizes sodium percarbonate (SPC) to provide a slow-release oxidation potential in the aqueous bulk phase and tert-butyl peroxybenzoate (TBPB) to provide rapid free radical oxidation at the interface. These two channels synergistically promote micro-dissolution-redeposition and primary crystal nucleation and fine grain growth on the steel surface under acidic (pH 2.6-3.1) and low-temperature (50-65℃) conditions. Automatic adjustment of continuous / intermittent feeding is achieved using ORP (+450~+520 mV) as the main control variable, and is combined with Fe... 2+ Steady-state (0.2-0.4 g / L) and hydroxylamine sulfate (HAS) undergo cross-limit quenching, forming a system that still possesses sufficient film-forming kinetics at low temperatures and can inhibit peroxidation and per-corrosion. Compared with existing technologies, the beneficial technical effects of this invention are: without using nitrite, it achieves a phosphating film equivalent to or better than traditional 90℃ phosphating (with stable film weight, low roughness, and good coverage), reducing overall energy consumption by approximately 30-40%, achieving near-zero NOx emissions, and reducing sludge volume by approximately 30%. It also significantly improves film formation stability in mass production for components with fluctuating loading volumes and complex internal cavities, providing more controllable phosphating quality and better environmental compliance for chain pin materials. Detailed Implementation

[0019] To better understand the technical solution of the present invention, the present invention will be described below in conjunction with specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the present invention. Equivalent variations made by those skilled in the art without departing from the spirit and scope of the claims fall within the protection scope of the present invention.

[0020] I. Process Flow and Equipment Composition The production line adopts a series system: degreasing—water washing—pickling—activation—low temperature phosphating—secondary water washing—oil sealing—drying.

[0021] The phosphating section is equipped with the following devices and sensors: 1) Phosphating tank: corrosion-resistant lining, circulating spray of tank solution, constant temperature control (50~65 ℃); 2) Online monitoring: An ORP electrode with Ag / AgCl reference was used for online monitoring of pH and conductivity; Fe... 2+ Near-line colorimetry is used; 3) Feeding system: continuous metering pump (for SPC), intermittent metering pump (for TBPB), over-limit quenching pump (for HAS); 4) Control unit: PLC, which implements ORP and Fe... 2+ Control and feeding start / stop logic.

[0022] II. Raw Materials and Formula Zinc-based main salt system: H3PO4 12~18 g / L, Zn 2+ 0.8~1.5 g / L; Ni optional 2+ 0.2–0.6 g / L for crystal form control; pH 2.6–3.1.

[0023] Peroxide oxidation system: Sodium percarbonate (SPC) 0.15~0.50 g / L (continuous feeding); tert-butyl peroxybenzoate (TBPB) effective concentration 0.02~0.10 g / L (intermittent feeding).

[0024] Activator: Titanium-based and / or zirconium-based activator, which may be selected from metatitanate, fluorozirconate, or their composite system; preferably a mixed activation solution containing 0.2-0.8 g / L sodium metatitanate and 0.05-0.20 g / L fluorozirconic acid. The activation solution is used at room temperature to 30 ℃ and pH 3.5-10, which can form highly active TiO2 / ZrO2 microcrystal nuclei on the metal surface to promote the fine crystal growth and uniform coverage of the phosphating film.

[0025] Regulators (optional): Phosphonate complexing regulators 5-30 mg / L; molybdates or tungstates 5-20 mg / L.

[0026] Over-limit quencher: hydroxylamine sulfate (HAS) 5–20 mg / L.

[0027] Prohibited ingredients: The bath solution does not contain accelerators whose main component is nitrite.

[0028] III. Process Steps A nitrogen-free low-temperature phosphating treatment method for chain pin materials includes the following steps: S1 Preprocessing Degreasing: Alkaline degreasing agent, 50-60 ℃, 2-5 min; wash with water.

[0029] Pickling: HCl 8-12% (volume fraction), 20-30 ℃, 1-3 min; wash with water.

[0030] Activation: Composite activator, total metal concentration 20-200 mg / L, room temperature or ≤30 ℃, 30-90 s; transfer to phosphating tank within 10 min after activation.

[0031] S2 slot Prepare the zinc phosphating bath solution according to the above concentration, and adjust the pH to 2.6-3.1; set the constant temperature to 55-60 ℃ (fine-tune according to the workpiece material and process cycle).

[0032] S3 low temperature film forming The workpiece is immersed in a phosphating bath and contacted at 50–65 °C for 3–8 min.

