DE2339779B2 - Process for the production of stable wrought calcium-lead alloys with or without tin - Google Patents

Description

The invention relates to a method according to the preamble of claim 1.

Lead alloys are required for a wide variety of purposes, for example for the production of Batteries. However, their physical properties are not very favorable in terms of strength, strength stability at room temperature, and time and long-term behavior or creep resistance.

It is known that relatively stable lead-calcium and wrought lead-calcium-tin alloys can be produced by casting a lead alloy which has a calcium content of about 0.02 to about 0.1% and preferably such The tin content is such that the tin-calcium weight ratio or the relative tin content is from about 5: 1 up to 10: 1 and preferably more than 10: 1 to about 150: 1, with particularly preferred alloys is between about 16: 1 and about 40: 1 with provided that the absolute tin content is from about 0.3 to about 3.0% and preferably between 0.6 and is about 2.0%. Thereafter, the cast alloy is machined or deformed at a time that is within a limited period of time after casting, namely approximately 8 hours for the lead-calcium alloys, about 48 hours for the lead-calcium-tin alloys with a tin-calcium weight ratio from about 5: 1 to 10: 1. and about 7 days for the lead-calcium-tin alloys a tin-calcium weight ratio of more than 10: 1 to about 150: 1 (see BE-PS 7 86 140).

All contents are given in percent by weight.

Up until now, however, it was common to use a lead-calcium alloy for full curing in the state of the solid solution at elevated temperatures of z. B, 250C to be pressed (W. Hofman, "Blei und Bleilegierungen", 1962, pp. 64 and 65). It was determined, that at such deformation temperatures the desired physical properties cannot be achieved are. In particular, there was the problem that the tensile strength initially achieved was not resistant to aging but steadily deteriorated over time.

The object of the invention is to provide a method for producing a wrought lead alloy with good strength properties (at room temperature) to be specified,

which are either stable immediately after cold forming or to an even higher level over time Increase the value and then stabilize at this value.

The invention solves this problem by the method characterized in claim 1.

Refinements of the invention are characterized in the subclaims.

The length of time between casting and deformation is essential in order for lead-calcium or lead-calcium-tin wrought alloys whose strength remains stable at room temperature. In other words:.: The strength properties of the alloys according to the invention are either immediately stable at room temperature ("immediate stability"),

or they become gradual over time up to a period of between 60 and 120 days or longer better and then remain stable at room temperature (»long-term stability«). The tin to calcium weight ratio or the relative tin content is important in order to produce wrought lead alloys, which not only have the desired strength stability at room temperature, but also better in terms of Strength, heat stability and creep resistance and creep resistance are. With growing Tin-calcium weight ratio these latter properties get better and then worse again. It is also essential that the absolute Tin content is regulated and in particular kept below a maximum value, so that the strength stability is maintained results at room temperature. The alloys should preferably have a calcium content between 0.06 and 0.09 percent by weight. In relation to these preferred ranges, it should be noted that in practice the calcium concentration may not be precisely controllable. The real one The range can therefore be between 0.05 and 0.09%, for example. Fine substantial consolidation or Strengthening the alloy can be achieved by adding tin in such an amount that the Tin to calcium weight ratio or the relative proportion of tin is from 5: 1 to 10: 1. Preferably If the alloy contains enough tin that this ratio is between 10: 1 and 150: 1. Particularly cheap Results are obtained with a range between 16: 1 and 40: 1. The absolute tin switch is deceiving 0.3 to 3.0% and preferably 0.6 to 2.0% based on the weight of the alloy.

The cast alloys graze within a specific limited period of time after the Gie-Ben cold formed, which can be increased with the relative tin-calcium content. Accordingly tin-free lead-calcium alloys must be cold-formed within 8 hours after learning

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the. The tin-containing lead-calcium alloys with a tin-calcium weight ratio of 5: 1 to 10: 1, on the other hand, can be cold-formed within 48 hours after dom casting, and the tin-containing Lead-calcium alloys with a tin-calcium weight ratio from more than 10: 1 up to 150: 1 even within a period of 7 days after pouring. On the other hand, it is also closed with these two tin-containing lead-calcium legislations prefer that they be cold deformed within 8 hours of casting, because then allow better properties to be achieved.

In a method according to the invention one can opt for casting and deforming in metallurgy Use conventional continuous or discontinuous methods. Under can deform for example, rolling, extrusion, upsetting, etc. should be understood.

