FI96327C - Use of ferritic-perlite steel - Google Patents

Description

96327

Use of ferritic-perlite steel

The invention relates to the use of precipitation-reinforced ferritic perlite steels (AFP steels) as a material for gas valves in internal combustion engines.

In internal combustion engines, gas valves are intake and exhaust valves that regulate the gas exchange in the engine and seal the cylinder chamber.

The development of engines in the direction of ever-increasing powers 10 results in an ever-increasing thermal stress on the valves, exhaust valves around which hot flue gases flow, reaching operating temperatures of up to about 850 ° C. In contrast, gaseous fuel cools intake valves and rarely reaches temperatures above 15,550 ° C.

Valve materials require not only high heat resistance properties, but also certain operating properties. The following are the characteristics required of a friction hose double metal exhaust valve shown in Figure 1: A = high wear resistance at the head end and at the beginning; B = high strength and toughness under dynamic compressive, tensile bending stress; C = arm (e.g. steel 1.4718); 25 D = good sliding properties in the valve controller; E = friction weld; F = valve plate (eg steel 1.4871); G = high heat resistance up to approx. 800 ° C even under dynamic stress. Resistance to heat shocks. Resistant to corrosion caused by 30 hot exhaust gases; H = high wear resistance; I = coating with hard material (hard alloying).

Special valve materials have been developed for these properties, which are standardized in DIN 35 17480. Three groups of materials can be distinguished: 2 96327 - martensitic carbide steels, such as materials Nos. 1.4718, 1.4731 and 1.4748, - austenitic carbide steels, some of which are precipitation-reinforcing, such as materials Nos. 1.4873, 5 1.4875, 1.4882, 1.4785 and - austenitic, precipitation-reinforcing mixtures, such as materials Nos. 2.4955, 2.4952.

When designing valves subject to different loads, valve manufacturers take into account the different properties of the valve materials. For example, lightly loaded suction valves are often made in the form of single metal valves ("single valves") in steel 14718 (X 45 CrSi 9 3).

For example, the hardened and tempered base bars are partially heated and hot formed into a pear shape. The valve plate formed by the hammer mill, followed by hardening and discharge or simply annealing, is then finished. In the case of heavily stressed exhaust valves, valve manufacturers are often forced to properly fit the valve materials together. As shown in Fig. 1, for example, in the case of a bimetallic valve, the high heat resistance and corrosion resistance of precipitation-reinforced austenitic steel can be combined with the high wear resistance and good sliding properties of hardened martensitic steel by friction welding of steel 9.48 3).

In the state of the art, more than half of the total valve material requirements for suction valves and 30 lightly stressed exhaust valves, as well as suction and exhaust metal valves, are met by steel 1.4718 (X 45 CrSi 9 3) or modifications thereof. These steels are processed by steelmakers and valve manufacturers according to the main manufacturing procedures shown in Figures 2 and 3.

It is an object of the present invention to replace previously used martensitic carbide steels, which both the steelmaker and the valve manufacturer have to subject to several heat treatments according to the manufacturing process, with blades 5 which achieve the required valve properties as far as possible without heat treatment and which are cheaper to machine.

In order to solve this problem, it is proposed in the present invention to use precipitation-reinforcing ferritic-perlite steels whose composition is set out in the appended claims.

It was found that both the wire after rolling and also after stamping or forging, when cooled from a high rolling temperature in air ("BY mode"), the AFP blade-15 has mechanical-technological values comparable to those of 1.4718 steel. Table 1 shows the chemical composition, while Table 2 and Figure 4 show the strength properties at room temperature and elevated temperatures. Table 3 and Figure 5 show the creep fracture toughness of the reference materials 1.4718 (X 45 CrSi 9 3) and AFP steel and show that in the BY state, AFP steels are a reasonable alternative to the prior art 1.4718.

After annealing and molding, suction valves made of AFP steel by the valve manufacturer in accordance with the present invention were air-cooled and tested in engines without further heat treatment. The test results were positive.

The steels of this invention have the advantage over previously used materials in gas valves that they can be easily produced economically by the procedures shown in Figures 6 and 7.

Comparing these procedures with the prior art's main manufacturing processes shown in Figures 2 and 3, it can be seen that AFP steels do not require heat treatments in contrast to known valve steels.