[0033] S4 Online Control and Feeding ORP measured with Ag / AgCl reference as the main control variable was maintained within the range of +450 to +520 mV; Fe 2+ pH value is used as an auxiliary control factor. The feeding strategy is as follows: SPC continuous feeding: typical target concentration 0.15~0.50 g / L, corresponding to automatic fine adjustment of the metering pump according to the intraday fluctuation of ORP (preferably ≤±10 mV); TBPB intermittent feeding: typical effective concentration 0.02~0.10 g / L, automatically starts briefly when the workpiece load on the production line increases or the ORP approaches the lower limit, and automatically stops after the load drops; HAS Limit Exceedance Quenching: When ORP exceeds the upper limit (520 mV), 5-20 mg / L hydroxylamine sulfate is automatically added, while TBPB is paused and SPC continuous flow is reduced until ORP returns to the set range. Fe 2+ Steady state: maintained at 0.2–0.4 g / L; when Fe 2+ If the SPC is above the upper limit, the system will automatically increase the SPC or temporarily open the TBPB; if it is below the lower limit, the SPC will be reduced or the TBPB will be suspended.

[0034] pH steady state: Maintain at 2.6-3.1. When pH < 2.6, add an appropriate amount of deionized water or alkaline neutralizing solution for fine adjustment; when pH > 3.1, add a small amount of main acid (H3PO4) for correction.

[0035] The above controls achieve stable oxidation driving force and resistance to transient fluctuations under low temperature conditions, avoiding coarse grains and over-corrosion induced by excessive oxygen.

[0036] S5 Post-processor After removal from the tank, perform two-stage water washing; apply light oil seal for 1–2 minutes; and dry at ≤120 ℃.

[0037] It should be noted that in step S2, a zinc-based acidic phosphating bath is selected, while another commonly used manganese-based acidic phosphating bath is discarded. This is because the chain pin material is medium carbon steel or alloy structural steel, and its workpiece temperature tolerance range is limited. The manganese-based phosphating system requires high temperatures and is prone to oxidation and instability, making it unsuitable for the low-temperature, nitrogen-free, peroxide oxidation system of this invention. In contrast, the zinc-based acidic phosphating bath can stably form a fine-grained phosphate film at 50–65 °C, exhibits good chemical compatibility with SPC and TBPB oxidation systems, and achieves excellent film formation results with uniform film weight and dense grains, while also having low energy consumption and low NOx emissions. Therefore, the selection of a zinc-based bath in this invention is based on a comprehensive choice considering process matching, performance optimization, and environmental balance.

[0038] ORP-Fe in step S4 2+ The dual-parameter control logic integrates electrochemical and colorimetric analysis principles to achieve real-time monitoring and adaptive adjustment of the bath solution state. Specifically, the ORP (oxidation-reduction potential) is detected by an online electrochemical electrode sensor, with the potential value calculated based on Ag / AgCl as the reference, reflecting the overall oxidation-reduction balance of the bath solution. The sampling period is 10–30 seconds, and the signal is used for ORP main parameter adjustment after filtering and hysteresis processing. Fe 2+ Concentration is detected using a near-line automatic colorimetric method, utilizing Fe 2+ The absorbance of the complex at 510 nm was quantitatively calculated, with a detection period of 30–60 min. The system uses ORP as the main control signal; when ORP is below +450 mV and Fe… 2+ When the concentration increases, the PLC automatically increases the SPC continuous flow rate and shortens the TBPB intermittent cycle; when the ORP is higher than +520mV and Fe 2+ When the concentration is below 0.2 g / L, the system suspends TBPB dosing, reduces the SPC flow rate, and may trigger hydroxylamine sulfate (HAS) quenching. If the two signals deviate (e.g., ORP is normal but Fe...), the system will suspend TBPB dosing, reduce the SPC flow rate, and may trigger hydroxylamine sulfate (HAS) quenching. 2+ If the value is abnormally high, then Fe will be executed first. 2+ The corrected route was achieved through dual-signal coordination, which dynamically maintained the oxidation driving force and metal ion balance in the bath. IV. Examples and Comparative Examples The examples selected two types of workpieces: chain pins and chain sleeves, both using the commonly used zinc-based main salt system; the comparative examples covered traditional NaNO2 high-temperature process, low-temperature single-path oxidation, and no OPR monitoring and control.

[0039] Example 1 (Chain pin material, zinc-based low temperature) Workpiece: 20CrMnTi pin material, round material, deburred.

[0040] Main salt: H3PO4 15 g / L; Zn 2+1.2 g / L; Ni 2+ 0.3 g / L; pH 2.8.

[0041] Peroxidation system: SPC 0.25 g / L (continuous); TBPB 0.05 g / L (intermittent).

[0042] Regulators: Phosphonate 15 mg / L; Molybdate 10 mg / L.

