ENVIRONMENT-FRIENDLY WATER-BASED TREATMENT AGENT FOR IMPROVING PHOSPHATABILITY OF HIGH-STRENGTH STEEL

Abstract

The present invention belongs to the technical field of surface treatment for metal materials, and particularly relates to an environment-friendly water-based treatment agent for improving the phosphatability of high-strength steel. The water-based treatment agent is prepared by dissolving or dispersing a composition in an aqueous medium. The water-based treatment agent specifically consists of: A. a fluoride ion-containing compound; B. a compound selected from metal ion compounds containing Cu, Zn, Mn, Ni or Fe; C. a compound selected from organic acids; and D. a compound selected from surfactant. The water-based treatment agent can be diluted in water at a ratio of 1:0-20 for subsequent use. The treatment agent can enable the surface of a high-strength steel plate to have excellent phosphatability and is mainly applied to high-strength steel surface modification treatment.

Claims

1. An environmentally friendly water-based treatment agent for improving phosphatability of high-strength steel, wherein the water-based treatment agent is prepared by dissolving or dispersing a composition in an aqueous medium, wherein the water-based treatment agent specifically comprises: A. a compound selected from compounds containing fluoride ions; B. a metal ion compound selected from compounds containing Cu, Zn, Mn, Ni, and Fe; C. a compound selected from organic acids; D. a compound selected from surfactants.

2. The environmentally friendly water-based treatment agent for improving phosphatability of high-strength steel according to claim 1, wherein the compound containing fluoride ions is selected from one or more of ammonium fluorotitanate, ammonium fluorozirconate, potassium fluorotitanate, potassium fluorozirconate.

3. The environmentally friendly water-based treatment agent for improving phosphatability of high-strength steel according to claim 1, wherein a molar concentration of the F element in the water-based treatment agent solution is 0.3-1.8 mol/L, 0.3-1.7 mol/L, or 0.6-1.1 mol/L.

4. The environmentally friendly water-based treatment agent for improving phosphatability of high-strength steel according to claim 1, wherein the metal ion compound containing Cu is selected from sulfates, carbonates, and nitrates that contain copper ions; the metal ion compound containing Zn is selected from sulfates, phosphates, formates, and acetates that contain Zn ions; the metal ion compound containing Mn is selected from phosphates, carbonates, and nitrates that contain Mn ions; the metal ion compound containing Ni is selected from sulfates, nitrates, and carbonates that contain Ni ions; the metal ion compound containing Fe is selected from nitrates and oxalates that contain Fe ions.

5. The environmentally friendly water-based treatment agent for improving phosphatability of high-strength steel according to claim 1, wherein a molar concentration of the metal ion compound in the water-based treatment agent solution is 0.05-0.6 mol/L, 0.07-0.6 mol/L, or 0.1-0.25 mol/L.

6. The environmentally friendly water-based treatment agent for improving phosphatability of high-strength steel according to claim 1, wherein the organic acid compound is an organic acid compound with a complexing or chelating function, or is selected from one or more of citric acid, oxalic acid, tannic acid, lactic acid, tartaric acid, and salicylic acid.

7. The environmentally friendly water-based treatment agent for improving phosphatability of high-strength steel according to claim 1, wherein a molar concentration of the organic acid compound in the water-based treatment agent solution is 0.03-0.4 mol/L, or 0.05-0.2 mol/L.

8. The environmentally friendly water-based treatment agent for improving phosphatability of high-strength steel according to claim 1, wherein the compound selected from surfactants is selected from one or more of sodium dodecyl sulfate, sodium dodecyl sulfonate, calcium dodecyl sulfonate, octadecylamine and triethanolamine.

9. The environmentally friendly water-based treatment agent for improving phosphatability of high-strength steel according to claim 1, wherein a molar concentration of the surfactant in the water-based treatment agent solution is 0.002-0.015 mol/L, or 0.003-0.01 mol/L.

10. The environmentally friendly water-based treatment agent for improving phosphatability of high-strength steel according to claim 1, wherein the water-based treatment agent further comprises 0-20 parts by weight of water.

11. (canceled)

12. A method for improving phosphatability of high-strength steel, wherein the method comprises: treating the high-strength steel with the environmentally friendly water-based treatment agent according to claim 1 by immersion, spraying or roller coating.

13. The method according to claim 12, wherein the method further comprises: treating the high-strength steel with a degreasing agent to remove dirt and oil adhering to its surface, then washing it with pure water to remove alkaline matter remaining on the surface, and then using the environmentally friendly water-based treatment agent to perform surface treatment on the high-strength steel after blow drying.

14. A high-strength steel or a phosphated steel sheet obtained by phosphating the high-strength steel, wherein the high-strength steel has a nano-scale surface modification layer on the surface, wherein the nano-scale surface modification layer is formed from the environmentally friendly water-based treatment agent according to claim 1 after drying.

