Why Seamless Pipes Cost More Than Seam Pipes?

Definition of Seamless Pipe

Seamless steel pipe is a pipe without welded joints, typically formed from solid round steel through multiple roll forming passes.

Because it lacks joints, it offers superior strength and sealing properties, making it suitable for high-pressure, high-temperature, low-temperature, or negative-pressure environments. It is commonly used in the petroleum, chemical, aviation, and aerospace industries.

Definition of Seam Pipe

Welded steel pipes are made by curling steel plates or steel strips and welding them together. A noticeable weld is formed during the manufacturing process, hence the name "seam pipe".  It offers high production efficiency and low costs, and is widely used in construction, machinery, bicycles, and other fields.

Compared to seamless steel pipe, welded steel pipe has slightly lower strength and sealing properties due to the weld seam.

Cost of Seam Pipe vs. Seamless Pipe

1. Raw Material Cost Difference

Seamless pipe uses round billets (typically with a diameter 1.5-3 times the outer diameter of the pipe), achieving a raw material utilization rate of approximately 65%-75% (for example, to produce seamless pipe with an outer diameter of 108mm and a wall thickness of 6mm, a billet with a diameter of 162mm is required).

Seam pipes, on the other hand, use steel plates or strips (the width is the pipe circumference plus weld allowance), achieving a raw material utilization rate of over 90% (for example, only 340mm wide steel strip is needed to produce the same specification welded pipe).

Using 20# steel as an example, the price of seamless pipe billets is 10%-15% higher than that of welded pipe steel plates (due to the additional forging or rolling steps required).

2. Processing Cost Differences

Seamless pipe processing requires multiple steps, including piercing, rolling, and sizing (requiring significant equipment investment, with a single piercing machine costing over 5 million yuan), resulting in a processing fee of approximately 800-1200 yuan per ton.

Seam pipes, on the other hand, only require forming, welding, and sizing (requiring less equipment investment, with a single production line costing approximately 2 million yuan), resulting in a processing fee of approximately 400-600 yuan per ton.

For example, to produce 1,000 tons of pipe with an outer diameter of 219mm and a wall thickness of 8mm, the processing cost of seamless pipes is 400,000-600,000 yuan higher than that of seam pipes.

3. Efficiency and Scale Differences

The daily output of a seamless pipe line is approximately 50-80 tons (limited by billet supply), while a seam pipe line can reach 100-150 tons (continuous production is possible). This scale advantage results in lower unit costs.

For example, some factories with a seam pipe line with an annual production capacity of 100,000 tons have unit fixed costs (depreciation and labor) that are 30% lower than those of a seamless pipe line (with an annual production capacity of 50,000 tons).

Furthermore, special requirements (such as small batches and non-standard specifications) can exacerbate cost differences:

Seamless pipes require long die change times (typically 4-8 hours), increasing unit costs by 20%-30% for small batches. However, welded pipes can reduce costs for small batches through rapid die changeovers (completed within 30 minutes).

4. Additional Costs

Seamless steel pipes do not require weld inspection, saving some quality inspection costs, but the raw material (billet) cost is higher.

Seam pipes require non-destructive testing of welds (such as ultrasonic testing), which increases quality inspection costs by 5%-10%, but can be reduced through scaled production.

5. Cost Comparison in Typical Scenarios

Market Demand and Supply

Due to their high strength, corrosion resistance, and excellent pressure-bearing capacity, seamless pipes are widely used in high-end industries such as petroleum, natural gas, chemicals, and power generation.

These industries have high requirements for pipe quality and performance. Therefore, market demand for seamless steel pipes is relatively stable, but supply is relatively limited, resulting in relatively high prices.

Seam pipes are widely used in a wide range of industries, including construction, agriculture, and machinery manufacturing.

Because these industries have relatively low quality and performance requirements for pipes, the market demand for welded steel pipe is high. Furthermore, due to the simple manufacturing process and relatively abundant supply, seam pipe offers relatively low prices.

Selection Guide

For standard specifications (e.g., outer diameters 57mm-325mm) and bulk orders (≥500 tons), seamless pipe costs 30%-40% more than seam pipe.

However, in special operating conditions such as high pressure and low temperatures (where seamless construction is essential for safety), its cost advantage is outweighed by its performance advantages, making it the preferred choice.

Summary

The main reasons why seam pipe is generally cheaper than seamless pipe are its relatively simple production process and lower raw material costs. When selecting pipe material, it's important to consider the specific project requirements, budget, and performance needs. Only by choosing the right pipe material for the right application can you ensure project safety and reliability.