The following theory may contribute to the understanding of the invention, but it does not support its correctness is not dependent on:

It can be assumed that those treated according to the invention Lead-calcium and lead-calcium-tin alloy systems solidified by a process known as precipitation hardening. at In the alloys described here, calcium is much less soluble in the lead lattice than at room temperature at elevated temperatures. When you cast a lead-calcium or lead-calcium-tin alloy If it cools down to ambient temperature in an appropriate period of time, a supersaturated one results Solid solution material that contains significantly more calcium than is energetically feasible or possible. Over time, the excess calcium is deposited into the lead matrix in the form of a intermetallic component that solidifies the lead. The rate of deposition of calcium depends on the chemical composition of the alloy. A BIci-calcium-tin alloy system becomes calcium Eliminated more slowly than from a lead-calcium alloy system.

The present invention is based on the finding that previously unknown interactions between excretion and deformation. It was found that when cold working of a casting before the excretion of the excess calcium, the mechanical properties of the cold-worked piece will be immediately stable and even become stronger over time and then stable can be. However, the cast is calibrated after practically all of the excess calcium has precipitated, then the mechanical properties will change during aging at ambient conditions worse. The extent of the deterioration depends on the chemical composition and the extent of calcium precipitation prior to cold working.

As is well known in metallurgy, cold working means the mechanical deformation of a workpiece at a temperature which is so low that dislocations caused by machining are maintained, ie below the recrystallization threshold. In contrast, in the case of hot deformation, the temperature of the workpiece is so high that it is caused by the machining. Dislocations are quickly resolved. According to the present invention, there is an interaction between the dislocations of the cold deformation and the precipitated calcium, which leads to mechanical properties that are stable or even improve with aging. The best results are obtained when the degree of cold working is equivalent to a degree of deformation of 4/1 or more (ie a 1 cm thick strip is reduced by cold rolling to a thickness of ¹ A cm or less). Somewhat less noticeable improvements can also be observed if the cold deformation is less extensive.

As can be seen from the above explanations, the invention does not apply to the cold working of fresh cast lead-calcium or lead-calcium-tin alloys. Aged lead calcium and Lead-calcium-tin alloys can even after excretion of the entire calcium excess be returned to a state in which a deformation or re-deformation is possible is. This is done simply by heating such workpieces to a temperature sufficient to redissolve the excreted calcium and then return to ambient temperatures be cooled down. Melting and pouring again is not necessary. This renewal or restoration of the lead-calcium and lead-calcium-tin alloys into one for the The condition suitable for cold working is hereinafter referred to as solution heat treatment.

Solution heat treatment consists in treating a previously aged workpiece with an alloy composition of the kind discussed here to be heated to a sufficiently high temperature and for a sufficient to hold long periods of time so that a substantial portion of the calcium returns to solid solution (Mixed crystal formation) comes with the lead. If so, then in a reasonable period of time is cooled to ambient conditions, a supersaturated, containing an excess of calcium results Solid solution material just like a freshly cast material, and that of solution heat treatment Subjected workpiece will behave just like a fresh cast.

As a general guideline, it is sufficient to close the workpiece for a reasonable ZeK at the temperature glow, in which the calcium is soluble in the lead. This condition can be derived from a suitable Derive phase diagram (compare e.g. "Constitution of Binary Allovs" by Max Hansen, McGraw-Hill Publishing Co.). As a simple help in determining if the calcium has been redissolved is. the hardness or strength of the solution heat treated workpiece may coincide with that a freshly cast alloy of the same composition can be compared. Methods for Formation of supersaturated solutions or mixed crystals of calcium in lead are well known, for example from GB-PS 314 522.

The solution heat treatment method can be used on workpieces that have been stored for too long after casting have been to be hardened by cold working in the manner described here can. It is to be expected that it will also be suitable for workpieces that have previously been cold-worked after casting and have to be subjected to further cold deformation, although they are old, in which the excess calcium has already been excreted.

