JPS6325054B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a drill collar material that is non-magnetic, has low thermal expansion, has high yield strength and excellent machinability, and is particularly suitable as a drill collar material for oil drilling. . Generally, non-magnetic steels are solid solution hardening type such as Cr-Ni type,
Age hardening type such as Mn-Cr-V system and Cr-Ni-P system,
The solid solution hardening type generally has a low yield point, while the age hardening type is used for long materials and large In the case of large materials such as cross-sectional materials, there are problems with heat treatment equipment, and at the same time there is a problem of decreased toughness due to long-term heating. In addition, with conventional work-hardening nonmagnetic steel, the processing temperature must be kept close to room temperature, resulting in high processing stress, and processing equipment such as rolling mills or forging machines must be large. It has the disadvantage of poor machinability. Therefore, the present inventors have developed a non-magnetic drill collar that can obtain high yield strength without requiring large-scale processing equipment, especially when manufacturing non-magnetic drill collars for oil drilling, and at the same time has improved machinability. The present invention was achieved as a result of various experimental studies aimed at obtaining magnetic steel. That is, the method for manufacturing a material for a drill collar according to the present invention is to use a high Mn non-magnetic steel as a material, and in terms of weight percentage, C and N: 0.01 to 0.5% and (C + 1.5N): 0.025-1%, Si: 2% or less,
Mn: 10-30%, Ni: 0.01-5%, Cr: 6.5-15
%, Mo: 0.01 to 3%, S: 0.2% or less,
If necessary, to further improve machinability,
Contains one or two of Ca: 0.0005 to 0.02%, Te: 0.05 to 0.3%, and one or two of W, Co, and Cu as required for the above basic steel. Contains 3% or less of two or more types in total,
Similarly, if necessary, 650 It is characterized by performing finishing processing at a processing rate of 5% or more but 20% or less in a temperature range of ~950℃. Hereinafter, the reason for limiting the chemical composition range (weight %) of the target steel in the method for manufacturing a material for a drill collar according to the present invention will be explained. C, N: 0.01~0.5% and (C+1.5N): 0.025~
1% C and N are elements that stabilize austenite and at the same time contribute to solid solution strengthening, each with 0.01
% or more is necessary. However, C
is the coefficient of thermal expansion, and N is the upper limit of 0.5% for steel manufacturing reasons. In addition, the influence of C and N on the degree of strengthening of non-magnetic steel is (C + 1.5N)
can be organized as a coefficient, and at 0.2% yield strength
To obtain a strength of 50Kgf/mm2 or ^more , 0.025%
It is necessary to contain the above amount. However, if the content exceeds 1%, the toughness deteriorates, which is not preferable. Si: 2% or less Si is an element necessary for improving strength, but 2%
If the content exceeds 2%, the toughness will deteriorate, so the upper limit is set at 2%. Mn: 10-30% Mn is an element necessary to obtain a stable austenite phase and nonmagnetism, and for this purpose it is necessary to contain it in an amount of 10% or more. However, 30
If the content exceeds 30%, the improvement in strength and toughness will be saturated, so the content should be 30% or less. In this case, a more preferable range is 15-25%. Ni: 0.01 to 5% Ni is an effective element for stabilizing austenite and improving toughness, and is added in an amount of at least 0.01%. However, if it exceeds 5%, it is not only excessive for stabilizing austenite, but also causes a significant price increase, so it is limited to a range of 0.01 to 5%. Mo: 0.01 to 3% Mo is an effective element for improving the strength and corrosion resistance of austenite, and at least
Add 0.01% or more. However, if it exceeds 3%, the toughness deteriorates, so it is limited to a range of 0.01 to 3%. Cr: 6.5-15% Cr makes the austenite of steel containing Mn-Ni extremely stable, and also increases work hardening by reducing stacking fault energy and obtains higher yield strength. It is an essential element. In order to improve these effects and corrosion resistance, the content should be 6.5% or more. However, the content is 15%
If it exceeds this value, martensite formation occurs and increases the magnetic permeability of the steel, making it undesirable as a non-magnetic steel. Therefore, the upper limit is set at 15%. S: 0.2% or less S is an element necessary to improve the machinability of steel. In other words, high Mn nonmagnetic steel has a high cutting temperature and required a heat-resistant cutting tool, but the inclusion of S can lower the cutting temperature and greatly contribute to improving machinability. . However, if added in large amounts, processability and mechanical properties will deteriorate, so the upper limit is set at 0.2%. One or two of Ca: 0.0005-0.02%, Te: 0.05-0.3% Both Ca and Te are effective elements for improving the machinability of steel, and Te is a sulfide nonmetal. Although it is an effective element for improving delayed fracture properties by controlling inclusion morphology, too much Ca content deteriorates the toughness of the steel, and too much He content reduces the workability of the steel. If included, 0.0005~
Range of 0.02%, 0.05~ when containing Te
The range shall be 0.3%. In addition, the addition of the following elements does not interfere with the desired properties of the steel of the present invention. One or more of W, Co, and Cu in a total of 3% or less W, Co, and Cu are all effective elements for improving the strength of austenite, but the total amount exceeds 3%. Since this results in deterioration of toughness, if it is included, the upper limit should be 3%. Moreover, a more preferable range in this case is 0.2 to 2.5%. One or more of Nb, Ti, V, and Zr in a total of 1% or less These elements are all effective in improving the strength of austenitic base and improving mechanical properties by refining grains, especially improving toughness. However, if the total content exceeds 1%, toughness and machinability will deteriorate, so if it is included, the upper limit is set to 1%. In addition, when considering the weldability of steel, P
It is more desirable to suppress the content to 0.08% or less. When manufacturing steel with the above chemical composition, for example, a melting furnace such as a converter or an electric furnace is used, and if necessary, a vacuum degassing device is used to melt the molten steel, which is then turned into billets in an ingot mold. Or cast into slabs by continuous casting. Subsequently, the steel slab or slab is more preferably processed at a processing rate of 5% at a temperature range of 650 to 950°C.
Processing such as rolling or forging is applied to the steel material to a desired shape. and,
It is more desirable that the cooling after processing be performed at a level higher than air cooling. The attached drawing is a graph showing the results of investigating the effects of processing temperature and processing rate on the mechanical properties of steel, in this case 0.3% (C + 1.5N) - 0.5%.
Si-19%Mn-0.05%S-1.7%Ni-12.0%Cr-0.5
%Mo steel is used as a test material, and shows the relationship between the working rate and finishing temperature and mechanical properties when air-cooled after rolling. As shown in the figure, by setting the rolling finishing temperature to 650 to 950℃ and adding processing at a processing rate of 5% or more, the 0.2% proof stress is 50Kgf/mm ²
A non-magnetic steel having excellent mechanical properties with an elongation of 20% or more can be obtained. On the other hand, when the finishing rolling temperature exceeds 950°C, the 0.2% yield strength decreases significantly. In addition, when the finishing temperature of rolling is less than 650℃, the elongation is 20% when the processing rate exceeds 5%.
% or less, and processing becomes difficult. Furthermore, if the processing rate exceeds 20%, the 0.2% proof stress becomes too large and the processing load increases. Therefore,
The processing temperature is preferably 650 to 950°C, and the processing rate is preferably in the range of 5% or more and 20% or less. Next, examples of the present invention will be described. First, it is melted in an electric furnace to have the chemical composition shown in Table 1, then processed into a 250 x 300 mm steel billet by blooming rolling, and then finished into a product shape with a diameter of 200 mm. The final pass was similarly rolled at each temperature shown in Table 1. Thereafter, a test piece was cut out from the product and its mechanical properties were examined, and the same results shown in Table 1 were obtained. The results of measuring magnetic permeability are also shown.