[0043] Process: T=55 ℃; film formation 6 min; ORP 470±15 mV; Fe 2+ =0.30 g / L.

[0044] Results (mean, sample size n=10): Membrane weight 2.38 g / m 2 (3σ=±0.22 g / m) 2 Ra = 1.10 μm; Salt spray ≥72 h; NOx <10 ppm; sludge volume reduced by approximately 32% compared to traditional methods.

[0045] Example 2 (Chain sleeve material, zinc-based low temperature) Sleeve material is also a commonly used material for chains. The commonly used raw material is flat wire. Example 2 is set up to verify whether the technical solution of the present invention is applicable to flat cross-section materials.

[0046] Workpiece: 20CrMnTi sleeve material, thin-walled deep hole part.

[0047] Main salt: H3PO4 14 g / L; Zn 2+ 1.0 g / L; Ni 2+ 0.2 g / L; pH 2.9.

[0048] Peroxidation system: SPC 0.20 g / L (continuous); TBPB 0.04 g / L (pulse).

[0049] Regulators: Phosphonate 10 mg / L; Tungstate 10 mg / L.

[0050] Process: T=56 ℃; film formation 5.5 min; ORP 468±12 mV; Fe 2+ =0.28 g / L.

[0051] Results (mean, sample size n=10): Membrane weight 2.05 g / m 2 (3σ=±0.20 g / m) 2 Ra = 1.08 μm; Salt spray ≥72 h; NOx <10 ppm.

[0052] Comparative Example A (Traditional NaNO2 high temperature, pin material) Main salt is the same as in Example 1; accelerator: NaNO2 8g / L; Process: Temperature 90 ℃; film formation 6 min; manual timed replenishment; no ORP monitoring.

[0053] Results (mean, sample size n=10): Membrane weight 2.20 g / m 2 (3σ=±0.35 g / m) 2 Ra = 1.60 μm; Salt spray for 48 hours; NOx 150–300 ppm; sludge volume approximately 1.47 times that of Example 1.

[0054] Comparative Example B (SPC only, low temperature, no TBPB, pin material) The main salt was the same as in Example 1; T = 55 °C; SPC was 0.30 g / L only, and the ORP target was the same as in Example 1. Results (mean, sample size n=10): Membrane weight 1.65 g / m 2 (3σ=±0.48 g / m) 2 Ra = 1.55 μm; Salt spray for 36 hours.

[0055] Comparative Example C (no ORP monitoring, low temperature SPC, TBPB, pin material) The formulation is the same as in Example 1; however, ORP monitoring is turned off, and SPC is manually added every 30 minutes, while TBPB is added at fixed intervals.

[0056] Results (mean, sample size n=10): Membrane weight 1.92 g / m 2 (3σ=±0.41 g / m) 2 (Ra=1.35μm, significant batch-to-batch variation); Salt spray for 48 hours.

[0057] V. Testing Methods Membrane weight (g / m 2 ): Chemical stripping weighing method; 3σ is used to represent three times the standard deviation range (±3σ), which is used to characterize process stability and product consistency.

[0058] Surface roughness Ra (μm): in accordance with GB / T 1031.

[0059] Salt spray (h): Performed in accordance with GB / T 10125.

[0060] NOx (ppm): Detected by electrochemical sensing.

[0061] Sludge quantity (kg / t tank liquid.month): weighed after settling and centrifugal drying.

[0062] Energy consumption (kWh / t steel): power of heating and circulating pumps in the phosphate section, converted to unit production capacity. VI. Test Results Test Result Comparison Summary Table

[0063] In summary, Examples 1 and 2 achieved 2.05–2.38 g / m³ at 55–56 °C. 2 The stable film weight and fine-grained surface with Ra≈1.1μm are superior to those of the conventional process Comparative Example A (90 ℃ / NaNO2). Comparative Example B shows that the low-temperature power is insufficient and the film weight and uniformity decrease significantly when only SPC is used, indicating that the rapid oxidation of the TBPB interface is crucial for complex internal cavities and primary crystal density. Comparative Example C shows that the film weight fluctuation increases and the probability of coarse crystals rises when there is no ORP monitoring, proving that ORP as the main control can suppress the fluctuations caused by process cycle and loading volume. Compared with the conventional process Comparative Example A, the low-temperature process adopted in this invention reduces energy consumption, NOx is close to zero, and sludge volume is reduced by about 28-32%, which meets the requirements of green manufacturing. The pin and sleeve are both chain motion pairs, and both ends are preferably zinc-based fine-grained and light film. This invention unifies the zinc-based system to cover both types of materials, simplifying the production line and stabilizing quality.