In the practical implementation of the invention

the workpiece is normally essentially carried out. All samples were taken on a commercial

at room temperature or with the existing standard specimen punching machine (type

ambient temperature of the respective company cold- »Tensile-Kut«).

forms. It goes without saying, however, that the meaning and the influence of the period of time both Cold working heat generated the temperature 5 see the casting and rolling on the Zugdes Workpiece will be increased somewhat. If that is the strength and tensile strength stability of space workpiece in the manner described here at temperature is in Figs. 1, 2 and 3 for alloy room temperature In environmental conditions a gene according to the invention is made clear, namely for cold working, no lead-0.08% calcium alloy (without tin), a special precautions are taken, by the cold io lead-0.08% -calcium-0.5% -tin alloy or a machining to dissipate heat generated, as this lead-0.08% -calcium-l, 0 ° / o-tin alloy necessary is. Those for realizing the results show the effect of rolling within 8 hours tried and tested and suitable ambient conditions after casting (method A), one day after Conditions are generally found in a normal pouring (method B), 7 days after pouring Workshop. All that is required is that the work 15 (procedure C), 14 days after casting (procedure after your pouring or solution treatment ren D) and 30 days after pouring (method E). The data for the tin-free lead 0.08% calcium leliche Convection can cool, typically in a yaw (Fig. 1) show that this is done within 8 hours of a few hours or less. After- rolled material after casting the lowest which the workpiece has reached a temperature of 20 tensile strength, but that temporally at room temperature it can be handled comfortably (typically temperature is immediately stable (immediate stability) than about 57 ° C), one can proceed with ben tin-free alloys for 1, 7, 14 and 30 days of cold deformation. be rolled after casting, although initially

According to FIG. 1 to 8 of the drawing and the further higher tensile strengths, which, however, are not stable over time at room temperature as the table below as preferred. After reaching a maximum example of the invention alloys in fol- lowing anywhere between 10 and 40 days, the gender way cast and deformed. For the lead tensile strength of the alloys used in all other processes, lead was removed with corrosion-free tin-free materials. Used after 240 Ta quality. The calcium content was commercially determined tensile strength data (shown in FIG. 1 not usual calcium with a purity of 99.5%) showed that tin was widely used according to method B; - and E tin-free alloys produced weaker material with a purity of 99.9%. The alloys are made as a tin-free material, which is continuously produced using a so-called pilot process A, and that is cast using the abscale caster. The poured upward trend in procedures C and D continues.
Slabs were 27 cm wide and 2 or 1.3 or 35 F i g. Figure 2 similarly shows the effect of the period between 0.6 cm thick. So that a good internal and external casting and rolling resulted in the tensile strength of the cast state, the different thickness and tensile strength stability at room temperature for ken slabs at different temperatures were determined. 5 ^e / o tin alloy that were cast, that is, the 2 cm thick castings were made at a casting temperature of 370 ° C made according to the same five procedures A through E, which was 40 ° C. Here it can be seen that a material made the 1.3 cm thick pieces at 385 ° C and the 0.6 cm thick had a tin to calcium weight ratio of about ken pieces at 400 "C. The temperatures were 5: 1 to 10: 1, for example 6.25: 1, and rolling was maintained as accurately as possible during the casting halfway 8 hours after the casting, but the coarse temperature control was on (method A), and a material that was 1 day After rolling at changes of ± 5 ° C during the length of a casting (method B), their tensile strengthening process was stopped. The alloys were cast at a rate at room temperature gradually over a period of 1.1 m / min 4 months and then the same

When deforming, it is about rolling, and reaching Werie (long-term stability). One lets

The continuously cast alloys were, however, 7, 14 and 30 days (method C, D and E)

spread to 1 mm using the following con- 50 between pouring and rolling,

constant roll caliber program rolled: 19, 13, 9, so you get alloys that match their physical

5, 3, 1.6 and 1 mm. The starting material was to improve properties for about 60 days,

continuously cast strips of 19 or 13 mm, whereupon their tensile strength at room temperature is small.

Thickness that has been cold-rolled to the final dimension.

which he did at room temperature for different 55 The dependence of the tensile strength on space-time spans had been aged, namely within temperature of the time for a lead 0.08% cal-8 Hours (method A), one day (method B), zium-1.08 «O-tin alloy, made according to method 7 Days (Method C), 14 days (Method D) and A. B, C and E are shown in Figure 3 30 days (method E). The properties of the shown. This tin-containing alloy has a tin-rolling effect Sheet metal in terms of creep resistance, 60 Kabium weight ratio between more than 10: 1 Tensile strength and creep rupture strength were determined during and about 150: 1, e.g. B. 12.5: 1. With the perpetrators Aging at room temperature for up to ren A, B and C resulted in stable tensile strength 240 days or more. The tensile strength at room temperature (long-term stability), the higher was determined using standard samples (according to was than that for the tin-free alloy according to the American standard test system ASTM) of 65 F i g. 1. These data show that there is a delay 1 inch length at a test speed of up to 7 days between pouring and the 1.27 cm min measured. The long-term tensile strength / dcformation does not degrade the properties ZcitsiandicM was tcrt on 2 inch lanpcn samples. although in principle the alloy is around

39 779

the stronger or firmer, the shorter the delay time. However, if you wait 30 days (procedure E) with rolling, a material is obtained that has a maximum tensile strength at room temperature, which is considerably lower than the tensile strength obtained with the other methods, and in this case the tensile stress then decreases very slowly over time.