【table】

[Table] Comparative examples No. 12 and 13 shown in Table 1 are for steel that belongs to the so-called cold work hardening type, and when processed at around room temperature, the yield strength is 60 at 0.2% yield strength.
Although it is possible to obtain a good yield strength of Kgf/mm ² or more, it requires large processing equipment and has the problem that uniform processing is difficult for long pieces with large cross-sections. . In addition, as shown in Table 1, when the rolling finishing temperature is 700℃, 0.2%
The yield strength is as low as 40 to 45 kgf/ ^mm2 . On the other hand, in invention examples No. 1 to 3, all
It is clear that the steel exhibits a high yield strength with a 0.2% yield strength of 60 Kgf/mm ² or more, and at the same time has a sufficiently low magnetic permeability, making it an excellent non-magnetic steel for drill collars. In addition, Nos. 6, 7, and 8, which contain W, Co, and Nb in the basic component steel, exhibited higher yield strength and elongation, and when the rolling finishing temperature was relatively high as in No. 6. However, high yield strength can be obtained. However, as shown in Comparative Examples Nos. 2' and 8', it is clear that when the finishing rolling temperature is set too high as 1000°C, the 0.2% yield strength is significantly lowered. Next, the steels of Invention Examples Nos. 2, 4, and 5 and Comparative Examples Nos. 12 and 13 were tested for machinability. Table 2 shows the test conditions at this time. Further, the test results are shown in Table 3. In addition, to judge the tool life, V _Bnax =
The cutting time was set to 0.3 mm.