15. A method for phosphating high-strength steel, comprising: treating the surface of the high-strength steel using the method according to claim 12, and subjecting the high-strength steel obtained by treating the surface to degreasing, water washing, surface conditioning, phosphating, water washing and drying in sequence, so that the high-strength steel is phosphated.

16. The environmentally friendly water-based treatment agent for improving phosphatability of high-strength steel according to claim 4, wherein a molar concentration of the metal ion compound in the water-based treatment agent solution is 0.05-0.6 mol/L, 0.07-0.6 mol/L, or 0.1-0.25 mol/L.

17. The environmentally friendly water-based treatment agent for improving phosphatability of high-strength steel according to claim 6, wherein a molar concentration of the organic acid compound in the water-based treatment agent solution is 0.03-0.4 mol/L or 0.05-0.2 mol/L.

18. The environmentally friendly water-based treatment agent for improving phosphatability of high-strength steel according to claim 8, wherein a molar concentration of the surfactant in the water-based treatment agent solution is 0.002-0.015 mol/L or 0.003-0.01 mol/L.

19. The method for improving phosphatability of high-strength steel according to claim 12, wherein the high-strength steel is pickled high-strength steel or cold-rolled high-strength steel.

20. The high-strength steel or a phosphated steel sheet obtained by phosphating the high-strength steel according to claim 14, wherein the phosphated steel sheet has a phosphating crystal coverage rate of 80%; a phosphating crystal size of 6 m; and a phosphating film weight of 2 g/m.sup.2.

21. The high-strength steel or a phosphated steel sheet obtained by phosphating the high-strength steel according to claim 20, wherein the phosphated steel sheet has a phosphating crystal coverage rate of 100%.

Description

DETAILED DESCRIPTION

[0026] In order to provide better understanding of the present disclosure, the present disclosure is illustrated specifically by listing examples and comparative examples, but the scope of the present disclosure is not limited by these examples. The compositions of the surface treatment agents used and the type of the steel sheet to be treated are described as follows:

(1) Test Sample Sheet:

[0027] The material used in the examples was a typical 80 kg grade ultra-high strength steel with a specification of 1.2 mm and a composition as shown in Table 1.

TABLE-US-00001 TABLE 1 Composition information of the common cold-rolled steel sheet used in the examples Chemical composition % (mass percentage) C Mn Si Al Cr Mo Nb Ti 0.12 1.550 1.100 0.020 0.650 0.000 0.030 0.070

(2) Process for Processing and Cleaning the Sample Sheet:

[0028] The above material was processed into 30*70 mm sample pieces by shearing, spray-cleaned with an alkaline degreasing agent (pH=11-12) to remove din and oil adhering to the surface, then cleaned with pure water to remove residual alkaline matter on the surface, and dried with cold air for later use.

(3) Compositions of the Water-Based Surface Treatment Agents

[0029] The compositions and treatment methods of the environmentally friendly water-based surface treatment agents used in the examples are shown in Table 2. Comparative Example 4 means a material with a virgin surface that had not been surface treated with the treatment agent.

TABLE-US-00002 TABLE 2 Examples and compositions of the surface treatment agents used F-containing Organic acid compound (A) Metal salt (B) compound (C) Surfactant (D) F element content molar content molar content molar content Coating mol/L mol/L mol/L mol/L method Designation Type Content Type Content Type Content Type Content Method Ex. 1 Ammonium 1.7 Zn- 0.07 Citric 0.03 Triethanolamine 0.002 Immersion fluorotitanate containing acid phosphate Ex. 2 Potassium 1.7 Cu- 0.25 Oxalic 0.1 Sodium 0.015 Spraying fluorozirconate containing acid dodecyl sulfate sulfonate Ex. 3 Potassium 0.3 Fe- 0.6 Tartaric 0.4 Sodium 0.002 Immersion fluorotitanate containing acid dodecyl nitrate sulfate Ex. 4 Ammonium 0.9 Mn- 0.25 Oxalic 0.1 Calcium 0.009 Spraying fluorozirconate containing acid dodecyl phosphate sulfonate Ex. 5 Potassium 0.3 Ni- 0.07 Tannic 0.4 Octadecylamine 0.002 Roller fluorozirconate containing acid coating carbonate Ex. 6 Potassium 0.9 Zn- 0.6 Citric 0.03 Calcium 0.009 Roller fluorotitanate containing acid dodecyl coating phosphate sulfonate Comp. Potassium 0.02 Cu- 0.03 Tartaric 0.01 Calcium 0.001 Spraying Ex. 1 fluorozirconate containing acid dodecyl nitrate sulfonate Comp. Potassium 2 Mn- 0.7 Citric 0.1 Octadecylamine 0.015 Immersion Ex. 2 fluorotitanate containing acid phosphate Comp. Ammonium 0.9 Mqn- 0.25 Oxalic 0.1 Calcium 0.02 Spraying Ex. 3 fluorozirconate containing acid dodecyl phosphate sulfonate Comp. Ex. 4

[0030] The surface-treated sample pieces obtained in the above Examples and Comparative Examples were coated with anti-rust oil in an amount of 1000 mg/m.sup.2, allowed to stand for one week, and then subjected to pre-painting treatment for evaluation of phosphatability. Laboratory simulation was performed with reference to the pre-painting treatment process flow in an automobile factory, mainly including steps of degreasing, surface conditioning and phosphating. The relevant treatment agents selected were commercial products available from Parkerizing. The specific process parameters are shown in Table 3.