F i g. 4 shows the relatively ordered behavior of the three alloys according to FIGS. 1, 2 and 3, which under were cast under identical conditions and rolled within 8 hours after casting (method A), with regard to immediate and long-term stability. Here, too, you will find that the tin-containing lead-calcium alloys have a much greater tensile strength at room temperature than that tin-free alloy.

Fig. 5 shows the unfavorable consequences on tensile strength the same three alloys according to FIGS. 1, 2 and 3 if 30 days (method E) between the Pouring and rolling. A comparison of the curves in Fi g. 4 and 5 shows how important it is that the lead-calcium and lead-calcium-tin alloys are processed shortly after casting so that stable tensile strength at room temperature results.

In Fig. 6, the tin-calcium weight ratio is below the tensile strength at room temperature for Bars 1.3, 1.9 and 2.5 cm thick were applied for lead alloys between 0.06 and Contains 0.09% calcium. This curve shows that the tin-calcium weight ratio or the relative Tin content one of the key parameters in a method according to the invention for determining is the maximum tensile strength at room temperature. The data presented show that when used of the tin-calcium weight ratio as the controlled variable is the scatter of the natural

shafts due to different chemical compositions and bar thickness disappears. Considering Fig. 6 together with the following Table shows that the tin-calcium weight ratio or the relative tin content are between should be more than 10: 1 and 150: 1, preferably between 16: 1 and 40: 1, so the tensile strength at room temperature of the aged lead-calcium-tin kneading becomes maximum. F i g. 6 also shows that in a tin-calcium mixture

ao weight ratio between 5: 1 and 10: 1 the tensile strength at room temperature of an aged tin-containing lead-calcium alloy can be improved somewhat.
The data in the following table indicate the tensile strength after aging periods of up to 1 year at room temperatures of various lead-calcium-tin wrought alloys which were produced according to method A, the relative and absolute tin contents being varied.

example

Sn / CA

Weight ratio

Sn

Weight percent

Approx

Weight percent

Aging time (days)

14th

30th

120

365

1 24: 1 2.00 0.082 8300 10 200 10 600 10 600 10 800 2 26: L 1.95 0.074 7500 8 600 - 9000 9 500 3 27: I 1.17 0.043 6100 6 900 7,300 8 900 9,300 4th 33: I 1.81 0.055 7950 9 600 10 200 10 500 10 500 5 40: 1 I 2.72 0.068 8000 8 600 - 8 800 8 900 6th . 50: I 2.47 0.049 8600 9 900 - 10 500 10 500 7th 61: I 1.29 0.021 6500 6 700 6,800 7,300 - 8th 100: I 3.00 0.030 9 148: 1 I 2.52 0.017 6700 6,800 6 900 7 200 - 10 83: 1 L 4.95 0.055 9000 10 300 10100 9600 8 500 U 115: I 6.32 0.055 9400 9 900 7900 7 200 6,300

10 500 10 500

9 100

9 100

As stated above, the data in the table in connection with Fig. 6 shows that the tin to calcium weight ratio or the relative tin content should be greater than 10: 1 to 150: 1 and that this ratio should preferably be between 16: 1 and about 40: 1 for a maximum tensile strength at room temperature for the aged alloy gives Comparing the data for Examples 1 to 9 according to the invention with those for Examples 10 and 11 which are not in fall within the preferred scope of the invention (because the absolute tin content exceeds 3.0 · / ο), one can see that the absolute tin content is between 0.3 and 3.0 Vo and preferably between 0.6 and 2.0%, based on the weight of the alloy, should be, so that the strength stability at room temperature is further guaranteed. Also give the data for Examples 1 to 3, in which the tin-calcium weight ratio or the relative tin content practically constant or similar, d. H. about 25: 1 that the strength of the lead-calcium-tin wrought alloys increases with the absolute calcium or tin content.