【table】

[Table] As shown in Table 3, it is clear that the steels of the invention examples have several times longer tool life and considerably superior machinability than the steels of the comparative examples.
It is clear that the machinability of the steels of Invention Examples No. 4 and 5 containing Te is further improved. As explained above, according to the present invention, the material is non-magnetic, has low thermal expansion, has high yield strength, and has excellent machinability, and requires particularly large processing equipment and heat treatment equipment. It has the remarkable effect that it is possible to obtain a high yield strength without any damage, and in particular, it is possible to obtain a material suitable for drill collars for oil drilling.

[Brief explanation of the drawing]

The drawing is a graph showing an example of the results of investigating the effects of finishing rolling temperature and working rate on the mechanical properties of high-Mn non-magnetic steel.

Claims (1)

[Claims] 1% by weight, C, N: 0.01 to 0.5%, and (C
+1.5N): 0.025 to 1%, Si: 2% or less, Mn: 10
~30%, Ni: 0.01~5%, Cr: 6.5~15%, Mo:
0.01 to 3%, S: 0.2% or less, and the remainder substantially consists of Fe, 650 to 3%.
A method for manufacturing a material for a drill collar, characterized by performing finishing processing at a processing rate of 5% or more and 20% or less in a temperature range of 950°C. 2% by weight, C, N: 0.01-0.5% and (C
+1.5N): 0.025 to 1%, Si: 2% or less, Mn: 10
~30%, Ni: 0.01~5%, Cr: 6.5~15%, Mo:
0.01-3%, S: 0.2% or less, and Ca: 0.0005
~0.02%, Te: 0.05~0.3%, or two of them, with the remainder essentially consisting of Fe, with a processing rate of 5% or more in the temperature range of 650~950℃ A method for manufacturing a material for drill collars, characterized by applying a finishing process of 20% or less. 3% by weight, C, N: 0.01-0.5% and (C
+1.5N): 0.025 to 1%, Si: 2% or less, Mn: 10
~30%, Ni: 0.01~5%, Cr: 6.5~15%, Mo:
0.01-3%, S: 0.2% or less, and W, Co, Cu
A processing rate of 5% or more and 20% or less in a temperature range of 650 to 950°C for steel slabs or slabs containing one or more of the following in a total amount of 3% or less, with the remainder substantially consisting of Fe. A method for manufacturing a material for a drill collar, characterized by subjecting it to a finishing process. 4% by weight, C, N: 0.01-0.5% and (C
+1.5N): 0.025 to 1%, Si: 2% or less, Mn: 10
~30%, Ni: 0.01~5%, Cr: 6.5~15%, Mo:
0.01-3%, S: 0.2% or less, and Nb, Ti,
One or more of V, Zr in total 1
% or less, with the remainder substantially consisting of Fe, for drill collars characterized by finishing finishing at a processing rate of 5% to 20% in a temperature range of 650 to 950°C. How the material is manufactured. 5% by weight, C, N: 0.01-0.5% and (C
+1.5N): 0.025 to 1%, Si: 2% or less, Mn: 10
~30%, Ni: 0.01~5%, Cr: 6.5~15%, Mo:
0.01-3%, S: 0.2% or less, and Ca: 0.0005
~0.02%, Te: 0.05~0.3%, and one or more of W, Co, and Cu in a total of 3% or less, and the remainder is substantially
650 to 950℃ for steel slabs or slabs made of Fe
A method for manufacturing a material for a drill collar, characterized by performing finishing processing at a processing rate of 5% or more and 20% or less in a temperature range of . 6% by weight, C, N: 0.01-0.5% and (C
+1.5N): 0.025 to 1%, Si: 2% or less, Mn: 10
~30%, Ni: 0.01~5%, Cr: 6.5~15%, Mo:
0.01-3%, S: 0.2% or less, and Ca: 0.0005
~0.02%, one or two of Te: 0.05 to 0.3%, one or more of W, Co, and Cu in a total of 3% or less, and Nb, Ti, V, and Zr. A processing rate of 5% or more in a temperature range of 650 to 950°C for steel slabs or slabs containing one or more of these in a total of 1% or less, with the remainder substantially consisting of Fe20
A method for manufacturing a material for a drill collar, characterized by applying a finishing process of % or less.