[0064] Those skilled in the art can make various equivalent substitutions or combinations of process parameters, feeding methods, monitoring methods, and equipment structures without departing from the spirit and essence of this invention. For example, TBPB in the oxidation system can be replaced by other organic peroxides, ORP detection can use different reference systems and be converted through algorithms, and Fe... 2+ Concentration can also be monitored in real time using online photometry or electrochemical methods. For all nitrite-free low-temperature zinc-based phosphating systems using the same or similar methods, the synergistic effect of peroxide composite oxidants and ORP-Fe... 2+ All technical solutions that achieve oxidation-reduction balance of the bath solution and obtain a fine-grained, dense phosphating film through dual closed-loop control should fall within the protection scope of this invention.

Claims

1. A process for nitrogen-free cryogenic phosphating of chain pin shaft material, characterized in that, The method comprises the following steps: S1 pretreatment: sequentially degreasing, washing, pickling and activating the workpiece; S2 tank preparation: preparing a zinc-based acidic phosphating tank solution, the pH value of which is 2.6-3.1; S3 low-temperature film forming: immersing the workpiece in the tank solution at 50-65 ℃ for 3-8 min; S4 online control and dosing: the redox potential (ORP) of the tank solution measured with reference to Ag / AgCl is the main control variable, the ORP is maintained in the range of +450~+520 mV, and a peroxygen oxidation system is added to the tank solution, the peroxygen oxidation system comprises sodium percarbonate (SPC) and / or tert-butyl peroxybenzoate (TBPB), the dosing mode is continuous dosing and / or intermittent quantitative dosing, and the opening, pause or dosing rate is automatically adjusted according to online monitoring; when the ORP exceeds the upper limit of the range, 5~20 mg / L of hydroxylamine sulfate is added to the tank solution for quenching; and at the same time, the mass concentration of Fe 2+ in the tank solution is controlled to be 0.2~0.4 g / L, and the pH value is controlled to be 2.6~3.1; S5 post-treatment: two-stage washing after leaving the tank, and saponification or oil sealing.

2. The method of claim 1, wherein, The peroxidation oxidation system is a combination of SPC and TBPB, wherein the mass concentration of SPC is 0.15-0.50 g / L, and the mass concentration of TBPB is 0.02-0.10 g / L.

3. The method of claim 1, wherein, The zinc-based acidic phosphating bath solution comprises: H3PO4 12-18 g / L, Zn 2+ 0.8-1.5 g / L.

4. The method of claim 1, wherein, The activation uses titanium-based and / or zirconium-based activators, the total metal concentration of the activation solution is 20-200 mg / L, and the interval time from the completion of activation to the workpiece entering the tank is not more than 10 min.

5. The method of claim 1, wherein, In order to stabilize the primary crystal and inhibit the over-corrosion caused by peroxidation, 5-30 mg / L phosphonate complexing regulator and / or 5-20 mg / L molybdate or tungstate are added to the tank solution as mild oxidation regulators.

6. The method of claim 1, wherein, The opening, suspension and feeding rate of the continuous feeding of SPC and / or the intermittent quantitative feeding of TBPB are automatically adjusted based on whether the ORP is in the preset range of +450 to +520 mV, so as to maintain the ORP in the range.

7. The method of claim 1, wherein, Fe 2+ The mass concentration is maintained at 0.2-0.4 g / L; when Fe 2+ The SPC continuous feeding is increased or the TBPB intermittent quantitative feeding is opened for a short time when Fe 2+ The SPC feeding is reduced and the TBPB intermittent quantitative feeding is suspended when Fe 8. The method of claim 1, wherein, The zinc-based phosphating film has a film weight of 1.5 to 3.0 g / m 2 , a surface roughness Ra of ≤ 1.2 μm, and a 3σ of the film weight fluctuation of not more than ± 0.25 g / m 2 .

9. A zinc-based, non-nitrogen, low temperature phosphating bath composition for use in the method of claim 1, characterized in that, The method comprises the following steps: a) main salt system: H3PO412-18 g / L, Zn 2+ 0.8-1.5 g / L, preferably containing Ni 2+ 0.2-0.6 g / L; b) peroxidation oxidation system: sodium percarbonate (SPC) and / or tert-butyl peroxybenzoate (TBPB), wherein the mass concentration of SPC is 0.15-0.50 g / L, and the effective mass concentration of TBPB is 0.02-0.10 g / L; c) 5-30 mg / L phosphonate complexing regulator and / or 5-20 mg / L molybdate or tungstate; and the composition does not contain an accelerator with nitrite as the main component.

10. Use of the process according to any one of claims 1 to 8 for the nitrogen-free low-temperature phosphating of chain pin shaft material, characterized in that A zinc-based phosphating film satisfying the quality index of claim 8 is obtained at 50-65 ℃.

Images