The other considerations in adding tin to lead-calcium alloys are illustrated in FIGS. 7 and 8, where it is shown that tin to a large extent increases the tensile strength stability of the system at elevated temperatures, for example 66 ^° C., and very significantly that Creep or creep resistance behavior improved. According to Fi g. 7, the lead alloy with a higher tin-calcium weight ratio than 10: 1 to about 150: 1, for example 14.3: 1, was practically heat-stable at the elevated temperature, while this was the case with the

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two other lead alloys with a relatively low tin to calcium weight ratio of 6.25: 1 and 0: 1 (no tin) was not the case. Fig. 8 shows that the lead alloys with a greater tin-to-potash weight ratio than 10: 1 only tear after about 70 hours at a tensile stress of 210 kp / cm *. This is in the In contrast to the tin-free alloy, which broke after half an hour.

The application of the present invention to the solution treatment of aged alloys is discussed explained by the following examples (which follow the table above):

. As an example No. 12 was a lead-0.08%> - calcium alloy by continuous casting into an ingot of 1.9 cm in thickness and 26.7 cm in width at a temperature of 370 ⁰ C and a pulling speed of about 107 cm / min poured with a surface suitable for rolling. The alloy was aged for 60 days at room temperature, which ensured complete excretion of the excess calcium. Two sections of this material were heated to a temperature of 315 ° C. for 2 hours and then cooled to room temperature. This material was rolled after aging for 1 hour and after aging for 30 days at room temperature. The rolled material was then aged for up to a year at room temperature and tested at periodic intervals. F i g. 9 shows the aging behavior of the two rolled materials. The material that was rolled after being aged for 1 hour at room temperature following the solution treatment (see curve v4 ')> had an initial strength of approximately 380 kgf / cm ² and remained on aging for the duration stable from one year. The material which had been aged for 30 days after the solution treatment (curve £ ') had an initial strength of approximately 492 kgf / cm * and then deteriorated until after 180 days it had a lower strength than the material made according to the invention.

The material subjected to the solution treatment behaved almost identically to the behavior of an in similarly treated freshly poured bar

rens. This results from a comparison of curves A ' and E' in FIG. 9 with the curves for methods A and E in FIG. 1.

As Example 13, a lead-0.065 '/ "- calcium-US ^o / o-tin alloy was continuously cast, aged and in

χ 5 in the manner explained in Example 12 of a solution heat treatment subjected. Fig. 10 shows the aging material of the two rolled samples. The sample that rolled after aging for one hour at room temperature following the solution treatment

ao (curve A '), had an initial strength of approximately 506 kgf / cm ² and reached a strength of 738 kg / cm ¹⁸ on aging after 120 days. The sample aged for 30 days at room temperature before rolling (curve EO only reached a maximum

a5 paint strength of 647 kp / cm * and then lost in strength during aging

The behavior of the two samples according to the present invention is similar to that of FIG comparable to cast and rolled materials,

the in F i g. 3 are shown. The material subjected to the solution treatment achieves a somewhat higher strength than the 0.08 ^e / o-calcium-1 ^e / o-tin alloy, which is due to the higher Sn-Ca ratio of the solution-annealed material.

The abscissa in Figs. Has 1 through 7, 9 and 10 respectively is a linear scale, while the abscissa in FIG. 8 has a logarithmic scale.

For this purpose 10 sheets of drawings

Claims (3)

Patent claims: 1. Process for the production of stable lead-calcium wrought alloys, in which a workpiece is formed from an alloy composed of 0.02 to 0.1% calcium, with or without 0.3 to 3.0% Tin, the rest lead with the usual manufacturing-related impurities, and that Workpiece is machined or deformed within a limited period of time after casting, which is less than 7 days if the tin-calcium weight ratio or the relative tin content is greater than 10: 1 up to 150: 1, less than 48 hours when that ratio from 5: 1 to! 0: 1, or less than 8 hours if the alloy is tin-free, characterized in that after casting the calcium in a supersaturated state Mixed crystals are mixed in the lead and that the workpiece is then within the limited Time is cold deformed. 2. The method according to claim 1, characterized in that the supersaturated mixed crystals can be produced in that the workpiece is cooled to room temperature after casting. 3. The method according to claim 1, characterized in that the workpiece after it has aged has been, with a sufficient to generate mixed crystals with the calcium Annealed temperature and time and then to form the supersaturated mixed crystals with the Calcium is cooled to room temperature.