Another advantage, due to the lower susceptibility of AFP steels to cracking and carbon loss compared to the known valve steel 1.4718 and also due to the absence of carbon loss due to the lack of heat treatments, is that the 100% high-gloss grinding of the semi-finished product by 1.4718 requires additional rolling, can be replaced by partial grinding in the case of AFP-te-10 steel. In addition, the amount of machining in centrifugal grinding of tan steel can be reduced or even eliminated if the ground bars are replaced by drawn bars in the manufacture of gas valves from AFP steels.

15 In addition to the lower susceptibility to cracking and carbon loss, AFP steels have the following other advantages over martensitic carbide valve steels: - lower alloying costs 20 - improved continuous castability - lower sensitivity to coarse-grained recrystallization - improved chipping properties

Taken together, these advantages mean that the use of AFP-25 steels for gas valves in internal combustion engines represents significant cost savings for both steelmakers and valve manufacturers.

5 96327

Table 1: Reference steels: 1.4718 (X 45 CrSi 9 3) and AFP steel, chemical composition - melt analyzes (values in weight percent): 5 steel 1.4718 AFP steel _A_ B_ C 0.44 0.43

Si 2.78 0.66

Mn 0.32 1.38 10 P 0.015 0.008 S 0.003 0.027

Cr 8.93 0.15

Mo 0.12 0.02

Ni 0.20 0.08 15 V 0.03 0.12 W 0.02 <0.01 Al 0.027 0.047 B <0.0004

Co 0.06 0.008 20 Cu 0.04 0.10 N 0.018 0.016

Nb <0.005 <0.005

Ti <0.003 <0.003

Sn <0.003 0.012 25 As 0.008 0.010 6 96327

Table 2: Reference steels: 1.4718 (X 45 CrSi 9 3) and AFP steel. Strength properties at room temperature and elevated temperatures. A = 5 1.4718, diameter 17.5 mm; standard hardening and rejuvenation; B = AFP steel, diameter 9.32 mm; BY / pulled / polished.

Steel Test heat- Rp0 2 Rpl 0 Rn Rp0.2 A5 Z

pötila N / mm2 N / mm2 N / mm2 rJ%% 10 ------------------------------------ -------------------- 20 899 959 1098 0.93 18.0 53.5 A 450 611 708 776 0.78 26.8 76.0 1.4718 500 472 584 638 0.74 34.0 84.0 550 344 440 510 0.67 38.3 90.1 15 20 876 - 1069 0.82 14.5 54.0 450 564 651 681 0.83 1) 72.0 B 500 433 529 536 0.81 1) 70.0 AFP - 550 337 399 400 0.84 1) 70.0 20 steel 1) Fracture outside the measuring sign zone teaspoon 7 96327

Table 3: Reference steels: 1.4718 (X 45 CrSi 9 3) and AFP steel. Creep fracture toughness at 450, 500 and 550 ° C with a stress time of 102 and 103 hours.

5 A = 1.4718 diameter 17.5 mm; standard hardening and emission; B = AFP steel; BY / drawn / ground D = steel diameter 9.32 mm 10 450 500 380 A 500 330 230 1.4718 550 210 130 450 410 310 15 B 500 260 150 AFP steel 550 140 70

Claims (3)

1. Use of precipitable curable style consisting of 5 0.20 - 0.60% koi 0.20 - 0.95% silica 0.50 - 1.80% manganese 0.004 - 0.04% nitrogen 0.05-0 , 20% vanadium and or niobium 10 and optionally individually or together not more than 0.20% sulfur not more than 0.70% chromium not more than 0.10% aluminum 15 not more than 0.05% titanium residual iron and to the melt associated impurities, as gas valve manufacturing material for internal combustion engines. Use of style according to claim 1, with 0.35 - 0.50% koi 0.40 - 0.80% silicon 1.00 - 1.60% manganese 0.05 - 0.50% chromium 0.01 - 0.05% aluminum 0.008 - 0.03% nitrogen 0.05 - 0.12% vanadium and the residual iron and melting associated impurities for the end mill according to claim 1. Use of style according to claim 1, which style additionally contains individually or together not more than 0.05% sulfur, not more than 0.05% niobium and not more than 0.025% titanium for the endmill according to claim 1.