Lead free free-cutting steel and its use
A technology of lead-free steel and application, applied in the field of lead-free steel
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[0075] According to a third preferred embodiment, the steel has the following approximate composition (in weight percent):
[0076] C 1
[0077] Si 0.2
[0078] Mn 0.5
[0079] P max 0.02
[0080] S 0.1
[0081] Cr 0.5
[0082] Ni 0.4
[0083] Cu 0.4
[0084] The balance is Fe and impurities that are usually present.
[0085] According to a fourth preferred embodiment, the steel has the following approximate composition (in weight percent):
[0086] C 0.9
[0087] Si 0.2
[0088] Mn 0.5
[0089] P max 0.02
[0090] S 0.1
[0091] Cr 1.5
[0092] Ni max 0.1
[0093] Cu 0.4
[0094] The balance is Fe and impurities that are usually present.
[0095] The steel according to the invention generally has a hardness of at least 850 HV1 when hardened, such as quenched, at about 800° C., and at least 600 HV1 after tempering at 300° C. for 30 minutes. The steel is also machinable, at least as good as the corresponding leaded alloy steels in terms of cutting time before b...
example 1
[0096] Example 1 - Components
[0097] Twelve different trial heats of the alloy according to the invention were produced by melting in a high frequency furnace and then casting into 270 kg ingots. To prevent cracks, the ingots were allowed to cool slowly from about 1550 °C to room temperature in an insulated environment for a period of one week before being reheated and forged into φ45 mm round bars. Before all tests were performed, the material was soft annealed at about 750°C for about 4 hours, followed by controlled cooling at a rate of about 10°C / h.
[0098] Table 1 gives the chemical composition of the test samples and the reference material (REF1) containing lead, where all figures are given in percent by weight. The reference material was manufactured by means of large-scale melting, secondary refining and continuous casting.
[0099] Table 1
[0100] sample
[0101] All components of the test samples contained max. 0.03% P, max. 0.02% N, max. 0.05% Mo, ...
example 2
[0102] Example 2 - Hardening
[0103] Samples -68 to -77, -79 and -99 in Example 1 are in the form of hollow samples with an outer diameter of 4.9mm, an inner diameter of 4.1mm and a length of 12.5mm, heated from room temperature to 800°C at a rate of 25°C / s to harden. The sample was held at 800°C for 5 minutes. Thereafter, cooling of the sample was achieved by flushing the sample with helium using a controlled cooling rate. Controlling the cooling rate was achieved by testing the hardenability of the samples using a quench dilatometer. A low cooling rate can lead to an undesired phase transformation of the austenitic phase, such as to bainite or pearlite instead of martensite, which leads to a reduction in the hardness of the material.
[0104] After heat treatment, Vickers hardness (HV1) and microstructure of the samples were investigated. exist Figure 1a with Figure 1b In , the hardness of the test material after hardening is shown as a function of the time (in sec...
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Abstract
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