TABLE-US-00003 TABLE 3 Phosphating process parameters Water Surface Water Pure water Step Degreasing washing conditioning Phosphating washing washing Drying Treatment FC-L4460 PL-Z PB-L3065 agent Treatment Immersion Spraying Immersion Immersion Spraying Spraying Heat drying method Treatment 40 C. Room Room 35 C. Room Room 90 C. temperature temperature temperature temperature temperature Treatment 90 s 20 s 30 s 120 s 20 s 20 s time

[0031] After the sample pieces were treated in the above manner, the phosphating crystal coverage rate and crystal size were observed microscopically using a scanning electron microscope, and the phosphating film weight was measured using a chemical dissolution method. The specific methods are as follows:

(1) Evaluation of Phosphating Crystal Coverage Rate

[0032] The phosphated surfaces of the sample pieces were observed using a scanning electron microscope (equipment: Zeiss SEM SIGMA500) at a magnification of 1000 times, and the evaluation was done in terms of the fraction of the area covered by the phosphating film. [0033] : Phosphating film coverage rate=100% [0034] : 80%Phosphating film coverage rate<100% [0035] : 60%Phosphating film coverage rate<80% [0036] x: Phosphating film coverage rate<60%

(2) Determination of Phosphating Crystal Size

[0037] The phosphated surfaces of the sample pieces were observed using a scanning electron microscope (equipment: Zeiss SEM SIGMA500) at a magnification of 2000 times. The length dimensions of 5 random phosphating crystals were measured using the scale, and the average value was taken.

(3) Determination of Phosphating Film Weight

[0038] First, a 30*70 mm phosphated sample piece was weighed (Mettler MS-TS analytical balance) and recorded as W.sub.0. Then, the sample piece was immersed in a phosphating film stripping solution (solution: 50 g/L anhydrous chromic acid, temperature: 75 C.) for 15 min. After taking the sample piece out, it was rinsed with deionized water for 40 s, dried with cold air, and weighed for the second time to obtain a weight recorded as W.sub.1. The weight of the phosphating film W was obtained by calculation:

[00001]$W=\left(W_0-W_1\right)/S_{\mathrm{surface}\mathrm{area}\mathrm{of}\mathrm{sample}\mathrm{piece}}.$

[0039] As it can be seen from the implementation effect (as shown in Table 4), Examples 1-6 exhibited good phosphatability with regard to all of the various evaluation items, especially Examples 1, 2, 3, 4 and 6 which showed excellent overall performances. A comparison between the Examples and Comparative Example 4 shows that the phosphatability of each of the materials that were surface treated with the treatment agent was improved significantly. A comparison between Example 6 and Comparative Example 1 shows that when the contents of the components in the treatment agent were insufficient, it was unlikely to improve the phosphatability of the sample surface effectively by the treatment. As it can be seen from Examples 1, 2 and Comparative Example 2, the addition of appropriate amounts of the F-containing compound and metal salt could optimize the phosphatability of the sample surface, but excessive addition was not conducive to rapid growth of the phosphating film due to the increase in film thickness, resulting in a decrease in phosphatability. As it can be seen from Example 4 and Comparative Example 3, excessive addition of the surfactant affected the film-forming effect of the treatment agent, and thus notably reduced the effect of the treatment on the optimization of the phosphatability of the sample surface. As it can be seen from Examples 3, 4 and 5, the treatment agent was compatible with typical coating methods such as spraying, immersion and roller coating, and had a wider range of process adaptability.

TABLE-US-00004 TABLE 4 Performances of the examples Coverage rate Crystal size Film weight Designation (rating) (m) (g/m.sup.2) Ex. 1 3.2 2.5 Ex. 2 2.3 2.3 Ex. 3 3.6 2.5 Ex. 4 2.9 2.4 Ex. 5 5.7 2 Ex. 6 3.8 2.3 Comp. Ex. 1 8.1 1.9 Comp. Ex. 2 X 7.9 1.6 Comp. Ex. 3 8.5 1.8 Comp. Ex. 4 X 10.1 1.4

[0040] Of course, those skilled in the art should appreciate that the above examples are only used to illustrate the present disclosure, rather than to limit the present disclosure. Any changes or modifications to the above examples will fall within the scope of the claims in the present disclosure, so long as they are within the spirit of the present disclosure.